CONTROLLABLE SLIPPERY POLYMER SURFACES

RELATED APPLICATIONS

[0001] This application claims the benefit of priority to co-pending United States Provisional Application Serial No. 63/358,518, filed July 5, 2022, the contents of which is incorporated by reference.

COPYRIGHT NOTICE

[0002] This patent disclosure may contain material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the U.S. Patent and Trademark Office patent file or records, but otherwise reserves any and all copyright rights.

FIELD OF THE INVENTION

[0003] The instant application relates to slippery polymer surfaces. In particular, the instant application relates to controllable slippery polymer surfaces.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0004] This invention was made with government support under N00014-17-1-2913 and N00014-15-1-2323 awarded by U.S. Office of Naval Research (NAVY/ONR) and under DE- SC0005247 awarded by U.S. Department of Energy (DOE). The government has certain rights in this invention.

BACKGROUND

[0005] Polymer materials with oils dispersed within the bulk of the polymer can be used as repellant or fouling-release coatings. One challenge in the production of slippery surfaces has been to prepare them over large surfaces in a quick and efficient process. An additional challenge has been to identify surface coatings that can remain slippery for long periods of time, particularly when exposed to dynamic flow conditions. A further desirable attribute is the ability to apply slippery coatings readily and securely to a range of underlying surfaces. SUMMARY

[0006] In one aspect, an article includes a polymer layer under an external force causing the polymer layer to be under a first compressive mechanical stress; and a lubricating liquid within the polymer layer, the lubricating liquid being at a concentration within the polymer layer such that the lubricating liquid forms a stable overlayer over the surface of the polymer layer when the polymer layer is under the external force and the lubricating liquid does not form the stable overlayer over the surface of the polymer layer when the polymer layer is not under compressive stress.

[0007] In some embodiments, the polymer layer is formed by adding the lubricating liquid to one or more polymer precursors followed by curing the polymer precursors.

[0008] In some embodiments, the article further includes a substrate under tension, the polymer layer is disposed on the substrate, and the external force on the polymer layer is applied by the tension of the substrate.

[0009] In some embodiments, the polymer layer is formed by adding the lubricating liquid to one or more polymer precursors and applying the lubricating liquid and one or more polymers to the substrate, followed by curing the polymer precursors.

[0010] In some embodiments, the substrate is under an external tension caused by an external tensile force during curing of the polymer layer, the external tension being greater than the tension.

[0011] In some embodiments, releasing the external tensile force causes the substrate to change from the external tension to the tension.

[0012] In some embodiments, the external tensile force is caused by stretching the substrate in at least one direction.

[0013] In some embodiments, the external tensile force is caused by compressing the substrate in at least one direction.

[0014] In some embodiments, the external tensile force is caused by stretching the substrate in two directions.

[0015] In some embodiments, the external tensile force is caused by compressing the substrate in at least two directions.

[0016] In some embodiments, the external tensile force is caused by radially expanding the substrate. [0017] In some embodiments, the external tensile force is caused by radially compressing the substrate.

[0018] In some embodiments, the external tensile force is caused by a stimulus applied to the substrate.

[0019] In some embodiments, the stimulus is selected from one or more of light, chemical, electromagnetic, thermal, shape memory, pressure, or mechanical stimulus. [0020] In some embodiments, the external force applied by the substrate is a radial force.

[0021] In some embodiments, the external force applied by the substrate includes a component in the direction substantially parallel to a surface of the substrate on which the polymer layer is disposed.

[0022] In some embodiments, the external force applied by the substrate includes a component in the direction substantially perpendicular to a surface of the substrate on which the polymer layer is disposed.

[0023] In some embodiments, the substrate includes a stretchable material.

[0024] In some embodiments, the substrate includes an elastomer.

[0025] In some embodiments, the substrate includes one or more of silicone rubber, polyurethane, polyisoprene, polyethylene, polybutadiene, nitrile rubber, ethylene propylene rubber (EPM, EPDM), neoprene rubber, and fluoroelastomers.

[0026] In some embodiments, the external force includes a component in a direction parallel with the surface of the polymer layer on which the stable liquid overlayer is formed. [0027] In some embodiments, the external force includes a compressive external force and the first compressive mechanical stress includes a component in a direction parallel to the external force.

[0028] In some embodiments, the external force is a stretching external force and the first compressive mechanical stress includes a component in a direction perpendicular to the external force.

[0029] In some embodiments, the external force is a compressive mechanical force and the polymer is under a tensile mechanical stress including a component in a direction perpendicular to the external force.

[0030] In some embodiments, the external force is caused by stretching the polymer layer.

[0031] In some embodiments, the external force is caused by inflation.

[0032] In some embodiments, the inflation is pneumatic inflation. [0033] In some embodiments, the external force is caused by flow induced pressure. [0034] In some embodiments, the first compressive mechanical stress is uniaxial.

[0035] In some embodiments, the first compressive mechanical stress is biaxial.

[0036] In some embodiments, the first compressive mechanical stress is radial.

[0037] In some embodiments, the external force is caused by applying a stimulus to the polymer layer.

[0038] In some embodiments, the stimulus is selected from one or more of light, chemical, electromagnetic, thermal, shape memory, pressure, or mechanical stimulus.

[0039] In some embodiments, the polymer includes a shape memory alloy, and the first compressive mechanical stress is caused by a shape change of the shape memory alloy.

[0040] In some embodiments, the lubricating liquid includes one or more of silicone oils, siloxanes, silicate esters, mineral oils, hydrocarbons, halogenated hydrocarbons liquid, polyalphaolefins, perfluorocarbons, polyfluoroalkyl ethers, polyolefins, esters with long alkyl chains, polyalkylene glycols, or polyphenyl ethers, perfluorinated liquids, and partially fluorinated liquids.

[0041] In some embodiments, the lubricating liquid includes one or more of alkanes, olefins, saturated alkanes, and unsaturated olefins.

[0042] In some embodiments, the lubricating liquid includes one or more of halogenated alkanes, halogenated olefins, and halogenated aromatic compounds.

[0043] In some embodiments, the lubricating liquid includes one or more of fluorocarbons, perfluorocarbons, hydrofluorocarbons, hydrofluorocarbon-oligomers, compounds having partially fluorinated ponytails, partially fluorinated oils, partially fluorinated greases, fluorosilicones, tertiary perfluoroalkylamines (such as perfluorotri-n- pentylamine, FC-70, perfluorotri-n-butylamine FC-40, etc. ), perfluoroalkylsulfides and perfluoroalkylsulfoxides, perfluoroalkylethers, perfluorocycloethers (like FC-77) and perfluoropolyethers (such as KRYTOX family of lubricants by DuPont), perfluoroalkylphosphines and perfluoroalkylphosphineoxides, perfluorohexyl-octane, perfluorohexyl-ethane, perfluorobutyl-butane, perflurophenanthren, perfluorooctane, perfluorophenathrene, and their analogues, homologues, oligomers, polymers.

[0044] In some embodiments, the polymer layer includes one or more of silicone rubber, fluorosilicone, polydimethylsiloxane, vinyl methyl silicone, polyurethane, natural and synthetic polyisoprenes, polyethylene, polybutadiene, nitrile rubber, polyacrylic rubber, ethylene propylene rubber (EPM, EPDM), neoprene rubber, perfluoroelastomers, polyether block amides (PEBA), chlorosulfonated polyethylene, ethylene-vinyl acetate, polyether urethane, perfluorocarbon rubber, fluorinated hydrocarbon.

[0045] In some embodiments, the polymer includes carbon black, titanium oxide, silica, alumina, nanoparticles, or a combination thereof.

[0046] In some embodiments, the polymer layer includes a porous polymer layer.

[0047] In one aspect, an article includes a substrate under tension; a polymer layer on the substrate; and a lubricating liquid within the polymer layer, where the lubricating liquid is at a concentration within the polymer layer such that no stable overlayer is formed over a surface of the polymer layer, and the substrate is configured to cause a first compressive mechanical stress on the polymer layer when the tension is released, where the first compressive mechanical stress is sufficient to cause the lubricating liquid to form a stable overlayer on the polymer layer.

[0048] In some embodiments, when the tension is released, the substrate is under a residual tension that is less than the tension.

[0049] In some embodiments, the tension includes a component in a direction parallel with a surface of the substrate.

[0050] In some embodiments, the first compressive mechanical stress includes a component in the direction parallel with a surface of the substrate.

[0051] In some embodiments, the tension is caused by stretching the polymer layer.

[0052] In some embodiments, the tension is caused by inflation.

[0053] In some embodiments, the inflation is pneumatic inflation.

[0054] In some embodiments, the tension is caused by flow induced pressure.

[0055] In some embodiments, the first compressive mechanical stress is uniaxial.

[0056] In some embodiments, the first compressive mechanical stress is biaxial.

[0057] In some embodiments, the first compressive mechanical stress is radial.

[0058] In some embodiments, the tension is caused by applying a stimulus to the substrate.

[0059] In some embodiments, the stimulus is selected from one or more of light, chemical, electromagnetic, thermal, shape memory, pressure, or mechanical stimulus. [0060] In some embodiments, the substrate includes a shape memory alloy, and the first compressive mechanical stress is caused by a shape change of the shape memory alloy. [0061] In some embodiments, the polymer layer is formed by adding the lubricating liquid to one or more polymer precursors and applying the lubricating liquid and one or more polymers to the substrate, followed by curing the polymer precursors.

[0062] In some embodiments, the substrate is under an external tension caused by an external tensile force during curing of the polymer layer, and the external tension is greater than the tension.

[0063] In some embodiments, releasing the external tensile force causes the substrate to change from the external tension to the tension.

[0064] In some embodiments, the external tension is the same as the tension.

[0065] In some embodiments, the external tension is different than the tension.

[0066] In some embodiments, the external tensile force is caused by stretching the substrate in at least one direction.

[0067] In some embodiments, the external tensile force is caused by compressing the substrate in at least one direction.

[0068] In some embodiments, the external tensile force is caused by stretching the substrate in two directions.

[0069] In some embodiments, the external tensile force is caused by compressing the substrate in at least two directions.

[0070] In some embodiments, the external tensile force is caused by radially expanding the substrate.

[0071] In some embodiments, the external tensile force is caused by radially compressing the substrate.

[0072] In some embodiments, the external tensile force is caused by a stimulus.

[0073] In some embodiments, the stimulus is selected from one or more of light, chemical, electromagnetic, thermal, shape memory, pressure, or mechanical stimulus.

[0074] In some embodiments, the lubricating liquid includes one or more of silicone oils, siloxanes, silicate esters, mineral oils, hydrocarbons, halogenated hydrocarbons liquid, polyalphaolefins, perfluorocarbons, polyfluoroalkyl ethers, polyolefins, esters with long alkyl chains, polyalkylene glycols, or polyphenyl ethers, perfluorinated liquids, and partially fluorinated liquids.

[0075] In some embodiments, the lubricating liquid includes one or more of alkanes, olefins, saturated alkanes, and unsaturated olefins. [0076] In some embodiments, the lubricating liquid includes one or more of halogenated alkanes, halogenated olefins, and halogenated aromatic compounds.

[0077] In some embodiments, the lubricating liquid includes one or more of fluorocarbons, perfluorocarbons, hydrofluorocarbons, hydrofluorocarbon-oligomers, compounds having partially fluorinated ponytails, partially fluorinated oils, partially fluorinated greases, fluorosilicones, tertiary perfluoroalkylamines (such as perfluorotri-n- pentylamine, FC-70, perfluorotri-n-butylamine FC-40, etc. ), perfluoroalkylsulfides and perfluoroalkylsulfoxides, perfluoroalkylethers, perfluorocycloethers (like FC-77) and perfluoropolyethers (such as KRYTOX family of lubricants by DuPont), perfluoroalkylphosphines and perfluoroalkylphosphineoxides, perfluorohexyl-octane, perfluorohexyl-ethane, perfluorobutyl-butane, perflurophenanthren, perfluorooctane, perfluorophenathrene, and their analogues, homologues, oligomers, polymers.

[0078] In some embodiments, the polymer layer includes one or more of silicone rubber, fluorosilicone, polydimethylsiloxane, vinyl methyl silicone, polyurethane, natural and synthetic polyisoprenes, polyethylene, polybutadiene, nitrile rubber, polyacrylic rubber, ethylene propylene rubber (EPM, EPDM), neoprene rubber, perfluoroelastomers, polyether block amides (PEBA), chlorosulfonated polyethylene, ethylene-vinyl acetate, polyether urethane, perfluorocarbon rubber, fluorinated hydrocarbon.

[0079] In some embodiments, the polymer includes carbon black, titanium oxide, silica, alumina, nanoparticles, or a combination thereof.

[0080] In some embodiments, the polymer layer includes a porous polymer layer.

[0081] In some embodiments, the substrate includes a stretchable material.

[0082] In some embodiments, the substrate includes an elastomer.

[0083] In some embodiments, the substrate includes one or more of silicone rubber, polyurethane, polyisoprene, polyethylene, polybutadiene, nitrile rubber, ethylene propylene rubber (EPM, EPDM), neoprene rubber, and fluoroelastomers.

[0084] In one aspect, a method of making an article includes: adding a lubricating liquid to one or more polymer precursors; and curing the one or more polymer precursors to form a polymer layer dispersed with the lubricating liquid, wherein the lubricating liquid is added to the polymer precursors at a concentration such that, after forming the polymer layer the lubricating liquid does not form a stable overlayer on a surface of the polymer layer; and applying an external force to the polymer layer such that the polymer layer is under a first compressive mechanical stress sufficient to cause the lubricating liquid to form the stable overlayer on the surface of the polymer layer.

[0085] In some embodiments, the external force includes a component in a direction parallel with the surface of the polymer layer on which the stable overlayer is formed. [0086] In some embodiments, the external force includes a compressive external force and the first compressive mechanical stress includes a component in a direction parallel to the external force.

[0087] In some embodiments, the external force is a stretching external force and the first compressive mechanical stress includes a component in a direction perpendicular to the external force.

[0088] In some embodiments, the external force is a compressive mechanical force and the polymer is under a tensile mechanical stress including a component in a direction perpendicular to the external force.

[0089] In some embodiments, the external force is caused by stretching the polymer layer.

[0090] In some embodiments, the external force is caused by inflation.

[0091] In some embodiments, the inflation is pneumatic inflation.

[0092] In some embodiments, the external force is caused by flow induced pressure.

[0093] In some embodiments, the first compressive mechanical stress is uniaxial.

[0094] In some embodiments, the first compressive mechanical stress is biaxial.

[0095] In some embodiments, the first compressive mechanical stress is radial.

[0096] In some embodiments, the external force is caused by applying a stimulus to the polymer layer.

[0097] In some embodiments, the stimulus is selected from one or more of light, chemical, electromagnetic, thermal, shape memory, pressure, or mechanical stimulus.

[0098] In some embodiments, the polymer includes a shape memory alloy, and the first compressive mechanical stress is caused by a shape change of the shape memory alloy. [0099] In some embodiments, the lubricating liquid includes one or more of silicone oils, siloxanes, silicate esters, mineral oils, hydrocarbons, halogenated hydrocarbons liquid, polyalphaolefins, perfluorocarbons, polyfluoroalkyl ethers, polyolefins, esters with long alkyl chains, polyalkylene glycols, or polyphenyl ethers, perfluorinated liquids, and partially fluorinated liquids. [0100] In some embodiments, the lubricating liquid includes one or more of alkanes, olefins, saturated alkanes, and unsaturated olefins.

[0101] In some embodiments, the lubricating liquid includes one or more of halogenated alkanes, halogenated olefins, and halogenated aromatic compounds.

[0102] In some embodiments, the lubricating liquid includes one or more of fluorocarbons, perfluorocarbons, hydrofluorocarbons, hydrofluorocarbon-oligomers, compounds having partially fluorinated ponytails, partially fluorinated oils, partially fluorinated greases, fluorosilicones, tertiary perfluoroalkylamines (such as perfluorotri-n- pentylamine, FC-70, perfluorotri-n-butylamine FC-40, etc. ), perfluoroalkylsulfides and perfluoroalkylsulfoxides, perfluoroalkylethers, perfluorocycloethers (like FC-77) and perfluoropolyethers (such as KRYTOX family of lubricants by DuPont), perfluoroalkylphosphines and perfluoroalkylphosphineoxides, perfluorohexyl-octane, perfluorohexyl-ethane, perfluorobutyl-butane, perflurophenanthren, perfluorooctane, perfluorophenathrene, and their analogues, homologues, oligomers, polymers.

[0103] In some embodiments, the polymer layer includes one or more of silicone rubber, fluorosilicone, polydimethylsiloxane, vinyl methyl silicone, polyurethane, natural and synthetic polyisoprenes, polyethylene, polybutadiene, nitrile rubber, polyacrylic rubber, ethylene propylene rubber (EPM, EPDM), neoprene rubber, perfluoroelastomers, polyether block amides (PEBA), chlorosulfonated polyethylene, ethylene-vinyl acetate, polyether urethane, perfluorocarbon rubber, fluorinated hydrocarbon.

[0104] In some embodiments, the polymer includes carbon black, titanium oxide, silica, alumina, nanoparticles, or a combination thereof.

[0105] In some embodiments, the polymer layer includes a porous polymer layer.

[0106] In one aspect, a method of making an article includes providing a substrate under an external tension caused by an external force; and forming a polymer layer on the substrate under the external tension by: adding a lubricating liquid to one or more polymer precursors, and curing the one or more polymer precursors on the substrate under the external tension to form the polymer layer dispersed with the lubricating liquid on the substrate, wherein the lubricating liquid is added to the polymer precursors at a concentration such that, after forming the polymer layer: the lubricating liquid does not form a stable overlayer on a surface of the polymer layer while the substrate is under the external tension, and releasing the external force causes the polymer layer to be under a first compressive mechanical stress resulting from the residual tension of the substrate, and the first compressive mechanical stress is sufficient to cause the lubricating liquid to form a stable overlayer on a surface of the polymer layer.

[0107] In some embodiments, the method further includes forming a stable overlayer of lubricating liquid on the surface of the polymer layer by releasing the external force on the substrate such that the polymer layer is caused to be under a first compressive mechanical stress resulting from a residual tension of the substrate, and the first compressive mechanical stress is sufficient to cause the lubricating liquid to form the stable overlayer on the surface of the polymer layer.

[0108] In some embodiments, the residual tension that is less than the external tension.

[0109] In some embodiments, the method further includes applying a second external force to the substrate such that the stable overlayer is absorbed by the polymer layer.

[0110] In some embodiments, the external tension includes a component in a direction parallel with a surface of the substrate.

[OHl] In some embodiments, the first compressive mechanical stress includes a component in the direction parallel with a surface of the substrate.

[0112] In some embodiments, the first compressive mechanical stress is uniaxial.

[0113] In some embodiments, the first compressive mechanical stress is biaxial.

[0114] In some embodiments, the external tension is caused by stretching the substrate in at least one direction.

[0115] In some embodiments, the external tension is caused by compressing the substrate in at least one direction.

[0116] In some embodiments, the external tension is caused by stretching the substrate in two directions.

[0117] In some embodiments, the external tension is caused by compressing the substrate in at least two directions.

[0118] In some embodiments, the external tension is caused by radially expanding the substrate.

[0119] In some embodiments, the external tension is caused by radially compressing the substrate.

[0120] In some embodiments, the external tension is caused by a stimulus.

[0121] In some embodiments, the stimulus is selected from one or more of light, chemical, electromagnetic, thermal, shape memory, pressure, or mechanical stimulus. [0122] In some embodiments, the lubricating liquid includes one or more of silicone oils, siloxanes, silicate esters, mineral oils, hydrocarbons, halogenated hydrocarbons liquid, polyalphaolefins, perfluorocarbons, polyfluoroalkyl ethers, polyolefins, esters with long alkyl chains, polyalkylene glycols, or polyphenyl ethers, perfluorinated liquids, and partially fluorinated liquids.

[0123] In some embodiments, the lubricating liquid includes one or more of alkanes, olefins, saturated alkanes, and unsaturated olefins.

[0124] In some embodiments, the lubricating liquid includes one or more of halogenated alkanes, halogenated olefins, and halogenated aromatic compounds.

[0125] In some embodiments, the lubricating liquid includes one or more of fluorocarbons, perfluorocarbons, hydrofluorocarbons, hydrofluorocarbon-oligomers, compounds having partially fluorinated ponytails, partially fluorinated oils, partially fluorinated greases, fluorosilicones, tertiary perfluoroalkylamines (such as perfluorotri-n- pentylamine, FC-70, perfluorotri-n-butylamine FC-40, etc. ), perfluoroalkylsulfides and perfluoroalkylsulfoxides, perfluoroalkylethers, perfluorocycloethers (like FC-77) and perfluoropolyethers (such as KRYTOX family of lubricants by DuPont), perfluoroalkylphosphines and perfluoroalkylphosphineoxides, perfluorohexyl-octane, perfluorohexyl-ethane, perfluorobutyl-butane, perflurophenanthren, perfluorooctane, perfluorophenathrene, and their analogues, homologues, oligomers, polymers.

[0126] In some embodiments, the polymer layer includes one or more of silicone rubber, fluorosilicone, polydimethylsiloxane, vinyl methyl silicone, polyurethane, natural and synthetic polyisoprenes, polyethylene, polybutadiene, nitrile rubber, polyacrylic rubber, ethylene propylene rubber (EPM, EPDM), neoprene rubber, perfluoroelastomers, polyether block amides (PEBA), chlorosulfonated polyethylene, ethylene-vinyl acetate, polyether urethane, perfluorocarbon rubber, fluorinated hydrocarbon.

[0127] In some embodiments, the polymer includes carbon black, titanium oxide, silica, alumina, nanoparticles, or a combination thereof.

[0128] In some embodiments, the polymer layer includes a porous polymer layer.

[0129] In one aspect, a method includes: providing an article including a polymer layer and a lubricating liquid within the polymer layer at a concentration such that the lubricating liquid does not form a stable overlayer over a surface of the polymer layer when the polymer layer is not under compressive stress; and applying an external force to the polymer layer such that the polymer layer is under a first compressive mechanical stress sufficient to cause the lubricating liquid to form a stable overlayer on the surface of the polymer layer.

[0130] In some embodiments, the article further includes a substrate under tension, and the polymer layer is disposed on the substrate and the external force on the polymer layer is applied by the tension of the substrate.

[0131] In some embodiments, the external force is caused by stretching the substrate in at least one direction.

[0132] In some embodiments, the external force is caused by compressing the substrate in at least one direction.

[0133] In some embodiments, the external force is caused by stretching the substrate in two directions.

[0134] In some embodiments, the external force is caused by compressing the substrate in at least two directions.

[0135] In some embodiments, the external force is caused by radially expanding the substrate.

[0136] In some embodiments, the external force is caused by radially compressing the substrate.

[0137] In some embodiments, the external force is caused by a stimulus applied to the substrate.

[0138] In some embodiments, the stimulus is selected from one or more of light, chemical, electromagnetic, thermal, shape memory, pressure, or mechanical stimulus. [0139] In some embodiments, the external force applied by the substrate is a radial force.

[0140] In some embodiments, the external force applied by the substrate includes a component in the direction substantially parallel to a surface of the substrate on which the polymer layer is disposed.

[0141] In some embodiments, the external force applied by the substrate includes a component in the direction substantially perpendicular to a surface of the substrate on which the polymer layer is disposed.

[0142] In some embodiments, the substrate includes a stretchable material.

[0143] In some embodiments, the substrate includes an elastomer.

[0144] In some embodiments, the substrate includes one or more of silicone rubber, polyurethane, polyisoprene, polyethylene, polybutadiene, nitrile rubber, ethylene propylene rubber (EPM, EPDM), neoprene rubber, and fluoroelastomers. [0145] In some embodiments, the external force includes a component in a direction parallel with the surface of the polymer layer on which the stable liquid overlayer is formed. [0146] In some embodiments, the external force includes a compressive external force and the first compressive mechanical stress includes a component in a direction parallel to the external force.

[0147] In some embodiments, the external force is a stretching external force and the first compressive mechanical stress includes a component in a direction perpendicular to the external force.

[0148] In some embodiments, the external force is a compressive mechanical force and the polymer is under a tensile mechanical stress including a component in a direction perpendicular to the external force.

[0149] In some embodiments, the external force is caused by stretching the polymer layer.

[0150] In some embodiments, the external force is caused by inflation.

[0151] In some embodiments, the inflation is pneumatic inflation.

[0152] In some embodiments, the external force is caused by flow induced pressure.

[0153] In some embodiments, the first compressive mechanical stress is uniaxial.

[0154] In some embodiments, the first compressive mechanical stress is biaxial.

[0155] In some embodiments, the first compressive mechanical stress is radial.

[0156] In some embodiments, the external force is caused by applying a stimulus to the polymer layer.

[0157] In some embodiments, the stimulus is selected from one or more of light, chemical, electromagnetic, thermal, shape memory, pressure, or mechanical stimulus. [0158] In some embodiments, the polymer includes a shape memory alloy, and the first compressive mechanical stress is caused by a shape change of the shape memory alloy.

[0159] In some embodiments, the method further includes applying a second external force to the polymer such that the stable overlayer is absorbed by the polymer layer.

[0160] In some embodiments, the second external force causes the polymer layer to be under a second compressive mechanical stress that is insufficient to cause the lubricating liquid to form a stable overlayer.

[0161] In some embodiments, the second external force causes the polymer layer to be under tension. [0162] In some embodiments, the second external force causes the polymer layer to be under no stress.

[0163] In some embodiments, the lubricating liquid includes one or more of silicone oils, siloxanes, silicate esters, mineral oils, hydrocarbons, halogenated hydrocarbons liquid, polyalphaolefins, perfluorocarbons, polyfluoroalkyl ethers, polyolefins, esters with long alkyl chains, polyalkylene glycols, or polyphenyl ethers, perfluorinated liquids, and partially fluorinated liquids.

[0164] In some embodiments, the lubricating liquid includes one or more of alkanes, olefins, saturated alkanes, and unsaturated olefins.

[0165] In some embodiments, the lubricating liquid includes one or more of halogenated alkanes, halogenated olefins, and halogenated aromatic compounds.

[0166] In some embodiments, the lubricating liquid includes one or more of fluorocarbons, perfluorocarbons, hydrofluorocarbons, hydrofluorocarbon-oligomers, compounds having partially fluorinated ponytails, partially fluorinated oils, partially fluorinated greases, fluorosilicones, tertiary perfluoroalkylamines (such as perfluorotri-n- pentylamine, FC-70, perfluorotri-n-butylamine FC-40, etc. ), perfluoroalkylsulfides and perfluoroalkylsulfoxides, perfluoroalkylethers, perfluorocycloethers (like FC-77) and perfluoropolyethers (such as KRYTOX family of lubricants by DuPont), perfluoroalkylphosphines and perfluoroalkylphosphineoxides, perfluorohexyl-octane, perfluorohexyl-ethane, perfluorobutyl-butane, perflurophenanthren, perfluorooctane, perfluorophenathrene, and their analogues, homologues, oligomers, polymers.

[0167] In some embodiments, the polymer layer includes one or more of silicone rubber, fluorosilicone, polydimethylsiloxane, vinyl methyl silicone, polyurethane, natural and synthetic polyisoprenes, polyethylene, polybutadiene, nitrile rubber, polyacrylic rubber, ethylene propylene rubber (EPM, EPDM), neoprene rubber, perfluoroelastomers, polyether block amides (PEBA), chlorosulfonated polyethylene, ethylene-vinyl acetate, polyether urethane, perfluorocarbon rubber, fluorinated hydrocarbon.

[0168] In some embodiments, the polymer includes carbon black, titanium oxide, silica, alumina, nanoparticles, or a combination thereof.

[0169] In some embodiments, the polymer layer includes a porous polymer layer.

[0170] Any one of the embodiments disclosed herein may be properly combined with any other embodiment disclosed herein. The combination of any one of the embodiments disclosed herein with any other embodiments disclosed herein is expressly contemplated. BRIEF DESCRIPTION OF THE DRAWINGS

[0171] The objects and advantages will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:

[0172] FIG. 1 A shows a schematic of the fabrication processes for a post-cure lubricating liquid infusion coating (i.e., i-polymer), according to certain embodiments.

[0173] FIG. IB shows a schematic of the fabrication processes for a pre-cure lubricating liquid addition (one-pot) coating (i.e., o-polymer), according to certain embodiments.

[0174] FIG. 2A shows a polymer layer incorporating lubricating liquid under no mechanical stress, according to certain embodiments.

[0175] FIG. 2B shows a polymer layer incorporating lubricating liquid under a compressive stress, according to certain embodiments.

[0176] FIG. 3 A shows a schematic of the structure of a polymer, according to certain embodiments.

[0177] FIG. 3B shows a schematic of the structure of a polymer formed by post-cure lubricating liquid infusion (i.e., i-polymer), according to certain embodiments.

[0178] FIG. 3C shows a schematic of the structure of a polymer formed by pre-cure addition of lubricating liquid (one-pot), according to certain embodiments.

[0179] FIG. 3D shows theoretical chemical potential of oil of i-PDMS and o-PDMS as a function of the swelling ratio, according to certain embodiments.

[0180] FIG. 3E shows the theoretical chemical potential of o-PDMS as a function of uniaxial or biaxial stretch relative to unswollen dimensions, according to certain embodiments.

[0181] FIGS. 4A-4D show a method of forming a lubricating liquid overlayer over a polymer layer using a substrate under tension, according to certain embodiments.

[0182] FIG. 5 A shows a graph of the shear modulus of i-PDMS (white bar) and o-PDMS (gray bar), according to certain embodiments.

[0183] FIG. 5B shows detection of a lubricating liquid overlayer on i-PDMS by atomic force microscopy (AFM), according to certain embodiments.

[0184] FIG. 5C shows detection of a lubricating liquid overlayer on o-PDMS by atomic force microscopy, according to certain embodiments. [0185] FIG. 6A shows anti-adhesion performance of o-PDMS, i-PDMS, Intersleek 700 and a PDMS control coating against bacteria (Cellulophaga lytica), according to certain embodiments.

[0186] FIG. 6B shows anti-adhesion performance of o-PDMS, i-PDMS, Intersleek 700 and a PDMS control coating against microalgal diatoms (Navicula incerla). according to certain embodiments.

[0187] FIG. 6C shows anti-adhesion performance of o-PDMS, i-PDMS, Intersleek 700 and a PDMS control coating against mussels (Geukerisia demissa), according to certain embodiments.

[0188] FIG. 6D shows anti-adhesion performance of o-PDMS, i-PDMS, Intersleek 700 and a PDMS control coating against barnacles (Amphibalanus amphitrite), according to certain embodiments.

[0189] FIGS. 7A-7D show fouling coverage and composition on PDMS control (FIG.

7 A), Intersleek 700 (IS700) (FIG. 7B), o-PDMS (FIG. 7C), and i-PDMS (FIG. 7D) over a 6- month emersion period at Scituate Harbor, MA, according to certain embodiments.

[0190] FIG. 8 shows representative images of the treated panels showing the fouling trends observed on each coating (PDMS, IS700, o-PDMS and i-PDMS) over time, according to certain embodiments.

[0191] FIG. 9A shows mussel spat densities on PDMS, IS700, o-PDMS and i-PDMS treatments in week 8, according to certain embodiments.

[0192] FIG. 9B shows representative images on the mussel spat accumulation patterns on each treatment type (PDMS, IS700, o-PDMS and i-PDMS), according to certain embodiments.

[0193] FIGS. 10A-10D show fouling trends on PDMS (FIG. 10A), IS700 (FIG. 10B), o- PDMS (FIG. 10C), and i-PDMS (FIG. 10D) in Morro Bay over a 15-month immersion period from May 2015 to September 2016, according to certain embodiments.

[0194] FIGS. 11 A-l IB show encrusting bryozoan (FIG. 11 A) and barnacle (FIG. 1 IB) adhesion strength to PDMS, IS700, o-PDMS and i-PDMS in Morro Bay, according to certain embodiments.

[0195] FIG. 12 shows barnacle adhesion strength to PDMS, IS700, o-PDMS and i-PDMS at Port Canaveral after 4- and 7-months static immersion [0196] FIGS. 13A-13D show fouling trends on PDMS (FIG. 13 A), IS700 (FIG. 13B), o- PDMS (FIG. 13C), and i-PDMS (FIG. 13D) in Singapore Harbor in a 24-month immersion period from June 2015 to May 2017, according to certain embodiments.

[0197] FIGS. 14A-14B show compression induction to induce lubricating overlayer formation in o-PDMS: o-PDMS samples in stress-free state (FIG. 14 A), and o-PDMS under 20% compressive strain (FIG. 14B), according to certain embodiments.

[0198] FIGS. 15A-15D show wetting behavior of compressed o-PDMS: initial water droplet (FIG. 15 A), droplet pulled along the o-PDMS once (FIG. 15B), and droplet pulled along surface a second time (FIG. 15C, FIG. 15D showing image using different lighting), according to certain embodiments.

[0199] FIGS. 16A-16C show wetting behavior of stress-free o-PDMS using water droplet interaction analysis: initial water droplet (FIG. 16A), droplet pulled along the o-PDMS once (FIG. 16B), and droplet pulled along surface a second time (FIG. 16C), according to certain embodiments.

[0200] FIGS. 17A-17D show wetting behavior of o-PDMS under 30% compressive strain over time: compressed o-PDMS after 5 days of continuous compression (FIG. 17A), control free-stress o-PDMS after 5 days (FIG. 17C), compressed o-PDMS after 10 days of continuous compression (FIG. 17B), and a control free-stress o-PDMS after 10 days (FIG. 17D), according to certain embodiments.

DETAILED DESCRIPTION

[0201] Disclosed herein are slippery surfaces formed by combining lubricating liquids and polymers such that the lubricating liquids are dispersed within the polymer network at a liquid concentration that allows formation of a stable overlayer of lubricating liquid on a surface of the polymers. In some embodiments, the materials disclosed herein form a lubricating liquid overlayer upon application of a stress. In some embodiments, formation of a stable overlayer provides non-fouling properties that can be maintained over time. In some embodiments, formation of a stable overlayer provides low-friction properties that can be maintained over time. In some embodiments, the formation of the lubricating liquid overlayer can be controlled or induced by application of stress to the polymer network. In some embodiments, slippery surfaces can be turned on or off by controlling formation of a lubricating liquid overlayer by application of stress. [0202] Disclosed herein is an article including a polymer layer under an external force causing the polymer layer to be under a first compressive mechanical stress; and a lubricating liquid within the polymer layer, the lubricating liquid being at a concentration within the polymer layer such that the lubricating liquid forms a stable overlayer over the surface of the polymer layer when the polymer layer is under the external force and the lubricating liquid does not form the stable overlayer over the surface of the polymer layer when the polymer layer is not under compressive stress.

[0203] In some embodiments, the materials disclosed herein can be formed by pre-cure addition of lubricating liquid to polymer precursors. In some embodiments, pre-cure addition lubricating liquid results in a stress-free polymer with lubricating liquid dispersed within the polymer matrix. In some embodiments, the lubricating liquid dispersed within the polymer does not form an overlayer in this stress-free state. In some embodiments, application of a stress or external force increases the chemical potential of the lubricating liquid dispersed within the polymer, causing formation of a lubricating liquid overlayer.

[0204] In some embodiments, the lubricating liquid forms a stable layer over a surface of a polymer. In some embodiments, the chemical affinity of the polymer and lubricating liquid is such that the lubricating liquid stably wets and adheres to the polymer surface. In some embodiments, the lubricating liquid overlayer is stabilized over the polymer surface by van der Waals, capillary forces, or combination thereof.

[0205] The lubricating overlayer, or slippery surface, of the present disclosure is extremely smooth, which creates a defect-free surface that can reduce contact angle hysteresis and adhesion of external matter. In some embodiments, the lubricating overlayer exhibits anti-adhesive, drag reduction, and anti-fouling properties. In some embodiments, the slippery surfaces of the present disclosure can prevent adhesion of a wide range of materials. Exemplary materials that do not stick onto the surface include liquids, liquid mixtures, complex fluids, microorganisms, solids, and gases (or vapors). For example, liquids such as water, oil-based paints, hydrocarbons and their mixtures, organic solvents, complex fluids such as crude oil, liquids containing complex biological molecules (such as proteins, sugars, lipids, etc.) or biological cells and the like can be repelled. In some embodiments, lubricating liquids can be both pure liquids and complex fluids. In some embodiments, the polymers disclosed herein can be designed to be omniphobic, hydrophobic and/or oleophobic/hydrophilic. As another example, biological materials, such as biological molecules (e.g., proteins, polysaccharides, and the like), biological fluids (e.g., urine, blood, saliva, secretions, and the like), biological cells, tissues and entire organisms such as bacteria, protozoa, spores, algae, insects, small animals, viruses, fungi, and the like can be repelled by the lubricating layer. As another example, solids like ice, frost, paper, sticky notes, glues or inorganic particle-containing paints, sand, dust particles, food items, common household contaminants, and the like can be repelled or easily cleaned from the lubricating layer.

[0206] In some embodiments, the materials disclosed herein include a polymer (e.g., such as a rubber or elastomer) that includes a dispersed lubricating liquid having a chemical affinity for that polymer material. In some embodiments the polymer is crosslinked. In some embodiments, the chemical affinity creates a solvent effect that causes the polymer to absorb an amount of the liquid. In some embodiments, the liquid absorbing effects noted herein are distinguished from capillary action of liquids in nano- and microporous media in that the interaction is on a molecular level. For example, the lubricating liquid interacts with the polymer due to intermolecular interactions such as solvation. In some embodiments, to disperse lubricating liquid within the polymer, the enthalpy of mixing between the polymer and the lubricating liquid is sufficiently low so that they mix readily with each other when mixed together, and/or undergo energetically favorable chemical interactions between each other. In comparison, capillary effects are driven by the surface energy considerations at the interface of a solid and a liquid, resulting in wicking of the liquid into well-defined preexisting microscopic channels without swelling of the underlying solid.

[0207] In some embodiments, dispersed lubricating liquid in the polymer can act as a reservoir for formation of a lubricating liquid overlayer at the surface of the polymer. Therefore, after formation of a lubricating liquid overlayer, such materials can maintain a lubricating liquid overlayer at the surface of the polymer. In some embodiments, the polymer is porous. In some embodiments, pores of the polymer can be used as reservoirs for the lubricating liquid.

[0208] In some embodiments, by selecting combinations of the lubricating liquid, polymer, and applied force, the materials disclosed herein can provide self-replenishing, nonsticking, and controllable slippery behavior towards a broad range of fluids and solids, such as aqueous liquids, cells, bodily fluids, microorganisms and solid particles such as ice. For example, due to the reservoir effect of the polymer, the coated articles can exhibit a slippery surface for extended time periods, without the need for replenishing the lubricating liquid. [0209] FIGS. 1 A-1B shows two exemplary methods of forming a polymer that includes a lubricating liquid dispersed within the polymer. Materials that include polymers and lubricating liquid dispersed within the polymer can be formed by infusing a cured polymer with lubricating liquid or by pre-cure addition of lubricating liquid to polymer precursors. In some embodiments, the method of forming a polymer with dispersed lubricating liquid results in materials with different properties, including different mechanical properties and differences in the ability to form and maintain a lubricating overlayer.

[0210] As shown in FIG. 1 A, in some embodiments, a lubricating liquid can be infused into the polymer post-cure to produce a polymer that is referred to herein as an “i-polymer.” FIG. 1 A shows general steps of preparing an i-polymer. In the non-limiting example shown in FIG. 1 A, the polymer is polydimethylsiloxane (PDMS) and the lubricating liquid is silicone oil. However, this method can be applied to any combination of polymer and lubricating liquid having a chemical affinity. As shown in FIG. 1 A, the i-polymer coating is prepared by curing the polymer, followed by infusing with a lubricating liquid in a simple post-cure infusion procedure. In some embodiments, an i-polymer coating is prepared employing following steps: curing the prepolymers or monomers of the polymer, and then immersing the cured polymer in a lubricating liquid bath and allowing the polymer and lubricating liquid to come to equilibrium. In the non-limiting example, shown in FIG. 1 A, this process can result in 45-50 wt% of silicone uptake within the cured PDMS polymer.

[0211] In some embodiments, the i-polymer is porous. In some embodiments, the lubricating liquid infused within the i-polymer exerts a swelling force on the i-polymer network. In some embodiments, the lubricating liquid infused within the i-polymer expands or swells the i-polymer network, exerting a stress on the i-polymer network. In some embodiments, an i-polymer is prepared by infusing silicone oil into an elastomeric matrix. [0212] In some embodiments, a cross-linked i-polymer is capable of increasing its volume up to several folds by absorbing large amounts of infused lubricating liquid or oil. In some embodiments, a swollen polymer network is held together by molecular strands that are connected by chemical bonds (cross-links). In some embodiments, a cross-linked polymer is capable of increasing its volume several folds by absorbing large amounts of lubricating liquids. The liquid absorbing effects noted herein are distinguished from capillary action of liquids in nano- and microporous media in that the interaction is on a molecular level.

[0213] As shown in FIG. IB, in some embodiments, a lubricating liquid is added before curing prepolymers or monomers of the polymer in a process referred to as “one-pot” approach to produce a polymer referred to as a “o-polymer.” FIG. IB shows general steps of preparing an o-polymer. In the non-limiting example shown in FIG. IB, the polymer is PDMS elastomer, and the lubricating liquid is a silicone oil. However, this method can be applied to any combination of polymer and lubricating liquid disclosed herein. As shown in FIG. IB, a polymer coating is prepared by employing the one-pot approach by adding a lubricating liquid to the uncured polymer (e.g., prepolymer or polymer precursors such as monomers) and then curing the mixture. In the non-limiting example shown in FIG. IB, approximately 50 weight percentage (wt%) of a compatible silicone oil is added to the uncured PDMS to produce the o-PDMS.

[0214] In some embodiments, one-pot approach includes adding a portion of miscible but unbound lubricating liquid to the precursor mixture containing prepolymers or monomers. In some embodiments, after curing, the lubricating liquid is chemically unbound to the polymer matrix. In some embodiments, the lubricating liquid within the o-polymer does not exert a stress on the o-polymer network. In some embodiments, the lubricating liquid within the o- polymer does not exert a swelling force on the o-polymer network. In some embodiments, the o-polymer is in a stress-free state after curing. In some embodiments, the lubricating liquid is dispersed within the o-polymer.

[0215] In some embodiments, the one-pot approach can further improve longevity of slipperiness and anti-fouling function of the polymer surface. In some embodiments, when cured, the added unbound lubricating liquid molecules in the precursor mixture reside between the crosslinked polymer network providing additional lubricity and easy chain rotations. This results in faster swelling and increased swelling ratio than pure cross-linked polymer network without added lubricating liquid. This also allows for further intake of lubricating liquid molecules during swelling, potentially leading to increased longevity of slippery and non-fouling functions.

[0216] In some embodiments, an i-polymer with an equilibrium concentration of lubricating liquid will form a lubricating liquid overlayer. In some embodiments, it has been observed that an o-polymer with the same concentration of lubricating liquid as an i-polymer at equilibrium will not form an overlayer of lubricating liquid, even though the i-polymer having the same concentration of lubricating liquid will form an overlayer of lubricating liquid. However, it was surprisingly found that, in some embodiments, when such o-polymer is subject to an external force, causing a stress within the o-polymer, the o-polymer will form an overlayer of the lubricating liquid.

[0217] FIGS. 2A-2B show an example of applying an external force to an o-polymer to form a lubricating liquid overlayer. In the example shown in FIG. 2A, an o-polymer 200 includes a lubricating liquid 202 dispersed within a polymer matrix 201. When o-polymer 200 is free of any mechanical stress, as shown in FIG. 2A, no overlayer of lubricating liquid is formed. In some embodiments, the concentration of lubricating liquid 202 within the polymer matrix 201 is such that it does not allow formation of an overlayer of lubricating liquid when the o-polymer 200 is not under a compressive mechanical stress, even though the same concentration of lubricating liquid in an i-polymer would result in the formation of a lubricating liquid overlayer. In some embodiments, as shown in FIG. 2B, when the o- polymer 200 is subject to a sufficient external force or experiences a sufficient mechanical stress, a lubricating liquid overlayer 203 can be formed.

[0218] In some embodiments, shown in FIG. 2B, o-polymer 200 is under an external force that causes the o-polymer 200 to have a compressive mechanical stress. In such embodiments, the concentration of lubricating liquid 202 within the polymer matrix 201 is such that lubricating liquid 202 forms a stable overlayer 203 over the surface of the o- polymer 200 when a sufficient external force is applied (FIG. 2B) and lubricating liquid 202 does not form stable overlayer 203 over the surface of the o-polymer 200 when the o-polymer 200 is not under a stress (e.g., when not under the external force) (FIG. 2A).

[0219] In some embodiments, by applying an external force or stress to an o-polymer, it is possible to achieve beneficial properties of an i-polymer (e.g., formation of a lubricating liquid overlayer) while also obtaining benefits of the one-pot process, including shorter processing times and use of a smaller amount of material. For example, infusing a polymer with lubricating liquid includes placing a polymer in a volume of lubricating liquid and waiting until the system reaches equilibrium. In contrast, a one-pot method can form a polymer with dispersed lubricating liquid in less time and using a smaller volume of lubricating liquid.

[0220] In some embodiments, an o-polymer with dispersed lubricating liquid that does not form a lubricating liquid overlayer in a stress-free state can be used for on-demand formation of a lubricating liquid overlayer, for example, by applying a sufficient external force to the o-polymer. In some embodiments, in an inactivated state (e.g., stress free or under a stress insufficient to form lubricating liquid overlayer), an o-polymer will not form a lubricating liquid overlayer. In some embodiments, an inactivated o-polymer provides easy handling, packaging, and transportation because of lack of a “slippery” overlayer of lubricating liquid. In some embodiments, such o-polymer is easier to cut and machine in comparison to corresponding i-polymer because of a lack of the slippery overlayer. In some embodiments, such o-polymer films can be easily die-cut/stamped into desired dimensions and the film can then be attached to final product using adhesive. In some embodiments, such o-polymer is easier to handle for installation because of a lack of slippery overlayer of lubricating liquid. In some embodiments, such o-polymer is easy to handle and work with because of a lack of slippery overlayer of lubricating liquid in comparison to the i-polymer having the same concentration of lubricating liquid but having the slippery overlayer.

[0221] In some embodiments, one-pot formulation of medical-grade silicone polymer and lubricating liquid is coated onto a pre-stretched substrate (i.e. polyurethane, rubber, textiles). In some embodiments, once stress is released from the pre-stretched substrate, lubricating liquid migrates to the surface to form a stable repellant overlayer.

[0222] In some embodiments, such o-polymer can be used for providing on-demand release of lubricating liquid overlayer by applying the external force when desired. In some embodiments, the lubricating liquid within on-demand o-polymer lasts longer because the overlayer is formed only when needed, in contrast to a corresponding i-polymer of the same lubricating liquid concentration, in which the lubricating liquid overlayer is always present and therefore may be exposed to damage and loss from external forces. In some embodiments, the lubricating liquid dispersed within the o-polymer exhibits improved shelflife because the lubricating liquid is stored within the o-polymer network. In some embodiments, the overlayer of the lubricating liquid forms on the surface only when needed, thereby limiting the exposure of the lubricating liquid to the elements of nature only when in use.

[0223] In some embodiments, for the same number of polymerizable monomers and crosslinking molecules, the o-polymer exhibits lower crosslinking density than the i-polymer. In some embodiments, the lower crosslinking density in the o-polymer than in the i-polymer is attributed to some crosslinking molecules in the o-polymer causing joining of two parts of the same monomer chain rather than two different monomer chains. In some embodiments, this results in the o-polymer exhibiting lower elastic properties than the i-polymer.

A. Framework for Controlling Formation of a Lubricating Liquid Overlayer

[0224] Disclosed herein is a framework for controlling formation of a lubricating liquid overlayer. In some embodiments, the framework disclosed herein can be used to design materials capable of forming a lubricating liquid overlayer over a polymer surface. In some embodiments, the framework disclosed herein can be used to tune the chemical potential of lubricating liquids dispersed within the polymer based on the properties of the polymer, the properties of the lubricating liquid, and forces applied to the polymer. In some embodiments, the framework disclosed herein can be used to design one-pot polymers (o-polymers) capable of forming a lubricating liquid overlayer. In some embodiments, the framework disclosed herein can be used to design one-pot polymers (o-polymers) capable of forming a lubricating liquid overlayer by applying an external force or causing a stress within the polymer.

1. Applying Flory-Rehner theory to polymer gel swelling:

[0225] A mechanistic model, based on the Flory-Rehner theory of swelling a polymer (e.g., an elastomer network) in a small molecule solvent (e.g., a lubricating liquid), explains the effects of processing parameters on the divergent properties of o-polymer and i-polymer. The model can be applied to two polymerization conditions, both with the same number of polymerizable monomers, m, and crosslinking molecules, but one with some concentration of lubricating liquid that acts as an inert diluent in the polymer.

[0226] Flory and Rehner formulate the free energy of the swelling polymer as including a stretch term and a mixing term:

[0227] Assuming molecular incompressibility of an isotropically free-swelling gel: where A is the stretch compared to the dry polymer reference state, C is the nominal concentration of lubricating liquid inside of the polymer (the number of lubricating liquid molecules divided by the dry state volume), and v is the volume per lubricating liquid molecule. The swelling ratio can be defined as J= fr. When there are no applied forces on the polymer, then the change in the free energy density W upon swelling comes only from a change in the concentration of lubricating liquid in the polymer, meaning: where « is the chemical potential of the lubricating liquid bath.

[0228] Rearranging slightly, [0229] Flory and Rehner derived an expression for W (J) for a swollen polymer network using the Gaussian chain model and the Flory-Huggins theory of mixing: where the only two parameters are N, the number of network chains per unit volume, and /, the Flory-Huggins interaction parameter. T is temperature and R is the gas constant. Differentiating with respect to J

[0230] In an i-polymer system at equilibrium, the chemical potential will be equal everywhere, and for a pure lubricating liquid the chemical potential of lubricating liquid is zero, so p = 0. The equilibrium swelling ratio Jean be measured directly, while N can be calculated from the measured shear modulus.

[0231] For the purpose of illustration of the mechanistic model and properties of the polymer system, a non-limiting example of PDMS elastomer (polymer) and silicone oil (lubricating liquid) as a polymer system is presented here. For example, for the 10: 1 ratio PDMS used in this study, Sotiri et al. found a number average molecular weight between crosslinks of 3.7 kg mol ^-1 , which for a PDMS density of 0.965 kg L ^-1 corresponds to N = 0.26 mol L ^-1 . For the 10 cSt silicone oil used in the PDMS, it provides a density of 0.935 kg L ^-1 and a molecular weight of 1250 g mol ^-1 , which corresponds to v = 1.34 L mol ^-1 .

[0232] FIGS. 3A-3C show a schematic of the polymer networks modeled in this nonlimiting example. In FIGS. 3A-3C, the black lines represent polymer chains of the polymer network 301 and dots indicate crosslinks 305. FIG. 3A shows a polymer network 301 before addition of a lubricating liquid. FIG. 3B shows a polymer network formed by infusion (i- polymer). FIG. 3C shows a polymer network formed by a one-pot method (o-polymer). The arrows in FIG. 3C indicate formation of ineffective crosslinks.

[0233] According to the model, upon complete polymerization in o-polymer system, the molar concentration of crosslinker molecules in the diluted system (o-polymer, FIG. 3C) is calculated to be clearly lower than in the non-diluted system (polymer without lubricating liquid, FIG. 3 A). This lower crosslinking density corresponds to a larger average distance between two crosslinks, leading in turn to a larger average number of monomers Nc between crosslinks. Yet, due to the conservation of mass it must be true that m = (NcV)/2. Thus, it is impossible for Nc to be higher in the diluted case if v and m are the same. This paradox can be resolved by a true number of effective crosslinks v _e < v. The total number of crosslinking molecules can still be incorporated into the network through the creation of loops, in which a crosslinker unites two parts of the same chain rather than two different chains (arrows in FIG. 3C). These ineffective crosslinks do not contribute to the mechanical network structure, as they are essentially equivalent to a shorter single chain. Thus, compared to an i-polymer (FIG. 3B), an o-polymer will have a smaller number of effective crosslinks that contribute to the network structure.

[0234] As a result, according to this model, an o-polymer is predicted to have a significantly lower elastic modulus than an i-polymer of the exact same final composition, in agreement with the observed values of shear modulus for the non-limiting example of i- PDMS infused with silicone oil (FIG. 5 A). The N of o-polymer can be determined by noting that G ~ N. Thus, for the example of PDMS with silicone oil, NOPDMS = NiPDMsGoPDMs/GiPDMS. Using the measured shear moduli of o-PDMS and i-PDMS (FIG. 5A), NOPDMS 0. 11 mol L ^-1 . These measurements then allow one to solve for/, and for T= 298 K and the swelling ratio of J= 1.7. for free-swelling bulk gels, that/ 0.61, which is reasonably close to the measured value of % = 0.743 for hexamethyldisiloxane-swollen PDMS.

[0235] In some embodiments, the mechanistic model described herein can be used to calculate the chemical potential of polymers (including i-polymers and o-polymers) under different conditions. FIGS. 3D-3E show a non-limiting example of the calculated chemical potential of silicone oil in PDMS.

[0236] FIG. 3D shows the calculated chemical potential of the silicone oil in o-PDMS and i-PDMS as a function of the swelling ratio using this model and the measured values above. The dashed black line indicates the equilibrium swelling ratio of i-PDMS and the equivalent composition of the as-prepared o-PDMS. The o-PDMS has a large negative value for the chemical potential at this composition, indicating the much higher energy cost of removing oil from the PDMS matrix compared to swollen i-PDMS. From this, it can be calculated that i-PDMS would need to lose ~ 20% of its initial oil content in order to have a chemical potential equivalent to as-prepared o-PDMS.

2. Lubricating liquid overlayer formation in i-polymer vs. o-polymer: [0237] In some embodiments, the mechanistic model described herein can be used to identify conditions under which a lubricating liquid overlayer will form. For example, the mechanistic model described herein can be used to calculate the chemical potential of a lubricating liquid in a polymer.

[0238] A non-limiting example of a PDMS system is presented here for the purpose of explaining liquid overlayer formation. The peeling of intact biofilms from an i-PDMS upon slow removal from water and the decrease of contact angle hysteresis of water on oilcontaining PDMS, strongly suggest the formation of an oil-rich region or lubricating liquid overlayer (LOL) on the surface of the PDMS when in contact with water. The formation of such a layer is in line with experimental and theoretical work showing the preferential segregation of oligomers at the surface of an elastic matrix. The driving force for this separation is the preferable interaction of the smaller oligomers with the external environment, which may be energetically driven or driven by the entropic attraction of chain ends to the surface. Dynamic contact angle hysteresis measurements can be used to estimate the change in interfacial energy due to dynamic surface lubrication of the water-PDMS interface. Spontaneous lubrication reduces the interfacial energy by about 11.5 mJ m ^-2 , providing an estimation for the driving force of creating a LOL at the water-PDMS interface. [0239] In a polymer that includes lubricating liquid dispersed within the polymer matrix, the chemical potential (p) of the lubricating liquid is the energy cost to remove lubricating liquid from the polymer and move it to an overlayer. When the chemical potential is negative, lubricating liquid will remain within the polymer. When the chemical potential is zero, there is no cost to move lubricating liquid from the bulk of the polymer to the overlayer, and lubricating liquid can be removed from the bulk of the polymer to form or maintain an overlayer.

[0240] In some embodiments, the free energy cost of removing lubricating liquid from a polymer matrix and confining it to lubricating liquid region or layer at the interface will be approximately equal to the chemical potential of the lubricating liquid in the polymer, p. If this cost is comparable to the free energy gain from creating a lubricating liquid overlayer, then it may inhibit the overlayer’s formation. In a saturated i-polymer, u 0 J/mol, providing no barrier to LOL formation. However, in some embodiments, for o-polymer, « < 0 (e.g., u -100 J/mol for o-PDMS), which means that there is an energy cost to remove a portion of the lubricating liquid from the polymer to form a lubricating liquid overlayer. For example, for o-PDMS, the energy cost to remove a 10 nm layer of silicone oil from the o- PDMS matrix is on the order of 1 mJ m ^-2 , and 10 mJ m ^-2 for a 100 nm layer. In some embodiments, the energy costs to remove lubricating liquid from the polymer are comparable to the estimated driving force for lubricating liquid overlayer formation, suggesting that lubricating liquid overlayer formation could be greatly inhibited in o-polymer compared to i- polymer.

3. Chemical potential of lubricating liquid in o-polymer under applied stress

[0241] In some embodiments, the mechanistic model described herein can be used to determine the effect of applied stress on lubricating liquid overlayer formation. For example, the mechanistic model described herein can be used to calculate the chemical potential of a lubricating liquid in a polymer under stress. For example, the mechanistic model described herein can be used to calculate the stress at which a lubricating liquid overlayer would form. [0242] If there is an external mechanical stress on the polymer, the chemical potential of the lubricating liquid in the polymer can be described by the following equations, where Gn and Xn are the mechanical stress and strain, respectively, and n = 1, 2, 3 represents cartesian coordinate directions:

[0243], Using these equations, one can solve for the chemical potential of the lubricating liquid in an o-polymer under uniaxial (oi = G, G2 = G3 = 0) and biaxial (01 = G2 = G, G3 = 0) stress. A non-limiting example of PDMS system is presented here for the purpose of explaining liquid overlayer formation. FIG. 3E shows the calculated chemical potential of o- PDMS as a function of uniaxial or biaxial stretch relative to its unswollen dimension. In this example, the as-prepared stretch of 1.19 corresponds to the zero-stress state with a negative chemical potential. In this example, compressive stress quickly raises the chemical potential, removing the barrier to form a full lubricating liquid overlayer. As shown in FIG. 3E, for both biaxial and uniaxial stretch, compression leads to an increase in the chemical potential. In some embodiments, biaxial compression of a polymer coating can be achieved without difficulty. For example a polymer can be adhered to a prestretched surface that is relaxed after curing, for example, as is done for dielectric elastomer actuators.

4. Applying the theoretical framework for formation of a lubricating liquid overlayer

[0244] In some embodiments, the mechanistic model describing one pot polymers (o- polymers) and infused polymers (i-polymers) based on the Flory-Rehner theory of swelling an elastomer network in a small molecule solvent provides an explanation for the different performance of these materials and a framework to design one pot polymers that perform similarly to infused polymers (e.g., by forming a lubricating liquid overlayer). The model suggests that for the two polymerization conditions, both with the same number of polymerizable monomers m and crosslinking molecules v, o-polymers necessarily have a smaller value of N due to the lower density of effective crosslinks, which leads to longer chains and thus fewer chains per volume. As a result, in some embodiments, o-polymers with the same composition will have significantly lower elastic modulus than i-polymers, due to the linear relationship between shear modulus and crosslinking density.

[0245] The theoretical framework described above addresses the question of why o- polymer coatings in stress-free state do not form a lubricating liquid overlayer when they have the same concentration of lubricating liquid as i-polymer. According to Flory-Rehner theory of elastomer swelling, the free energy decrease due to infiltration of lubricating liquid into a polymer matrix is counteracted by the free energy cost of stretching the polymer chains. Thus, in o-polymers, where the polymer is polymerized in a stress-free state, more lubricating liquid can be incorporated after polymerization and before reaching saturation, while the infusion process leads to complete saturation of i-polymers. The corresponding energy cost to remove lubricating liquid from the polymer matrix, the chemical potential p, is thus essentially zero in i-polymer, leading to the facile formation of a lubricating liquid overlayer when under no external force, while in o-polymers, p is high enough to maintain the lubricating liquid in the bulk of the polymer and inhibit its travel to the interface or surface to form a lubricating layer (FIG. 3D). In some embodiments, the long-term performance of i-polymer, therefore, can be determined by its ability to form and retain a lubricating liquid. The thermodynamic estimations provided above indicate that an i-polymer would need to lose a portion of its lubricating liquid loading (e.g., 20% of its lubricating liquid loading in the non-limiting example of PDMS loaded with silicon oil) to have a p value comparable to o-polymer. While fouling release events and shear stresses may remove some lubricating liquid from the surface, this lubricating liquid can be quickly replenished and total losses do not approach this threshold.

[0246] In some embodiments, the identification of a critical p value for the formation of a lubricating liquid overlayer can be used to assess the longevity of the i-polymer holistically and to guide the optimal design of coatings, including formation of a lubricating liquid overlayer on o-polymers. The theoretical framework (e.g., Flory-Rehner theory) indicates that, in some embodiments, the p of o-polymers can be reduced to zero through the application of a compressive stress during or after polymerization, providing a way to create controllable, on-demand coatings using the simpler o-polymer process. In some embodiments, this can allow for the application of o-polymers as slippery coatings with tunable wettability.

[0247] The theoretical framework described above provides guidance for the design and optimization of o-polymers that include a lubricating liquid within the polymer. For example, as shown in FIG. 3D, the chemical potential increases with the swelling ratio, which is a function of lubricating liquid concentration. When the chemical potential is zero, a lubricating liquid overlayer can form over a polymer surface. As shown in FIG. 3D, at the swelling ratio (or concentration) that an i-polymer has a chemical potential of zero and would form an overlayer, an o-polymer of the same swelling ratio (or concentration) has a lower chemical potential and therefore would not form a lubricating liquid overlayer. In some embodiments, the chemical potential can be increased, enabling the formation of lubricating liquid overlayer, by increasing concentration. In another example, shown in FIG. 3E, the chemical potential can be increased, enabling the formation of lubricating liquid overlayer, by applying a compressive stress, without the need to increase concentration of lubricating liquid. FIGS. 3D-3E therefore provide two non-limiting examples of parameters that can be selected to tune the chemical potential of a polymer that incorporates a lubricating liquid and thereby control the formation of a lubricating liquid overlayer. Numerous other parameters can be modified to tune the chemical potential and formation of a lubricating liquid overlayer, and combination of these parameters can be modified to design a polymer with desired properties using the theoretical framework described herein.

[0248] In some embodiments, the chemical potential can be tuned by modifying temperature. In some embodiments, increasing temperature can increase the chemical potential. In some embodiments, chemical potential increases linearly with temperature. [0249] In some embodiments, the chemical potential can be tuned by the concentration of lubricating liquid. For example, the chemical potential increases as the concentration of lubricating liquid increases.

[0250] In some embodiments, the chemical potential can be tuned by applying a force to the polymer or causing a stress within the polymer. For example, the chemical potential can be increased by causing a compressive stress. In some embodiments, the stress is applied by an external force. In some embodiments, the stress is biaxial. In some embodiments, the stress is uniaxial. In some embodiments, the chemical potential can be decreased by stretching or applying tension to the polymer.

[0251] In some embodiments, the chemical potential can be tuned by modifying the density of crosslinks or effective crosslinks. In some embodiments, the chemical potential can be decreased by increasing the number of crosslinks. For example, in some embodiments, increasing the number of crosslinks increases the stiffness of the polymer and increases the energy cost for lubricating liquid to infiltrate the polymer, thereby reducing the cost to release the lubricating liquid to the overlayer.

[0252] In some embodiments, the chemical potential can be tuned based on the choice of polymer and lubricating liquid. In some embodiments, the chemical potential can be tuned by the molecular weight or viscosity of the lubricating liquid. In some embodiments, the chemical potential can be tuned by the solubility parameters of the lubricating liquid. In some embodiments, the chemical affinity can be tuned by the enthalpy of mixing or Flory- Huggins interaction parameter of the lubricating liquid and polymer. In some embodiments, the chemical potential can be tuned by the chemical affinity of the polymer and lubricating liquid. In some embodiments, a high chemical affinity corresponds to a low enthalpy of mixing or low interaction parameter. For example, in some embodiments, the chemical potential depends on the interfacial energies of the materials in the system, including the interfacial energy between the polymer and lubricating liquid, the interfacial energy between the polymer and medium at the polymer surface, and the interfacial energy between the lubricating liquid and the medium at the surface of the polymer. For example, a lubricating liquid can be selected to have a low interfacial energy between the lubricating liquid and polymer, relative to the interfacial energy between the polymer and the medium. In this example, forming the lubricating liquid overlayer decreases interfacial energy at the surface, and the cost of removing lubricating liquid from bulk of the polymer to the lubricating overlayer can be counteracted by the decrease in interfacial energy at the surface. For example, the chemical potential can be tuned using fully-biodegradable oils or unique polymer-oil formulations for which the chemical potential is sufficiently low, such that the free energy cost of removing oil from the polymer to the free interface to form a lubricating liquid overlayer is low.

[0253] In some embodiments, the polymer, lubricating liquid, and concentration of lubricating liquid can be selected to design a material with tunable properties. In some embodiments, the properties of such a material, including whether an overlayer is formed, can be tuned or controlled by applying a stress. For example, the polymer, lubricating liquid, and concentration of lubricating liquid can be selected to form an o-polymer that forms a lubricating liquid overlayer when the polymer is under a stress (e.g., a compressive stress) but does not form a lubricating liquid overlayer when the polymer is not under a stress. In this way, a lubricating liquid overlayer can be switched on or off by introducing a force to the polymer.

[0254] In some embodiments, the polymers disclosed herein include a lubricating liquid at a concentration such that the lubricating liquid does not form an overlayer over the polymer when the polymer is not under a compressive stress (e.g., in a stress-free state or under tension) and the lubricating liquid forms an overlayer when the polymer is under compressive stress. In some embodiments, the concentration of lubricating liquid to achieve such a polymer will be determined based on the choice of materials (e.g., on the chemical affinity of the polymer and lubricating liquid). In some embodiments, the concentration of lubricating liquid is about 10 wt% to 70 wt%. However, in some embodiments, the concentration of lubricating liquid depends on the polymer system (e.g., the combination of lubricating liquid and polymer). In some embodiments, the concentration of lubricating liquid is about 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt %, 40 wt %, 45 wt %, 50 wt %, 55 wt %, 60 wt %, 65 wt %, 70 wt % or the concentration is in any range bounded by any two values disclosed herein.

[0255] In some embodiments, the polymer disclosed herein is disposed on a substrate under tension, and the compressive stress is caused by the substrate. In some embodiments, the substrate includes a stretchable material. In some embodiments, the substrate is an elastomer. Non-limiting examples of substrates include polyurethanes, rubber, textiles, and combinations thereof.

[0256] In some embodiments, an o-polymer coating that does not form a lubricating liquid overlayer in a stress-free state but forms the lubricating liquid layer when under an external force, is beneficial because such o-polymer coating saves on overall processing time and cost of the coating compared to the i-polymer coating having the same concentration of the lubricating liquid. For example, o-polymers do not require long post-cure infusions to reach equilibrium concentration of the lubricating liquid (e.g., up to 48 hours for the i- PDMS). This saving in processing time for o-polymers also results in a lower overall processing cost for the o-polymers coating compared to the i-polymers having the same concentration of the lubricating liquid.

[0257] In some embodiments, an o-polymer coating that does not form a lubricating liquid overlayer in a stress-free state but forms the lubricating liquid layer when under an external force, is beneficial because of improved dimensional stability of an o-polymer system compared to an i-polymer system. For example, volumetric changes in an i-polymer system can result in interfacial stresses at the substrate and lead to delamination. In some embodiments, improved dimensional stability can contribute to improved adhesion.

[0258] In some embodiments, an o-polymer coating that does not form a lubricating liquid overlayer in a stress-free state but forms the lubricating liquid layer when under an external force, is beneficial because of improved adhesion properties. For example, chemical attachment of an i-polymer system to a substrate after infusion can be challenging. In some embodiments, an o-polymer can be attached to a substrate while in a state where a lubricating liquid does not form, and a force or stress can be applied to form a lubricating liquid overlayer after attachment.

[0259] In some embodiments, an o-polymer coating having a first concentration of dispersed lubricating liquid that does not form a lubricating liquid overlayer in a stress-free state but forms the lubricating liquid layer when under an external force, is beneficial over the o-polymer coating having a second, higher concentration of dispersed liquid that allows formation of lubricating liquid overlayer in a stress-free state. In some embodiments, the o- polymer coating with first concentration of the dispersed lubricating liquid uses less lubricating oil than the o-polymer coating with the second concentration of the dispersed lubricating liquid, thus improving handling and processing cost. In some embodiments, such a polymer is thinner and light.

[0260] In some embodiments, to form a lubricating liquid overlayer in a stress-free state, an o-polymer would need to absorb a much larger amount of lubricating liquid than an i- polymer. For example, according to the example in FIG. 3D, to achieve a chemical potential of zero or greater for the lubricating liquid within the PDMS that would enable formation of the lubricating overlayer, o-PDMS will have to attain a minimum swelling ratio of approximately 2.8, whereas i-PDMS has a chemical potential of zero at an equilibrium swelling ratio of approximately 1.8. Thus, such o-PDMS coating will be bulkier and more expensive to make than the corresponding i-PDMS coating with the overlayer because it contains more lubricating liquid. Instead, in some embodiments, a compression can be applied to the post-cured o-PDMS to form an overlayer. For example, an o-PDMS coating having a swelling ratio of about 1.8 (i.e., equilibrium concentration of the corresponding i- PDMS) has a chemical potential of approximately -500 J/mol as shown in FIG. 3D. As shown in FIG. 3E, applying a biaxial compressive strain of about 0.1 on such o-PDMS coating yields a free energy of approximately OJ/mol (increase of about 200 J/mol), reduce the chemical potential of the lubricating liquid to zero, allowing for formation of oil overlayer.

B. Controlling formation of a lubricating liquid overlayer by application of stress

[0261] In some embodiments, the formation of the lubricating liquid overlayer can be controlled or induced by application of stress to the polymer network. In some embodiments, slippery surfaces can be turned on or off by controlling formation of a lubricating liquid overlayer by application of stress to the polymer. In some embodiments, a compressive stress within the polymer reduces the chemical potential of the lubricating liquid within the polymer. In some embodiments, the compressive stress is sufficient to remove a portion of the lubricating liquid from the bulk of the polymer to form a stable overlayer over the surface of the polymer.

[0262] In some embodiments, a force (e.g., an external force) is applied to the polymer layer such that the polymer layer is under stress. In some embodiments, the external force applied to the polymer includes a component applied in a direction parallel with the surface of the polymer on which the lubricating liquid overlayer is formed. In some embodiments, the external force is a compressive force and the compressive stress within the polymer includes a component parallel the external force. In some embodiments, the external force is a stretching force and the compressive stress includes a component in a direction perpendicular to the external force. In some embodiments, the external force is a compressive mechanical force and polymer is under a tensile mechanical stress that includes a component in a direction perpendicular to the external force. [0263] In some embodiments, the external force is biaxial. In some embodiments, the external force is uniaxial. In some embodiments the external force is radial.

[0264] In some embodiments, the external force is caused by stretching the polymer layer. In some embodiments, the external force is caused by inflation, e.g., pneumatic inflation. In some embodiments, the external force is caused by flow induced pressure (e.g., for a polymer coated on an internal or external surface of a pipe). In some embodiments, such a pipe can be flexible and capable of expanding under internal pressure. In some embodiments, the external force is caused by pressurizing the polymer layer (e.g., by putting the polymer layer under a hydrostatic pressure). In some embodiments, the external force is applied by bending the polymer layer. For example, bending a polymer layer can introduce compressive stress in a first region of the polymer layer and tension in a second region of the polymer.

[0265] In some embodiments, an external force can be applied locally to form a lubricating liquid overlayer over a portion of the polymer. In some embodiments, an external force can be applied locally using an indenter.

[0266] In some embodiments, an external force can be applied by applying a stimulus to the polymer layer. In some embodiments, a compressive stress can be caused by applying a stimulus to the polymer layer. In these embodiments, the polymer layer includes a stimuli- responsive polymer. In same embodiments, stimuli-responsive polymers can change their shape and/or dimensions, thereby introducing a compressive stress, in response to one or more stimuli through external influences: for example, the effect of light, temperature, pressure, an electric or magnetic field, or a chemical stimulus. In some embodiments, the chemical stimulus is a cross-linking agent or a swelling agent. In some embodiments, the polymer layer includes an embedded shape memory alloy. In some embodiments, a shapememory alloy changes its shape in response to a stimuli: for example the effect of light, temperature, pressure, an electric or magnetic field, or a chemical stimulus. For example, a compressive stress can be caused by a shape change of a shape memory alloy embedded within or disposed on a polymer layer. For example, a polymer layer can be coated onto a medical device (e.g., a stent) that includes a shape memory alloy.

[0267] In some embodiments, compression can be introduced to the polymers disclosed herein during curing of the polymer layer. In some embodiments, compression can be caused by curing the polymer on a pre-stressed or pre-stretched substrate, e.g., a substrate under tension. [0268] Disclosed herein is an article including a substrate under tension; a polymer layer on the substrate; and a lubricating liquid within the polymer layer, the lubricating liquid being at a concentration within the polymer layer such that no stable overlayer is formed over a surface of the polymer layer, wherein the substrate is configured to cause a first compressive mechanical stress on the polymer layer when the tension is released, the first compressive mechanical stress being sufficient to cause the lubricating liquid to form a stable overlayer on the polymer layer.

[0269] FIGS. 4A-4D show an exemplary method of introducing compressive stress to a polymer 400 incorporating lubricating liquid 402 during curing. A shown in FIG. 4A, a substrate 404 is stretched by applying an external tension by an external force. Then, as shown in FIG. 4B, a polymer 400 can be formed on the stretched substrate 404. As shown in FIG. 4B, the polymer 400 includes a polymer matrix 401 and lubricating liquid 402 incorporated within the polymer matrix. In some embodiments, the polymer is formed by a one-pot method (e.g., by adding the lubricating liquid to polymer precursors before curing). In the example shown in FIG. 4B, a lubricating liquid overlayer does not form over the polymer while the tension is maintained because the lubricating liquid is at a concentration such that the chemical potential of the lubricating liquid is less than zero when the tension is applied.

[0270] As shown in FIG. 4C, after curing, the external force applying the external tension can be released, causing the substrate to contract. However, because of the cured polymer 400 disposed on the substrate 404, the substrate cannot contract to its original pre-stretch dimensions, resulting in a residual tension in the substate 404 and compression within the polymer matrix 401. In some embodiments, the residual tension is less than the external tension. In some embodiments, the compression in the polymer increases the chemical potential of the lubricating liquid. In the example shown in FIG. 4C, the compression in the polymer is sufficient to cause a portion of the lubricating liquid 402 to be removed from bulk of the polymer 400 and form an overlayer 403 over the surface of the polymer.

[0271] In some embodiments, after curing, the substrate can be maintained at a tension that is less than the external tension. For example, the external force applied during curing can be released such that the external tension is reduced to a lesser tension. In some embodiments, this lesser tension is selected such that the chemical potential of the lubricating liquid is less than zero and a lubricating liquid overlayer does not form over the surface of the polymer. In some embodiments, when the tension is released, the substrate contracts, resulting in a residual tension in the substrate and a compression in the polymer. In some embodiments, the compression in the polymer is sufficient to cause a portion of the lubricating liquid to be removed from the bulk of the polymer and form an overlayer over the surface of the polymer. In some embodiments, the compression in the polymer is not sufficient to cause a portion of the lubricating liquid to be removed from the bulk of the polymer and form an overlayer over the surface of the polymer. In these embodiments, an overlayer can be formed by applying an external force (e.g., additional compressive stress) to the polymer.

[0272] As shown in FIG. 4D, in some embodiments, the substrate 404 can subsequently be removed. In some embodiments, when a pre-stretched substrate is removed, the polymer will return to its original dimensions (e.g., a relaxed or stress-free state). In some embodiments, when a pre-stretched substrate is removed, the chemical potential will decrease to that of a stress-free polymer. As shown in FIG. 4D, in these embodiments, the lubricating liquid overlayer will be reabsorbed by the bulk of the polymer.

[0273] In some embodiments, the external tension is be caused by stretching the substrate in at least one direction. In some embodiments, the external tension is caused by stretching the substrate in two directions. In some embodiments, the substrate is stretched uniaxially. In some embodiments, the substrate is stretched biaxially. In some embodiments, the external tension is caused by compressing the substrate in at least one direction. In some embodiments, the external tensile force is caused by compressing the substrate in at least two directions.

[0274] In some embodiments, a substrate can have a spherical or cylindrical shape. In these embodiments, a substrate can introduce radial forces. In these embodiments, a substrate can be stretched radially by inflating the substrate. In these embodiments, the amount of stretch in the substrate can be modified by modifying the inflation pressure. In some embodiments, a substrate can be inflated to a first pressure, introducing tension in the substrate, and a polymer including dispersed lubricating liquid can be formed on the surface on the substrate while the substrate is at a first pressure. In these embodiments, a compressive stress can be caused in the polymer by changing the inflation pressure (e.g., by decreasing the inflation pressure to a second pressure). In some embodiments, the compressive stress is sufficient that a lubricating liquid overlayer forms over the polymer. In some embodiments, an external tensile force is caused by radially expanding the substrate. In some embodiments, an external tensile force is caused by radially compressing the substrate. [0275] In some embodiments, an external force can be applied by applying a stimulus to the substrate. In some embodiments, a tension in the substrate can be caused by applying a stimulus to the substrate. In these embodiments, the substrate includes a stimuli-responsive material. In same embodiments, stimuli-responsive materials can change their shape and/or dimensions, thereby introducing a compressive stress, in response to one or more stimuli through external influences: for example, the effect of light, temperature, pressure, an electric or magnetic field, or a chemical stimulus. In some embodiments, the chemical stimulus is a cross-linking agent or a swelling agent. In some embodiments, the polymer layer includes a shape memory alloy. In some embodiments, a shape-memory alloy changes its shape in response to a stimuli: for example the effect of light, temperature, pressure, an electric or magnetic field, or a chemical stimulus. For example, a compressive stress can be caused by a shape change of a shape memory alloy embedded within or disposed on a polymer layer. For example, a polymer layer can be coated onto a medical device (e.g., a stent) that includes a shape memory alloy.

C. Materials

[0276] In some embodiments, the materials disclosed herein include a polymer and a suitable lubricating liquid. In some embodiments, the appropriate polymers, lubricating liquids, and polymer and lubricating liquid combinations can be identified based on the theoretical framework described above.

[0277] In some embodiments, the polymer preferentially includes a dispersed lubricating liquid on the surface rather than a fluid, complex fluids or undesirable solids to be repelled such that the lubricating liquid overlayer, once formed, cannot be displaced by the liquid or solid to be repelled. In these embodiments, the lubricating liquid acts as a better solvent toward the underlying polymer than the liquid to be repelled. These factors can be designed to be permanent or lasting for time periods sufficient for a desired life or service time of the polymer surface or for the time till a re-application of the partially depleted infusing liquid is performed.

1. Examples of Polymer Materials

[0278] In some embodiments, the polymer is a cross-linked polymer. In some embodiments, the polymer is a gel capable of being swollen with the lubricating liquid. In some embodiments, the polymer has an affinity for the lubricating liquid. [0279] In some embodiments, the polymer material can be chosen from a wide range of rubbers and elastomers, and other polymers. In some embodiments, the polymer is compressible. In some embodiments, the polymer swells significantly in the presence of certain solvent lubricating liquids. For example, the polymer can include rubber or elastomeric polymers, which rubbers or elastomeric polymers known to swell in the presence of an appropriate solvating liquid. In some embodiments, the polymer is a nonporous material.

[0280] In some embodiments, the polymer is a covalently cross-linked polymer. In some embodiments, the polymer is a simple single polymer or complex mixture of polymers, such as polymer blends or co-polymers and the like. In some embodiments, the nature and degree of crosslinking can change the properties of the polymer. For example, cross-linking density can be used to control how much the polymer will swell (e.g., a lightly cross-linked polymer may swell more than a highly cross-linked polymer) or how much lubricating liquid can be dispersed within the polymer. In some embodiments, crosslinking density can be used to control the stiffness of the polymer matrix or the chemical potential of a lubricating liquid dispersed within the polymer. In some embodiments, the crosslinks can be physical and therefore reversible and/or readily disruptible by solvation so that the swelling ratio is large and/or the swelling rate is high. In some embodiments, the polymer is a copolymer or blend polymer or a composite material (e.g., a mixture of polymers containing nanoparticles or microscale filler materials). In some embodiments, the polymer is a copolymer of covalently and physically cross-linked blocks. In some embodiments, the polymer can be patterned into regions that would subsequently have different degrees of swelling upon addition of lubricating liquid.

[0281] In some embodiments, the polymer includes silicone rubber, fluorosilicone, polydimethylsiloxane, vinyl methyl silicone, polyurethane, natural and synthetic, polyurethane, natural and synthetic polyisoprenes, polyethylene, polybutadiene, nitrile rubber, polyacrylic rubber, ethylene propylene rubber (EPM, EPDM), neoprene rubber, perfluoroelastomers, fluoroelastomers, polyether block amides (PEBA), chlorosulfonated polyethylene, ethylene-vinyl acetate, polyether urethane, perfluorocarbon rubber, fluorinated hydrocarbon or combination thereof.

[0282] In some embodiments, the polymer includes natural and synthetic elastomers. Non-limiting examples of polymers include Ethylene Propylene Diene Monomer (EPDM, a terpolymer of ethylene, propylene and a diene component), natural and synthetic polyisoprenes such as cis-l,4-polyisoprene natural rubber (NR) and trans- 1,4-polyisoprene gutta-percha, isoprene rubber, chloroprene rubber (CR), such as polychloroprene, Neoprene, Baypren, Butyl rubber (copolymer of isobutylene and isoprene), Styrene-butadiene Rubber (copolymer of styrene and butadiene, SBR), Nitrile rubber (copolymer of butadiene and acrylonitrile, NBR), also called Buna N rubbers, Epichlorohydrin rubber (ECO), Polyacrylic rubber (ACM, ABR), Fluoroelastomers (FKM, and FEPM) Viton, Tecnoflon, Fluorel, Atlas and Dai -El, Perfluoroelastomers (FFKM) Tecnoflon PFR, Kalrez, Chemraz, Perlast, Polyether block amides (PEBA), Chlorosulfonated polyethylene (CSM), (Hypalon), Ethylene-vinyl acetate (EVA), Polybutadiene, Polyether Urethane, Perfluorocarbon Rubber, Fluorinated Hydrocarbon (Viton), silicone, fluorosilicone, polyurethane, polydimethylsiloxane, vinyl methyl silicone, and combinations thereof. In some embodiments, the polymer includes composite materials where one or more of such exemplary polymers are compounded with other filler materials such as carbon black, titanium oxide, silica, alumina, nanoparticles, and the like.

[0283] In some embodiments, the polymer is a fluoropolymer. Non-limiting examples of fluoropolymers include polytetrafluoroethylene (Teflon), polyvinylfluoride, polyvinylidene fluoride, fluorocarbon [chlorotrifluoroethylenevinylidene fluoride] (Viton, Fluorel), Fluoroelastomer [Tetrafluoroethylene-Propylene] (AFLAS), perfluorinated elastomer [perfluoroelastomer] (DAI-EL, Kalrez), tetrafluoroethylene (Chemraz), perfluoropolyether, and combinations thereof. In some embodiments, the polymer is a fluorosilicone having a PDMS backbone and some degree of fluoro-aliphatic side chains. Non-limiting examples of fluorinated groups in a fluorosilicone include trifluoropropyl, non-afluorohexylmethyl, and fluorinated ethers. In some embodiments, fluorosilicones have variable amounts of fluorosubstitution and lengths of fluorinated side groups. In some embodiments, the polymer includes fluoroalkyl side chains. Non-limiting examples of such polymers include polyfumerate, polymethacrylate, and polyacrylate with fluoroalkyl side chains. In some embodiments such fluoroalkyl side chains have 3, 5, 7, 8, 9, 10, 11, 16, or 18 carbons.

[0284] In some embodiments, the polymer includes a polyester, polyethylene terephthalate (PET), polyethylene (PE, HDPE, LDPE), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polypropylene (PP), polystyrene (PS, HIPS), polyamides (PA, Nylons), acrylonitrile butadiene styrene (ABS), poly ethylene/ Acrylonitrile Butadiene Styrene (PE/ ABS), polycarbonate (PC), polycarbonate/acrylonitrile butadiene styrene (PC/ABS), polyurethanes (PU), melamine formaldehyde (MF), phenolics (PF) or (phenol formaldehydes, polyetheretherketone (PEEK), polyetherimide (PEI), polylactic acid (PLA), polyalkyl methacrylate (like PMMA), urea-formaldehyde (UF), and combinations thereof.

2. Examples of Polymer Precursors

[0285] In some embodiments, the prepolymer or base resin is selected such that it is compatible with the lubricating liquid. Thus, in some embodiments, the prepolymer is selected to provide preferential wetting by the lubricating liquid in the cured state, and/or is selected because it is able to wet and stably adhere the lubricating liquid in the cured state. In some embodiments, the prepolymer is nonreactive but miscible with the lubricating liquid. In some embodiments, the exemplary prepolymer is stable and non-reactive with the lubricating liquid, miscible with the lubricating liquid in the prepolymer state, and miscible with the polymer such that is becomes dispersed within the polymer upon curing. In some embodiments, the exemplary prepolymer is stable and non-reactive with the lubricating liquid, miscible with the lubricating liquid in the prepolymer state, but immiscible and able to self-segregate from the lubricating liquid as it cures. Further, in some embodiments, the curing agent also desirably is chemically non-reactive or substantially non-reactive with the lubricating liquid.

[0286] In some embodiments, the polymer precursors can include precursors of perfluorinated and/or polyfluorinated polymers. For example, fluorinated alternating aryl/alkyl vinylene ether (FAVE) polymers can be prepared from addition polymerization of aryl trifluorovinyl ethers (TFVEs) with 1,4-butanediol or 4-hydroxybenzyl alcohol.

[0287] In some embodiments, polymer precursors for an o-polymer includes a monomer, a base resin, or a prepolymer. In some embodiments, the base resin or prepolymer for o- polymer can include polymerizable monomers, terminal-group functionalized oligomers or polymers, side-group functionalized oligomers or polymers, telechelic oligomers or polymers. In some embodiments, the exemplary telechelic polymers or end-functionalized polymers are macromolecules with two reactive end groups and are used as cross-linkers, chain extenders, and important building blocks for various macromolecular structures, including block and graft copolymers, star, hyperbranched or dendritic polymers. In some embodiments, telechelic polymers or oligomers can enter into further polymerization or other reactions through its reactive end-groups. An exemplary telechelic polymer is a di-end- functional polymer where both ends possess the same functionality. In some embodiments, where the chain-ends of the polymer are not of the same functionality they are termed endfunctional polymers. Exemplary telechelic polymers include polyether diols, polyester diols, polycarbonate diols, and polyalcadiene diols. Exemplary end-functionalized polymers also include polyacrylates, polymethacrylates, polyvinyls, and polystyrenes. In some embodiments, for o-polymer, the ratio of lubricating liquid to resin is as high as high as 2:1. [0288] In some embodiments, the polymer precursor can be a perfluoroalkyl or polyfluoroalkyl monomer, such as perfluoroalkyl methacrylates. In other embodiments, an initiator may be included to initiate polymerization. For example, photoinitiators, thermal initiators, a moisture-sensitive catalyst or other catalyst can be included. In some embodiments, polymerization is affected by exposure of the compositions to a suitable trigger, such as light, including ultraviolet energy, thermal energy or moisture.

[0289] In some embodiments, the prepolymer precursor includes fluorinated monomers or oligomers having some degree of unsaturation, such as (perfluorooctyl)ethyl methacrylate, or end functionalized with other reactive moi eties that can be used in the curing process. For example, in some embodiments, the monomers can be allyl based and include allyl heptafluorobutyrate, allyl heptafluoroisopropyl ether, allyl lH,lH-pentadecafluorooctyl ether, allylpentafluorobenzene, allyl perfluoroheptanoate, allyl perfluorononanoate, allyl perfluorooctanoate, allyl tetrafluoroethyl ether, and allyl trifluoroacetate. The monomers can be itacone- or maleate-based and include hexafluoroisopropyl itaconate, bis(hexafluoroisopropyl) itaconate; bis(hexafluoroisopropyl) maleate, bis(perfluorooctyl)itaconate, bis(perfluorooctyl)maleate, bis(trifluoroethyl) itaconate, bis(2,2,2-trifluoroethyl) maleate, mono-perfluorooctyl maleate, and mono-perfluorooctyl itaconate. In some embodiments, the monomer can be acrylate- and methacrylate (methacrylamide)-base and include 2-(N-butylperfluorooctanesulfamido)ethyl acrylate, lH,lH,7H-dodecafluoroheptyl acrylate, trihydroperfluoroheptyl acrylate, 1H,1H,7H- dodecafluoroheptyl methacrylate, trihydroperfluoroheptyl methacrylate, 1H,1H,11H- eicosafluoroundecyl acrylate, trihydroperfluoroundecyl acrylate, 1H,1H,11H- eicosafluoroundecyl methacrylate, trihydroperfluoroundecyl methacrylate, 2-(N- ethylperfluorooctanesulfamido)ethyl acrylate, 2-(N-ethylperfluorooctanesulfamido)ethyl methacrylate, lH,lH,2H,2H-heptadecafluorodecyl acrylate, 1H,1H,2H,2H- heptadecafluorodecyl methacrylate, lH,lH-heptafluorobutylacrylamide, 1H,1H- heptafluorobutyl acrylate, lH,lH-heptafluorobutylmethacrylamide, lH,lH-heptafluoro-n- butyl methacrylate, lH,lH,9H-hexadecafluorononyl acrylate, 1H,1H,9H- hexadecafluorononyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, 2, 2, 3, 4,4,4- hexafluorobutyl methacrylate, hexafluoroisopropyl acrylate, 1,1, 1,3, 3, 3 -hexafluoroisopropyl acrylate, lH,lH,5H-octafluoropentyl acrylate, lH,lH,5H-octafluoropentyl methacrylate, 2,2,3,3,3-pentafluoropropyl acrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, perfluorocyclohexyl methyl acrylate, perfluorocyclohexylmethyl methacrylate, perfluoroheptoxypoly(propyloxy) acrylate, perfluoroheptoxypoly(propyloxy) methacrylate, perfluorooctyl acrylate, lH,lH-perfluorooctyl acrylate, lH,lH-perfluorooctyl methacrylate and hexafluoroisopropyl methacrylate. In other embodiments, suitable monomers include pentafluorostyrene, perfluorocyclopentene, 4-vinylbenzyl hexafluoroisopropyl ether, 4- vinylbenzyl perfluorooctanoate, vinyl heptafluorobutyrate, vinyl perfluoroheptanoate, vinyl perfluorononanoate, vinyl perfluorooctanoate, vinyl trifluoroacetate, tridecafluoro- 1, 1,2,2- tetrahydrooctyl- 1,1 -methyl dimethoxy silane, tridecafluoro- 1,1,2, 2-tetrahydrooctyl-l- dimethyl methoxy silane, and cinnamate.

[0290] In some embodiments, silicone monomers can be used, such as PDMS precursor (i.e. Sylgard® 184), l,4-bis[dimethyl[2-(5-norbornen-2-yl)ethyl]silyl]benzene, 1,3- di cyclohexyl- 1,1, 3, 3-tetrakis(dimethylsilyloxy)disiloxane, 1, 3-di cyclohexyl- 1,1, 3, 3- tetrakis(dimethylvinylsilyloxy)disiloxane, 1, 3-di cyclohexyl- 1,1, 3, 3-tetrakis[(norbornen-2- yl)ethyldimethylsilyloxy]disiloxane, 1,3-divinyltetramethyldisiloxane, 1, 1, 3, 3,5,5- hexamethyl-l,5-bis[2-(5-norbomen-2-yl)ethyl]trisiloxane, silatrane glycol, 1, 1,3,3- tetramethyl-l,3-bis[2-(5-norbornen-2-yl)ethyl]disiloxane, 2,4,6,8-tetramethyl-2,4,6,8- tetravinylcyclotetrasiloxane, and N-[3-(trimethoxysilyl)propyl]-N' -(4- vinylbenzyl)ethylenediamine.

[0291] In some embodiments, polymer precursors include crosslinkers. In some embodiments, crosslinking density can be used to modify property of the resulting polymer, including stiffness, chemical potential of a lubricating liquid within the polymer, and ability of a lubricating liquid to be dispersed within a polymer.

3. Examples of Lubricating Liquids

[0292] In some embodiments, the lubricating liquid is selected such that the material to be repelled (or does not adhere) is not soluble or miscible in the lubricating liquid layer, which contributes to the low adhesion exhibited by the material to be repelled. In some embodiments, for the lubricating liquid and the environmental material to be immiscible with each other, the enthalpy of mixing between the two should be sufficiently high (e.g., water/oil; insect/oil; ice/oil, etc.) that they phase separate from each other when mixed together, and/or do not undergo substantial chemical reactions between each other. In some embodiments, the lubricating liquid and the material to repel are substantially chemically inert with each other so that they physically remain distinct phases/materials without substantial mixing between the two.

[0293] In some embodiments, a lubricating liquid can be selected to have a viscosity that provides appropriate lubricity and longevity properties. In some embodiments, the viscosity of the lubricating liquid affects the lubricating liquid secretion rate. In some embodiments, the lubricating liquid has a low viscosity. In some embodiments, a low viscosity lubricating liquid provides increased mobility and movement to the surface to rapidly form the slippery surface and to induce fast sliding of contaminants off the surface and re-lubrication of the surface layer.

[0294] In some embodiments, the lubricating liquid is selected based on the availability or desired surface properties (hydrophilicity, oleophobicity, etc.). In some embodiments, exemplary lubricating liquids include hydrophilic, hydrophobic and oleophobic liquids, such as fluorinated lubricants (liquids or oils), silicones, silicone oils, siloxanes, mineral oil, plant oil, hydrocarbons, halogenated hydrocarbons, water (or aqueous solutions including physiologically compatible solutions), ionic liquids, polyolefins, including polyalpha-olefins (PAO), esters, synthetic esters, esters with long alkyl chains, polyalkylene glycols (PAG), polyphenyl ethers, phosphate esters, alkylated naphthalenes (AN), aromatics and silicate esters and combinations thereof.. Non-limiting examples of silicones include silicon tetraethoxide, tetraethyl orthosilicate (TEOS), Vinyl-based silicones derivatives, and H — Si based silicones derivatives.

[0295] In some embodiments, the lubricating liquid is a perfluorinated liquid or partially fluorinated liquid. In some embodiments, partial fluorination leads to a stepwise reduction in specific gravity, while hydrogenation leads to augmented polarization and increased lipophilic or silicone-solvent properties. In some embodiments, the lubricating liquid includes multiple classes of partially fluorinated inert liquids, including oligomers and mixtures. The physical and chemical properties make partially fluorinated inert liquids suitable for this application, as well. A number of types and classes of such liquids are listed throughout this application and in the examples. A person skilled in the art will recognize that the list and the examples are non-limiting and there are multiple variations and permutations, not listed here, of polymer/partially fluorinated liquid that will work similarly well for the purposes of forming a lubricating liquid overlayer. Non-limiting examples of perfluorinated liquids or partially fluorinated liquids include fluorocarbons, perfluorocarbons, hydrofluorocarbons, hydrofluorocarbon-oligomers, compounds having partially fluorinated ponytails, partially fluorinated oils, partially fluorinated greases, fluorosilicones, tertiary perfluoroalkylamines (such as perfluorotri-n-pentylamine, FC-70, perfluorotri-n-butylamine FC-40, etc. ), perfluoroalkylsulfides and perfluoroalkylsulfoxides, perfluoroalkylethers, perfluorocycloethers (like FC-77) and perfluoropolyethers (such as KRYTOX family of lubricants by DuPont), perfluoroalkylphosphines and perfluoroalkylphosphineoxides, perfluorohexyl-octane, perfluorohexyl-ethane, perfluorobutyl -butane, perflurophenanthren, perfluorooctane, perfluorophenathrene, and their analogues, homologues, oligomers, polymers, mixtures, and combinations thereof. In some embodiments, perfluoroalkyls are linear or branched. In some embodiments, the lubricating liquid includes a hydrofluorocarbon oligomer. In some embodiments, hydrofluorocarbon oligomers include two to four hydrofluorocarbon molecules and have viscosity between 90 and 1750 mPas. In some embodiments, hydrofluorocarbon oligomers include a star-shaped molecular structure with polar, hydrogenated molecules at the center. In some embodiments, long-chain perfluorinated carboxylic acids (e.g., perfluorooctadecanoic acid and other homologues), fluorinated phosphonic and sulfonic acids, fluorinated silanes, and combinations thereof are used as the lubricating liquid. In some embodiments, perfluoroalkyl group in these compounds are linear or branched, and some or all linear and branched groups are only partially fluorinated.

[0296] In some embodiments, the lubricating liquid includes fluorinated oils and liquids. Non-limiting examples of partially fluorinated oils and greases include glutarate, camphorate, tricarballylate, phosphate, phosphonate, ether phospho-nitrilate, and cyanurate derivatives of partly fluorinated alcohols. Non-limiting examples of partly fluorinated alcohols include Bis(y’-amyl) 3 -methylglutarate, Bis(y'-heptyl) 3 -methylglutarate, Bis(y'-heptyl) 2- methylglutarate, Bis(y'-heptyl) d-camphorate, Bis(y'-heptyl) 2,2'-dimethyl-methylglutarate, Bis(y' -heptyl) 3, 3 -dimethyl-m ethylglutarate, Tris(y'-amyl) tricarballylate, 1, 2,4,5- Tetrakis(\|/'-amyl) pyromellitate, Tris(y'-amyl) phosphate, Tris(y' -heptyl) tricarballylate, Bis(y'-amyl) benzene-phosphate, Bis(y'-nonyloxy)-butane, Bis(y'-nonyloxy)-hexane, Bis(y'- amyl) phosphoninitrilate trimer, (y'-amyl) phosphoninitrilate trimer, and Bis(y'-amyl) (\|/- nonyl) cyanurate. In some embodiments, fluorinated liquids include esters or ester-type derivatives with partially fluorinated moieties.

[0297] In some embodiments, the lubricating liquid is a hydrocarbon. Non-limiting examples of hydrocarbons include alkanes, olefins, and their liquid higher homologues, such as oligomers and polymers. In some embodiments, the lubricating liquid is a saturated alkane, an unsaturated olefin, or one of their liquid oligomers or polymers. In some embodiments the lubricating liquid is a halogenated hydrocarbon, including halogenated alkanes, halogenated olefins and aromatic compounds.

[0298] In some embodiments, the lubricating liquid is mineral oil, which includes light mixtures of higher alkanes from a mineral source. In some embodiments the lubricating liquid is plant oil or other ester with a long alkyl chain. In some embodiments, the lubricating liquid is an organosilicone compound (e.g. silicone elastomer or silicone oil).

4. Examples of Polymer and Lubricating Liquid Combinations

[0299] In some embodiments, the lubricating liquid is matched chemically with the polymer that it is dispersed within. In some embodiments, the lubricating liquid and polymer have a chemical affinity for one another. In some embodiments, the enthalpy of mixing between the polymer and the lubricating liquid is sufficiently low so that they mix readily with each other when mixed together. In some embodiments, the Flory -Huggins interaction parameter between the polymer molecules and the lubricating liquid is sufficiently low so that they mix readily with each other when mixed together.

[0300] In some embodiments, the lubricating liquid has a high solubility or miscibility with the polymer. In some embodiments, a high solubility or miscibility increases lubricating liquid concentration that can be dispersed in the polymer. In some embodiments, a high solubility or miscibility improves excretion dynamics of the lubricating liquids. In some embodiments, a high solubility or miscibility minimizes phase separation of the lubricating liquid. In some embodiments, the lubricating liquid is capable of swelling the polymer as well. In some embodiments, the lubricating liquid is selected so that it remains within the bulk of the polymer, rather than self-secreting or sweating out of the polymer without added stress.

[0301] In some embodiments, the lubricating liquid and polymer have a chemical affinity for one another. For example, when the polymer is a hydrophobic polymer such as polydimethylsiloxane (PDMS), the lubricating liquid can be a hydrophobic liquid such as silicone oil, hydrocarbons, and/or the like. As an illustrative example, a silicone elastomer (e.g., which is covalently cross-linked) can include a dispersed silicone oil. For example, a PDMS elastomer can be used with a silicone oil (e.g., such as methyl, hydroxyl, or hydride- terminated PDMS). Hydride-terminated PDMS has been demonstrated to show good swelling and dispersion with a range of lubricating liquids. Hydroxyl-terminated silicone oil in PDMS is also another type of swellable polymer providing oleophobic/hydrophilic surface. [0302] In some embodiments, a fluorinated polymer is combined with a perfluorinated or fluorinated liquid to form a fluorogel. In some embodiments, a butyl rubber is combined with mineral oil. In other embodiments, a silicone is combined with a silicone oil.

Exemplary non-limiting combinations of polymers and lubricating liquids are shown in Table 1 below. A person skilled in the art will recognize that other combinations comprising the classes of polymers and lubricating liquids present not necessarily in the same rows in Table 1 can be used, as well. In certain embodiments, lubricating liquids can contain analogues, homologues, oligomers, polymers, and mixtures of the lubricating liquids listed in Table 1.

Table 1. Exemplary combinations of polymers and lubricating liquids.

[0303] In some embodiments, the polymer layer containing the lubricating liquid incorporates amphiphilic properties, hybrid material approaches, or active substances. In some embodiments, the lubricating liquid within the polymer layer not only improves the FR coating performance, but is also biodegradable.

5. Examples of Substrates [0304] In some embodiments, the materials described herein include a substrate, for example a substrate on which the polymer layer is disposed. In some embodiments, the substrate material includes a stretchable material. In some embodiments, the substrate includes an extensible material. In some embodiments, the substrate includes an elastomer. In some embodiments, the substrate is transparent. In some embodiments, the lubricating liquid has a low solubility in the substrate. For example, a substrate can be selected such that the lubricating liquid has a low solubility in the substrate and the substrate therefore does not uptake the lubricating liquid. In some embodiments, the substrate does not react with the lubricating liquid. In some embodiments, the substrate has good adhesion with the polymer. In some embodiments, adhesion between the polymer and substrate can be modified using adhesion promoters.

[0305] Non-limiting examples of substrates include silicone rubber, polyurethane, polyisoprene, polyethylene, polybutadiene, nitrile rubber, ethylene propylene rubber (EPM, EPDM), neoprene rubber, fluoroelastomers, or a combination thereof. In some embodiments, pre-stressed substrate is a material with a sufficiently high elongation at yield. For example, in some embodiments the pre-stressed substrate is a polymer that can be elongated by 50%- 1000%. In some embodiments, the pre-stressed substrate includes textiles/fabrics, woven mesh materials, shape memory alloy, metals, and combination thereof.

[0306] Those skilled in the art would realize that the embodiments and examples of materials disclosed above are non-limiting and that appropriate polymers, lubricating liquids, and polymer and lubricating liquid combinations can be selected and determined based on the theoretical mechanism described above.

D. Methods of Making Materials with Controllable Lubricating Liquid Overlayer

[0307] Disclosed herein is a method of making an article including: adding a lubricating liquid to one or more polymer precursors; and curing the one or more polymer precursors to form a polymer layer dispersed with the lubricating liquid, the lubricating liquid is added to the polymer precursors at a concentration such that, after forming the polymer layer the lubricating liquid does not form a stable overlayer on a surface of the polymer layer; and applying an external force to the polymer layer such that the polymer layer is under a first compressive mechanical stress sufficient to cause the lubricating liquid to form the stable overlayer on the surface of the polymer layer. [0308] In some embodiments, the polymers disclosed herein are formed by a one-pot method, e.g., by pre-cure addition of a lubricating to polymer precursors. In some embodiments, the polymer is formed by adding a lubricating liquid to one or more polymer precursors before curing, followed by curing to form a polymer layer with the lubricating liquid dispersed within the polymer. In some embodiments, a lubricating liquid can be added to polymer precursors such that the lubricating liquid can be dispersed within the polymer while curing. In some embodiments, a lubricating liquid can also be a solvent for the prepolymer composition. In some embodiments, pre-cure addition of a lubricating liquid results in a stress-free polymer with lubricating liquid dispersed within the polymer matrix. In some embodiments, the lubricating liquid dispersed within the polymer does not form an overlayer in this stress-free state. In some embodiments, an external force or stress can be applied to the polymer during or after curing to form a lubricating liquid overlayer.

[0309] In some embodiments, low molecular polymer precursors can be ‘cured’ or solidified by reaction of end-functionalized polymers with curing agents, which increases the molecular weight of the macromolecule. Exemplary curing agents include other oligomers or polymers with two or more reactive groups, or with bifunctional crosslinking agents. Exemplary telechelic polymers include polyether diols, polyester diols, polycarbonate diols, and polyalcadiene diols. Exemplary end-functionalized polymers also include polyacrylates, polymethacrylates, polyvinyls, and polystyrenes.

[0310] In some embodiments, after curing, a force is applied to the polymer layer such that the polymer layer is under a compressive stress. In some embodiments, the compressive stress reduces the chemical potential of the lubricating liquid within the polymer. In some embodiments, the compressive stress is sufficient to reduce the chemical potential and to remove a portion of the lubricating liquid from the bulk of the polymer to form a stable overlayer over the surface of the polymer. A compressive stress can be introduced to a polymer layer in any of the methods described herein, for example, as described in the section titled “Controlling formation of a lubricating liquid overlayer by application of stress.”

[0311] In some embodiments, compression can be introduced to the polymers disclosed herein during curing of the polymer layer. In some embodiments, compression can be caused by curing the polymer on a pre-stressed or pre-stretched substrate, e.g., a substrate under tension. A tension can be introduced to a substrate in any of the methods described herein, for example, as described in the section titled “Controlling formation of a lubricating liquid overlayer by application of stress.”

[0312] Disclosed herein is a method of making an article, including: providing a substrate under an external tension caused by an external force; and forming a polymer layer on the substrate under the external tension by: adding a lubricating liquid to one or more polymer precursors, and curing the one or more polymer precursors on the substrate under the external tension to form the polymer layer dispersed with the lubricating liquid on the substrate; wherein the lubricating liquid is added to the polymer precursors at a concentration such that, after forming the polymer layer: the lubricating liquid does not form a stable overlayer on a surface of the polymer layer while the substrate is under the external tension, and releasing the external force causes the polymer layer to be under a first compressive mechanical stress resulting from the residual tension of the substrate, the first compressive mechanical stress being sufficient to cause the lubricating liquid to form a stable overlayer on a surface of the polymer layer.

[0313] In some embodiments, the polymer is porous. In some embodiments, the pore size of the o-polymer can be controlled by adding a portion of miscible but non-binding (i.e., no covalent bonding can be formed) lubricating liquid to the precursor mixture of the o- polymer. In some embodiments, the pores of the o-polymer are nano- or micro-sized.

[0314] In some embodiments, the o-polymer has reduced population of pores compared to pure polymer of same stoichiometry because the added lubricating liquid reduces the viscosity of the precursor mixture. In some embodiments, addition of lubricating liquid in o- polymer promotes coalescence and Ostwald ripening of water droplets before the polymer has completely cured.

[0315] In some embodiments, a polymer is made using a one-pot method in a micro emulsion templating process that includes the lubricating liquid (e.g., silicone oil) in the method. In some embodiments, a porous o-polymer is formed using a micro emulsion templating process in which the lubricating liquid is added during the process. In some embodiments, the disclosed o-polymer is a PDMS matrix with dispersed silicone oil within the bulk of the matrix. In some embodiments, the highest amount of silicone oil incorporated into the o-PDMS system is 200 PHR.

[0316] In some embodiments, a fluorogel-based o-polymer is formed by one-pot method in which lubricating liquid is added to precursors of the fluorogel. In some embodiments, the precursor for fluorogel includes perfluorooctylethyl acrylate (PFOA), PFOEA-50, PFOEA- 50, and PFHEA-95. In some embodiments, the lubricating liquid for fluorogel includes FC- 70 and Krytox 100. In some embodiments,

[0317] In some embodiments, a thermoplastic polymer can be mixed with a lubricating liquid and a plasticizer and formed into the desired end shape by injection molding. In some embodiments, exemplary polymers for use in such applications include low molecular weight polyolefins. In additional examples, LLDPE, LDPE, HDPE, or PP pellets can be compounded with a lubricating liquid such as mineral oil or soybean oil or paraffin and can be molded. In some embodiments, low molecular weight counterpart of each type of polyolefin resins can also serve as a lubricating liquid component when compounding and molding.

[0318] In some embodiments, a composition of a mixture of prepolymers or monomers and lubricating liquid can be formed by various mixing methods. In some embodiments, the composition of the mixture can be pre-conditioned (e.g., aging, soft-baking) to control the viscosity and consistency of the mixture for a selected application method (casting, molding, spraying, etc.). In some embodiments, the mixture can be applied onto a substrate and solidified (photo-curing, thermal-curing, moisture-curing, chemical curing, etc.) to form a shape or a coating layer. In some embodiments, the mixture can be molded to a free-standing 2D (sheets, films) or 3D (tubes, pipes, bottles, containers, optics, and other shapes) objects. In some embodiments, the flowable composition can be applied in a continuous process, for example, by providing a continuous plastic sheet as the substrate, which can be fed out from a supply mandrel and directed into an application zone, where the flowable composition is applied by spraying screen printing dip coating, blade drawing and the like. In some embodiments, the coated plastic sheet optionally can be directed into a second zone where curing is initiated, for example, by exposure to UV or thermal energy.

[0319] In some embodiments, a composition of a mixture of prepolymers or monomers and lubricating liquid can be applied in a continuous process. For example, in some embodiments, the polymer precursor with curing agent and lubricating liquid can be combined and the mixture can be applied to a substrate as it continually passes underneath an applicator. The applicator can spray or paint, squeegee or extrude the composition onto the moving substrate. The substrate can then move into a second zone for curing, e.g., by passing through a heated zone or under irradiation.

[0320] In some embodiments, a composition of a mixture of prepolymer or monomers and lubricating liquid is well-suited for applications on large surfaces, particularly where the underlying surface is irregular and not homogeneous. In some embodiments, the composition can be applied to adhesive-backed films so that the resultant o-polymer coting can be applied as an adhesive strip to other surfaces. In addition, the adhesive o-polymer product can be applied to medical devices and consumer goods where slippery properties are desired.

[0321] In some embodiments, a film including the polymers disclosed herein can be diecut or stamped into desired dimensions. In some embodiments, a film including the polymers disclosed herein can be applied to a surface using methods including roll-to-roll coating, spray casting, and blade-casting.

E. Methods of Controlling Formation of a Lubricating Liquid Overlayer

[0322] Disclosed herein is a method including providing an article comprising a polymer layer and a lubricating liquid within the polymer layer at a concentration such that the lubricating liquid does not form a stable overlayer over a surface of the polymer layer when the polymer layer is not under compressive stress; and applying an external force to the polymer layer such that the polymer layer is under a first compressive mechanical stress sufficient to cause the lubricating liquid to form a stable overlayer on the surface of the polymer layer.

[0323] In some embodiments, the polymers disclosed herein can be designed such that formation of a lubricating liquid overlayer can be controlled by modifying the chemical potential (e.g., by application or release of stress). For example, under some conditions, the surface lubricity or slipperiness can be turned on by increasing the chemical potential such that lubricating liquid is removed from the bulk of the polymer to form a lubricating liquid overlayer, and under other conditions, the surface lubricity can be turned off by decreasing the chemical potential such that lubricating liquid is absorbed into the polymer to remove the lubricating liquid overlayer.

[0324] The ability to control whether an overlayer is formed has several advantages. For example, a polymer incorporating a lubricating liquid can be maintained without an overlayer e.g., in a deactivated state) until installation or use. In some embodiments, maintaining a polymer in a deactivated state can make handling easier, for example, because the polymer is not slippery during installation. In some embodiments, maintaining a polymer in a deactivated state can improve shelf life, for example, because the lubricating liquid can be stored in the bulk, reducing evaporation of the lubricating liquid. In some embodiments, the overlayer can be deactivated when not needed and activated by applying an external force to increase the longevity of the coating. In some embodiments, maintaining a polymer in a deactivated state can improve cleanliness by reducing dust accumulation.

[0325] In some embodiments, surface lubricity can be activated by turning the lubricating liquid layer on or off “on demand” or via “time-release” or delayed release via the application or release of stress.

[0326] In some embodiments, a lubricating liquid overlayer can be turned on by applying an external force to the polymer. An external force can be introduced to a polymer layer in any of the methods described herein, for example, as described in the section titled “Controlling formation of a lubricating liquid overlayer by application of stress.” In some embodiments, the external force includes a component applied in a direction parallel with the surface of the polymer on which the lubricating liquid overlayer is formed. In some embodiments, the external force that turns on the overlayer is a compressive force that increases the chemical potential of the lubricating liquid by causing a compressive stress within the polymer or increasing the compressive stress within the polymer. In some embodiments, the external force is a compressive force and the compressive stress within the polymer includes a component parallel to the external force. In some embodiments, the external force is a stretching force and the compressive stress includes a component in a direction perpendicular to the external force. In some embodiments, the force is biaxial. In some embodiments, the force is uniaxial. In some embodiments, the external force is a compressive mechanical force and polymer is under a tensile mechanical stress that includes a component in a direction perpendicular to the external force.

[0327] In some embodiments, a lubricating liquid overlayer can be turned off by applying an external force to the polymer. An external force can be introduced to a polymer layer in any of the methods described herein, for example, as described in the section titled “Controlling formation of a lubricating liquid overlayer by application of stress.” In some embodiments, the external force that turns off the overlayer includes a component applied in a direction parallel with the surface of the polymer on which the lubricating liquid overlayer is formed. In some embodiments the external force that turns off the overlayer is a tensile force that reduces chemical potential of the lubricating liquid by decreasing the compressive stress in the polymer or by introducing tension to the polymer. In some embodiments, the external force is a tensile force and the stress within the polymer includes a component parallel the external force. In some embodiments, the external force is a compressive force and the stress includes a component in a direction perpendicular to the external force. In some embodiments, the force is biaxial. In some embodiments, the force is uniaxial.

[0328] In some embodiments, the external force can be applied by mechanical stretching, pneumatic inflation (e.g., by altering inflation pressure) or flow-induced pressure (e.g., for a polymer coated on an interior or exterior surface of a pipe). In some embodiments, such a pipe can be flexible and capable of expanding under internal pressure. In some embodiments, a polymer can be disposed on a substrate, and an external force can be applied by stretching or compressing the substrate. In some embodiments, the external force is caused by pressurizing the polymer layer (e.g., by putting the polymer layer under a hydrostatic pressure). In some embodiments, the external force is applied by bending the polymer layer. For example, bending a polymer layer can introduce compressive stress in a first region of the polymer layer and tension in a second region of the polymer.

[0329] In some embodiments, an external force can be applied locally to form a lubricating liquid overlayer over a portion of the polymer. In some embodiments, an external force can be applied locally using an indenter.

[0330] In some embodiments, an external force can be applied by applying a stimulus to the polymer layer or substrate. In some embodiments, a compressive stress can be caused by applying a stimulus to the polymer layer or substrate. In these embodiments, the polymer layer includes a stimuli-responsive polymer or substrate. In some embodiments, stimuli- responsive materials can change their shape and/or dimensions, thereby introducing a compressive stress, in response to one or more stimuli through external influences: for example, the effect of light, temperature, pressure, an electric or magnetic field, or a chemical stimulus. In some embodiments, the chemical stimulus is a cross-linking agent or a swelling agent. In some embodiments, the polymer layer or substrate includes a shape memory alloy. In some embodiments, a shape-memory alloy changes its shape in response to a stimuli: for example the effect of light, temperature, pressure, an electric or magnetic field, or a chemical stimulus. For example, a compressive stress can be caused by a shape change of a shape memory alloy embedded within or disposed on a polymer layer. For example, a polymer layer can be coated onto a medical device (e.g., a stent) that includes a shape memory alloy.

F. Applications

[0331] In some embodiments, a silicone polymer containing an oil serves as a fouling-release coating for marine applications. In some embodiments, the silicone polymer containing the oil is used for prevention and removal of marine biofouling on submerged surfaces. In some embodiments, the silicone polymer containing the oil is used as a foulingrelease (FR) coating, which minimizes the adhesion of marine fouling organisms. In some embodiments, the silicone polymer containing the oil incorporates amphiphilic properties, hybrid material approaches, or active substances. In some embodiments, the silicone polymer containing the oil not only improves the FR coating performance, but is also biodegradable.

[0332] In some embodiments, a polymer layer containing a lubricating liquid serves as a fouling-release coating for marine applications. In some embodiments, the polymer layer containing the lubricating liquid is used for prevention and removal of marine biofouling on submerged surfaces. In some embodiments, the polymer layer containing the lubricating liquid is used as a fouling-release (FR) coating, which minimizes the adhesion of marine fouling organisms.

[0333] In some embodiments, the exemplary applications of disclosed o-polymer include an anti-ice coating for the lower section of roofs, an anti-fouling coating on cooling towers, marine structures, an anti-graffiti coating on walls, signs, and other outdoor structures, an anti-sticking surface finish, particularly to large surface areas, as anti-fouling tubes and pipes (e.g. medical catheters, biomass/biofuel producing reservoirs, such as algae-growing trays and tubes), aquarium windows coated with o-polymer for anti-fouling, as self-cleaning optics and as self-cleaning and easy-cleaning coating on optics, windows, solar panels.

[0334] In some embodiments, exemplary applications of the disclosed o-polymer include medical devices, including medical implants, stents, and silicone implants.

[0335] In some embodiments, exemplary applications include deployable structure, e.g., tents or inflatables.

EXAMPLES

[0336] Certain embodiments will now be described in the following non-limiting examples.

A. Comparison of stress-free o-PDMS to i-PDMS at the same concentration

1. Materials preparation

[0337] Preparation of PDMS coating: Sylgard 184 elastomer kit (Dow Corning Corporation, Midland, MI) was used in the production of the tested silicone coatings. The base (part A) and curing agent (part B) were combined in a 10: 1 ratio (A:B) and mixed in a planetary centrifugal mixer (Thinky Corporation, Tokyo, Japan) at 2000 rpm for 1 min, followed by a second mixing step at 2200 rpm for 1 min. After mixing, 10 g of elastomer mixture was applied to the surface of 1.5 cm steel discs (NDSU bacterial biofilm assays), 4” x 8” steel plates (NDSU mussel/barnacle assays and Port Canaveral, Morro Bay and Singapore Harbor field studies), and 1/8” thick, 6 ^14/16 ”x 6 ^14/16 ” glass plates (Scituate Harbor field study). They were then surface activated using a 2 min, 250W, oxygen plasma (Femto PCCE plasma cleaner, Diener electronic GmbH, Ebhausen, Germany). Excess silicone prepolymer was removed by spinning slides at 1000 rpm for 60 s via spin coating (Spincoat G3P-15, SCS, Indianapolis, USA) to achieve an approximate -100pm thickness. For the 1.5 cm stainless steel tokens, 3 droplets were applied to the surface from the tip of a spatula and excess prepolymer was removed using a smaller spin-coater setup (Laurell Technologies Corporation, North Wales, PA). After spin-coating the samples were cured in an oven (Binder GmbH, Tuttlingen, Germany) at 70°C for 4 h.

[0338] Preparation of o-PDMS: Sylgard 184 elastomer kit was used to prepare one-pot PDMS treatments as described above. Immediately after, Element 14* PDMS 10-A silicone oil (Momentive, Waterford, NY) was added to the 10: 1 PDMS prepolymer at a mass loading equal to 50% of the prepolymer mass (the same oil content as infused silicone SLIPS) before mixing using the planetary mixer. For example, 5 g of PDMS oil were added to 10 grams of uncured 10: 1 PDMS. After mixing, 10 g of elastomer mixture was applied to the surface of 1.5 cm diameter steel discs (NDSU bacterial biofilm assays), 4” x 8” steel plates (NDSU mussel/barnacle assays and Port Canaveral, Morro Bay and Singapore Harbor field studies), and 1/8” thick, 6 ^14/16 ”x 6 ^14/16 ” glass plates (Scituate Harbor field study). The surface was then activated using a 2 min, 250W, oxygen plasma. Excess silicone prepolymer was removed by spinning at 300 rpm for 60 s via spin coating. After spin-coating, the samples were cured in an oven at 70°C for 4 h.

[0339] Preparation of i-PDMS: Infused silicone slippery coatings were prepared using the PDMS methods specified above, followed by the subsequent infusion of Element 14* PDMS 10-A into the cured PDMS matrix. The cured PDMS surface was first flooded with an overlayer of Element 14* PDMS 10-A and left to infuse at room temperature for 48h to allow the lubricating liquid to fully infiltrate and equilibrate throughout the silicone polymer matrix. Excess lubricating liquid was subsequently removed from the surface before testing by either spin coating samples at 1000 rpm for 60 s, or allowing the excess lubricating liquid to be drained by gravity by tilting the samples at a 90° angle for 24 h.

[0340] Preparation of INTERSLEEK 700 : Intersleek 700 (International Marine

Coatings, Akzo Nobel) was prepared according to manufacturer specifications: Intersleek 757 topcoat was mixed in 15:4: 1 (A:B:C) ratios and mixed by hand using a glass stir rod. This mixture was applied via spin coating at 750 rpm for 60 seconds to achieve a coating thickness of ~150pm on the discs, steel plates, and glass plates. The surfaces were then activated using a 2 min oxygen plasma exposure at 250W. Coatings were left to cure for at least 2 days at room temperature before testing.

2. Materials characterization

[0341] AFM detection of lubricating liquid layer: i-PDMS, o-PDMS and PDMS control surfaces were investigated using atomic force microscope (AFM) (JPK instruments, CellHesion200) using cantilevers (BudgetSensors) with spring constant of 5.45 N/m. The setpoint was 19.74 nN, the pulling length was 20 pm and the extent speed was 1 pm/s.

[0342] Results: The i-PDMS and o-PDMS coatings each contain ~ 50 wt% free silicone oil within the PDMS matrix. Observed differences in material properties arise from the fabrication process of the coatings, where the oil is added either before curing (o-PDMS) or infused into the polymerized material after curing the PDMS matrix (i-PDMS).

[0343] The i-PDMS, o-PDMS, and oil-free PDMS control coatings were adhered to a steel or glass substrates. The coating thickness was initially set at ~ 100 pm for PDMS control and o-PDMS coatings. Due to the swelling process involved in the production of the i-PDMS from the PDMS control coating, the i-PDMS coating thickness increased to ~ 150 pm. The Intersleek 700 treatment also produced a coating with the thickness of - 150 pm according to manufacturer instructions.

[0344] The i-PDMS surface appeared coated with a lubricating liquid overlayer (LOL) that was stable in air and resisted basic removal attempts such as exposure to running water. In contrast, the o-PDMS coating did not display any lubricating liquid on the coating surface (FIG. 5C). While the water contact angles (CA) for i-PDMS and o-PDMS were similar (113° ± 0.7° and 110.4° ± 1.1°, respectively), the coatings showed a greater difference in terms of contact angle hysteresis (CAH) (2.1° ± 0.7° for i-PDMS and 8.9° ± 2.6° for o-PDMS), indicating a higher degree of slipperiness and lower water pinning for the i-PDMS treatment. [0345] FIG. 5 A shows the shear modulus of i-PDMS (white bar) and o-PDMS (gray bar). After lubricating liquid infusion and the removal of excess lubricating liquid (through centrifugal force or drainage), i-PDMS was measured to be 2.4 times stiffer than o-PDMS (through nano-indentation) due to the swelling of the i-PDMS coating.

[0346] FIGS. 5B-5C show lubricating liquid overlayer detection using atomic force microscopy (AFM) for o-PDMS (FIG. 5C) and i-PDMS (FIG. 5B). The light grey curve represents the “extend” curve (the AFM tip approaching and then contacting the sample). The dark is the inverse “retract” curve, showing the adhesive force experienced by the AFM tip. This adhesive force is much higher for i-PDMS (~ 26 nN) compared to o-PDMS (~ 5 nN) due to the presence of the lubricating liquid layer on i-PDMS.

3. Laboratory-based biofouling characterization

[0347] The biofouling performance of four distinct elastomeric anti-adhesive coatings (i- PDMS, o-PDMS, Intersleek 700 and PDMS control) were compared under laboratory conditions, following accepted Office of Naval Research (ONR) and industrial testing procedures. The testing was done with single species adhesion, attachment and retraction experiments making use of the adhesion properties of bacteria (Cellulophaga lytica), diatoms (Navicula incerlci). mussels (Geukensia demissa) and barnacles (Amphibalanus amphitrite).

[0348] Laboratory biofouling characterization: Prior to biofouling assessments, all coatings prepared on 24-well plates containing 1.5 cm disc samples and 4” x 8” steel plates were immersed for 7 days in a running tap water tank system. Growth assessments in artificial sea water (ASW) extracts of each coating were subsequently carried out to verify that no toxic components were leaching from the materials.

[0349] Bacteria Biofilm Retraction (Cellulophaga lytica)'. The characterization of bacteria biofilm retraction on coatings prepared in 24-well plates has been described in detail previously. Briefly, overnight cultures of the marine bacterium Cellulophaga lytica in marine broth were harvested via centrifugation (10,000xg for 10 minutes) and rinsed three times with sterile artificial seawater (ASW). The bacteria were then re-suspended in ASW supplemented with 0.5 g/L of peptone and 0.1 g/L of yeast extract to achieve a final cell density between 107-108 cells/mL. One mL of bacterial suspension was added to each well and incubated at 28 °C for 24 hrs under static conditions to promote cell attachment and biofilm growth. The coatings were subsequently rinsed three times with ASW, allowed to air dry at ambient laboratory conditions for ~1 h, stained with a crystal violet (CV) dye solution (0.3% w/v) for 15 min, rinsed three times with ASW, and air dried. The degree of biofilm retraction on each coating replicate was measured using an automated software tool that calculated the percent surface coverage of CV-stained biofilms from high resolution digital images 4 where a low percent surface coverage indicates a high degree of biofilm retraction.

[0350] Microalgae Cell Attachment (Navicula incerta)'. The characterization of microalgae cell attachment to coatings prepared in 24-well plates has been described in detail previously. Briefly, five-day-old cultures of the microalgae (diatom) Navicula incerta were rinsed three times with ASW and re-suspended in Guillard’s F/2 medium to achieve a final cell density of 105 cells. ml ^-1 . One ml of the microalgae suspension was added to each well of the coated plates and incubated statically at 18°C for 2 h in an illuminated growth chamber (photon flux density 46 pm m ^-2 s ^-1 ). The microalgae suspension was subsequently discarded, the coatings were extracted with 1.0 ml of dimethyl sulfoxide for 15 min, and the resulting eluates were transferred to 96-well plates and measured for fluorescence of chlorophyll (Ex: 360 nm; Em: 670 nm) using a Tecan Safire 2 multi-well plate spectrophotometer.

[0351] Barnacle Reattachment and Adhesion (Amphibalanus amphitrite)'. The laboratory assessment of adult barnacle reattachment and adhesion has been described previously. In our tests, 5 adult barnacles (Amphibalanus amphitrite) of a testable size (>5mm basal diameter) were dislodged from glass panels coated with Silastic T2 and placed on the coated 4”x8” steel plates. Immobilization templates were then applied to each panel to anchor barnacles to the coated surfaces and then transferred to an artificial saltwater aquarium tank system. The reattached barnacles were fed daily with freshly hatched brine shrimp nauplii (Anemia sp.). After 14 days of reattachment in the aquarium system, the steel plates were removed and the reattached barnacles were removed in shear mounted to a semiautomated push-off device to measure the peak force at release. The area of the barnacle base plates were measured using a Sigma Scan Pro software package (SigmaScan Pro 5.0, Systat Software, Inc., Richmond, CA). The adhesion strengths were then calculated by normalizing detachment shear force to basal area. Barnacle adhesion for each coating was reported as the mean value of the total number of barnacles that had a measurable detachment force. Barnacles that had no measurable force for detachment were counted as “not attached” and not included in adhesion calculations.

[0352] Marine Mussel Attachment and Adhesion (Geukensia demissa): The assessment of marine mussel attachment and adhesion was carried out using a customized protocol derived from previously published methods. Freshly collected adults of the ribbed mussel Geukensia demissa (3-5 cm in size) were obtained from the Duke University Marine Laboratory in Beaufort, North Carolina, USA, and housed in an ASW aquarium tank system with continuous monitoring and maintenance of pH (8.0-8.2) and salinity (35 ppt). Prior to attachment studies, a 4 cm section of acetal plastic rod (product# 98873 Al 05, McMaster- Carr) was adhered to the shell of each mussel, perpendicular to the ventral edge, using a 3M acrylic adhesive (product# 7467A135, McMaster-Carr). Custom-designed templates fabricated from PVC sheets were then used to immobilize six mussels onto each coated 4”x8” steel plate, using setscrews to firmly secure the adhered, plastic rods. The samples were placed in the ASW aquarium system and the mussels were fed daily with live marine phytoplankton (DTs Premium Reef Blend Phytoplankton). After three days of immersion, the mussels were removed from the ASW aquarium tank system and the total number of mussels exhibiting attachment of byssus threads was recorded for each surface. The rod of each attached mussel was then secured to an individual 5N load cell of a custom-built, tensile force gauge outfitted with six load cells to enable simultaneous measurements of all attached mussels. The total force required to detach the byssus threads for each mussel was recorded (1 mm/s pull rate) and the average pull-off force value (Newtons) for all attached mussels was calculated for each coating surface.

[0353] Results: FIGS. 6A-6D show comparative performance of o-PDMS, i-PDMS, Intersleek 700 and a PDMS control coating (PDMS with no coating) in marine fouling assays. FIGS. 6A-6D show surfaces tested for anti-adhesion performance against bacteria (Cellulophaga lytica (N = 3) (FIG. 6A, biofilm surface coverage in Z%), microalgal diatoms (Navicula incerta) (N = 4) (FIG. 6B, fluorescence intensity in RFU), mussels (Geukensia demissa) (N = 6) (FIG. 6C, mussel adhesion in Newtons), and barnacles (Amphibalanus amphitrite) (N = 6) (FIG. 6D, adhesion strength in MPa). Error bars indicate standard deviation (SD) and * indicates no adhesion took place.

[0354] As shown in FIG. 6A, the i-PDMS coating had the best performance in the C. lytica biofilm retraction assay and had the smallest remaining biofilm coverage (7.41% ± 5.74%), followed by Intersleek 700 (34.74% ± 22.83%). PDMS control and o-PDMS showed no retraction at all in this assay.

[0355] As shown in FIG. 6B, one of the coatings showed a strong performance in the N incerta microalgal assay, with only Intersleek 700 showing a slightly reduced fluorescence intensity (4811 RFU ± 75 RFU), indicating lower microalgal attachment to the coating. [0356] As shown in FIG. 6C, during the G. demissa adhesion assay none of the mussels adhered to the i-PDMS coating, further supporting the strong performance of i-PDMS against this particular group of hard-fouling organisms. In comparison, mussels readily adhered to PDMS control, IS700 and o-PDMS during the assay.

[0357] As shown in FIG. 6D, i-PDMS was also the best performing coating in the A. amphitrite barnacle adhesion assay, with barnacle adhesion strength to the i-PDMS (0.018 MPA ± 0.003 MPA) being significantly lower than that of PDMS control, o-PDMS and Intersleek 700.

[0358] In summary, i-PDMS showed a significantly stronger fouling-release performance than o-PDMS during all assays, with the exception of the N incerta microalgal assay, where neither of the two coatings performed differently from the PDMS control. The results summary and the statistical analysis for the laboratory studies can be found in Tables 2-6.

Table 2. Results summary table for the laboratory fouling assays, showing means and standard deviation of each coating tested. H = comparison with average historical adhesion data, due to Intersleek 700 coating failure (poor batch performance).

Table 3. unpaired t-test results for C. lytica. Table 4. unpaired t-test results for N incerta.

Table 5. unpaired t-test results for G. demissa.

Table 6. unpaired t-test results for A. amphitrite.

4. Field study methods and biofouling characterization a. Scituate Harbor, MA, USA

[0359] Field site (Scituate Harbor, MA, USA): The Scituate Harbor field site

(42°11’55” N, 70°43’5” W) is located on the land-ward facing site of a small peninsula with direct access to the Atlantic Ocean. It consists of two floating docks attached to a pier facility owned and maintained by the Stellwagen Bank National Marine Sanctuary (NOAA). The site was chosen as it receives substantial and regular tidal flushing, while at the same time being protected by a seawall from direct wave impact. The site shows a diverse biological community, typical of the Northeastern Atlantic coast, dominated by mussels (Mytilus edulis), tunicates and hydroids during the summer season when the experiments were performed and an assembly of microalgae and filamentous brown macroalgae during the autumn / winter seasons.

[0360] Field survey methodology and fouling observations (Scituate Harbor): PVC settlement panels were placed through slots of a floating raft, moored to a floating dock, maintaining a constant submersion depth of samples of 0.5 m. Each panel had four retaining frames, coated with anti-fouling copper paint (ACT, Interlux, Akzo Nobel) to reduce the edge effect, used for securing the 175 x 175 mm ² glass settlement plates to each of the panels. Field observational surveys were conducted every other week during the entire summer testing season, when the mussel attachment takes place. Surveys were conducted every two weeks. The panels containing test substrates were removed from the water and photographed horizontally, observations in fouling and coating condition were also made while the panel was out of the water. A white balance card (Digital Kolor Kard 5x7, DGK Color Tools, Boston, USA) was included in each photo taken. The in-air survey time of each panel was limited to 10 min, before returning the panels to the water, minimizing the survey impact on community development.

[0361] Image analysis (Scituate Harbor): Preprocessing of the photos was conducted using a python script, to perform a white balance, vignette removal and 0.5 inch crop of the sample edge on each image. Subsequently the images were loaded into Coral Point Count with Excel extensions (CPCe 4.1) from the National Coral Reef Institute (NCRI) at Nova Southeastern University. Using CPCe, 50 random points were overlaid on top of the image and the marine fouling organism attached at each point was identified by a user trained in the identification of marine benthic communities. The graphs showing the community composition were plotted using Excel (Microsoft Corporation).

[0362] Mussel settlement counts (Scituate Harbor): The quantification of the mussel settlement was conducted with the photos taken during week 8 field survey, when the mussel spat reached a sufficient size to be visible on the high-resolution images. Each image was divided into 100 squares of equal size (2.32 cm ² ). Five randomly selected squares were taken per image and all mussels found in these squares were manually counted using a Tally Counter. Subsequently an estimate of the mussel spat per cm ² was made based on these counts. [0363] Results (Scituate Harbor): As shown in FIGS. 7A-7D, regular (bi-weekly) access to Scituate field site allowed for a high temporal resolution study of the fouling community development over a 6-month period (May-November 2014). FIGS. 7A-7D show fouling coverage and composition on PDMS control (FIG. 7A), Intersleek 700 (IS700) (FIG. 7B), o-PDMS (FIG. 7C), and i-PDMS (FIG. 7D) over a 6-month emersion period at Scituate Harbor, MA. FIGS. 7A-7D show % coverage by slime, solitary tunicates, red algae, green algae, colonial tunicates, hydroids, brown algae, mussels, encrusting bryozoans, and composite fouling (combination of hard and soft fouling organisms growing on top of another). Combination fouling is considered to be the heaviest, most problematic fouling category.

[0364] FIG. 8 shows representative images of the treated panels (17.5 cm * 17.5 cm) showing the fouling trends observed on each coating (PDMS control, Intersleek 700 (IS700), o-PDMS, and i-PDMS) after 4 weeks, 8 weeks, 12 weeks, 16 weeks, 20 weeks, and 24 weeks. The number of samples for each coating type (N) = 5.

[0365] As shown in FIGS. 7A-7D and FIG. 8, the first fouling community to establish was a thin biofilm (or ‘slime’) on all surfaces until week 4. From week 6 onwards these biofilms started to recede, and mussel spat (Mytilus edulis) started to settle on all coatings. [0366] As shown in FIGS. 9A-9B, the settlement of the mussels was quantified at week 8, when the mussel spat was large enough to be counted (approximately 0.5 mm in length). FIG. 9A shows mussel spat densities on PDMS, IS700, o-PDMS and i-PDMS treatments in week 8 (Error bars = standard deviation, SD). FIG. 9B shows representative images on the mussel spat accumulation patterns on each treatment type (PDMS, IS700, o-PDMS and i- PDMS) in week 8 (Full panel scale bar = 5 cm, inset scale bar = 1 cm, number of samples (N) = 5). Note that on i-PDMS surface, mussel spat generally forms on remnants of the retracted biofilm, as shown in insets. The aggregation patterns of the mussels differed between the coatings. On the PDMS control the mussel spat settled densely and spread out over the coating surface. On o-PDMS and Intersleek 700, the mussel spat showed a clumped distribution.

[0367] As shown in FIG. 9B, very few mussels settled on i-PDMS and their presence appeared largely limited to retracted biofilm remnants, rather than the coating surface itself. In agreement with the laboratory assays shown in FIG. 6C, the total number of mussels settled was significantly different (a < 0.05) between all treatments with the lowest numbers of mussels settling on i-PDMS (3.4 ± 2.6 mussels/cm ² ), followed by Intersleek 700 (14.3 ± 7.3 mussels/cm ² ), o-PDMS (39.3 ± 23.1 mussels/cm ² ) and PDMS control (99.1 ± 46.8 mussels/cm ² ) (FIG. 9A). The results summary and the statistical analysis for the mussel spat densities can be found in Tables 7 and 8.

Table 7. Mussel spat densities in Scituate Harbor, MA.

Table 8. unpaired t-test results for Mussel spat densities.

[0368] As shown in FIGS. 7A-7D, over the following weeks and months, the fouling communities developed differently on each coating. The small number of mussels attached to i-PDMS disappeared completely by week 12, with most of the coating surface (65%-80%) remaining free of fouling until week 18 (early October) when thicker algae biofilms started to cover most of the coatings surface. The initial 16-week delay in fouling build-up was at least partially due to strong biofilm retraction effects (similar to the ones depicted in laboratory assays shown in FIG. 6A), which removed most of the attached fouling at each sampling point. Aside from i-PDMS, no other coating showed any biofilm retraction effects.

[0369] The mussel communities attached to Intersleek 700 grew until week 16, after which most of the mussel disappeared from the coatings surface. Mussel coverage never exceeded more than 10% on Intersleek 700 during the study. The coatings surface was mostly dominated by thin biofilms during the study period, with some colonial tunicate, soft- fouling coverage (up to 20%). By the end of the study, most of the surface was covered in thick algal biofilms with no mussels and little (< 5%) colonial tunicate coverage remaining by week 26.

[0370] The mussel communities on o-PDMS grew substantially, until its coverage was > 50% by week 16. Thereafter, the increased weight of the mussels led to a series of foulingrelease events, some of which took place during the field surveys of the coated panels. Mussel coverage declined drastically until week 26, when most (> 80%) of the o-PDMS surface was covered in a thick algal biofilm, with little (< 5%) mussel and low (< 10%) colonial tunicate coverage remaining.

[0371] The mussel communities on PDMS control expanded rapidly after settlement in week 6 and by week 16, > 70% of the coatings surface was covered. The mussel fouling on PDMS control followed the seasonal trend seen on the other coatings and declined towards the end of the study (weeks 22-26). Nevertheless, remaining mussel coverage was highest > 35% on PDMS control, with substantial algae biofilm (> 50%) and little colonial tunicate coverage (< 5%) also being present by week 26.

[0372] In summary, i-PDMS showed the most promising performance at the Scituate Harbor field site, effectively preventing the build-up of the dominant mussel community and delaying the onset of fouling for a period of 4 months. While o-PDMS did not prevent the build-up of the mussel community, it showed sufficient fouling-release properties by the end of the study. In contrast, the PDMS control only showed limited fouling release properties and retained half of its hard-fouling coverage. b. Morro Bay, CA, USA

[0373] Field site (Morro Bay, CA, USA): The Cal Poly test site is located near the mouth of Morro Bay (35°22'10" N, 120°51'48” W) and is subjected to a temperate marine environment. It is a floating dock that raises and lowers with the tidal cycle so the panels remain at a constant depth of approximately one meter. The temperature and salinity fluctuate seasonally from 11.2-22.3°C and 13-35%o. Morro Bay’s fouling community is diverse and changes seasonally. Barnacle recruitment usually occurs from summer to early fall and late winter to spring. The heaviest fouling occurs between spring and fall. The fouling community consists of sponges, tunicates, tubeworms, hydroids, anemones, tube-dwelling amphipods, arborescent and encrusting bryozoans and several species of barnacles, the most abundant of which is Balanus crenatus. The most dominant species is an invasive encrusting bryozoan Watersipora subtorquata. [0374] Fouling observations (Morro Bay, Port Canaveral, Singapore Harbor):

Digital photographs of each panel replicate were taken on a monthly basis. Percent coverage of fouling organisms were visually estimated in the field for each replicate according to ASTM D6990-05. Panel edges were blocked out to eliminate any potential edge effects so the area of each panel assessed lies within the rectangular area lying within the corner holes. Total fouling coverage and composition was visually estimated in the field.

[0375] Hard-fouling field adhesion studies (Morro Bay and Port Canaveral): Hard- fouling adhesion studies of barnacles were conducted according to ASTM D5618-94 by selecting life barnacles, applying shear force to the base of the organism and measuring the removal force. Adhesion failure must be between the organism and the surface for a reading to be valid. The removed organisms are retained and returned to the laboratory where their base plate is measured with a scanner or from measurements of the basal plate diameter in the field. The shear strength of adhesion (MPa) is calculated by dividing the force of removal (Newtons) by the area of the organism base (square millimeters). At the Morro Bay field site this methodology has been adapted for the use on encrusting bryozoans.

[0376] Results (Morro Bay): The field experiments in Morro Bay were conducted over a 15-month period from May 2015 until September 2016. In addition to the static immersion fouling studies, encrusting bryozoan adhesion and barnacle adhesion studies were conducted in July and August 2015, respectively.

[0377] FIGS. 10A-10D show fouling trends on PDMS (FIG. 10A), IS700 (FIG. 10B), o- PDMS (FIG. 10C), and i-PDMS (FIG. 10D) in Morro Bay over a 15-month immersion period from May 2015 to September 2016. FIGS. 10A-10D show % coverage by soft fouling, hard fouling, and biofilm. The black line in each dataset corresponds with a pressure washing treatment in March 2016 removing all adhered fouling. Any growth from April 2016 onwards represents a newly established fouling community after pressure-washing the panels. Number of samples (N) = 5.

[0378] As shown in FIGS. 10A-10D, over this period, both hard-fouling communities (encrusting bryozoan- and barnacle-dominated) and soft-fouling communities (colonial tunicate- and hydroid-dominated) developed on the coatings. Overall fouling coverage was lowest on the i-PDMS treatment (FIG. 10D), which maintained areas free of fouling throughout the entire study period. Interestingly, i-PDMS showed the same 4-month fouling delay previously seen in the Scituate Harbor study (FIG. 7D). Furthermore, while barnacles established themselves readily on IS700, o-PDMS and PDMS, there was little to no barnacle coverage on i-PDMS and the hard-fouling community on this coating was largely limited to encrusting bryozoans. In comparison, as shown in FIG. 10B, Intersleek 700 showed elevated hard and soft fouling after one month into the study. Neither o-PDMS (FIG. 10C) or PDMS control (FIG. 10 A) showed any particular fouling-prevention performance.

[0379] FIGS. 11 A-l IB show encrusting bryozoan and barnacle adhesion strength to PDMS, IS700, o-PDMS and i-PDMS in Morro Bay. Error bars = standard deviation (SD). As shown in FIG. 11 A, i-PDMS also performed best during the hard-fouling adhesion tests (bryozoan and barnacle adhesion strength), as significantly less force was required to remove encrusting bryozoans from the coatings surface than from o-PDMS, Intersleek 700 and the PDMS control. The evaluation of barnacle adhesion strength on i-PDMS compared with the other coatings could not be conducted, as there was no barnacle settlement on i-PDMS during the study period. As shown in FIG. 1 IB, barnacle adhesion was significantly lower on Intersleek 700 than on o-PDMS and significantly lower on o-PDMS than on the PDMS control. The results summary and the statistical analysis for the encrusting bryozoan and barnacle adhesion can be found in Tables 9-11.

Table 9. Summary table of the encrusting bryozoan and barnacle adhesion studies in Morro Bay, showing means and standard deviations of all tested coatings.

Encrusting bryozoan adhesion Barnacle adhesion

N j (in N/mnf) (in N/mm ² )

3 | 0.165 ± 0.012 0.299 ± 0.023 |

8 | 0.077 ± 0.009 0.109 ± 0.015 |

3 | 0.094 ± 0.017 0.186 : 0.015 | 3 [ 0-03 ±0-001 0 (no barnacles) §

Table 10. unpaired t-test results for encrusted bryozoan adhesion analysis.

Table 11. unpaired t-test results for encrusted bryozoan adhesion analysis. c. Port Canaveral, FL, USA

[0380] Field site (Port Canaveral, FL, USA): The FIT field site is located inside Port Canaveral (28°24'27" N, 80°37'38" W) along the central east coast of Florida. The port was created in 1953 and is a hub for cruise and cargo ships, US Navy, Coastguard, fishing vessels and recreational boats. The site is located in a subtropical environment and the water temperature fluctuates between 20-32 deg C, with an average salinity of 35 ± 1.2 ppt. It is an area of high fouling activity with seasonal variation in fouling organisms. The biofouling community in warmer months is dominated by calcareous tubeworms, barnacles, colonial tunicates, and encrusting bryozoans. In cooler months, biofilms and arborescent bryozoans dominate.

[0381] Fouling observations (Morro Bay, Port Canaveral, Singapore Harbor):

Digital photographs of each panel replicate were taken on a monthly basis. Percent coverage of fouling organisms were visually estimated in the field for each replicate according to ASTM D6990-05. Panel edges were blocked out to eliminate any potential edge effects so the area of each panel assessed lies within the rectangular area lying within the corner holes. Total fouling coverage and composition was through image analysis using CPCe 4.1 with 50 random sample point estimate method.

[0382] Hard-fouling field adhesion studies (Morro Bay and Port Canaveral): Hard- fouling adhesion studies of barnacles were conducted at Port Canaveral according to ASTM D5618-94 by selecting life barnacles, applying shear force to the base of the organism and measuring the removal force. Adhesion failure must be between the organism and the surface for a reading to be valid. The removed organisms are retained and returned to the laboratory where their base plate is measured with a scanner or from measurements of the basal plate diameter in the field. The shear strength of adhesion (MPa) is calculated by dividing the force of removal (Newtons) by the area of the organism base (square millimeters).

[0383] Results (Port Canavaral): Barnacle (mostly Balanus eburneus) hard-fouling adhesion was tested after 4 and 7 months (in September and December 2015) of immersion, respectively. FIG. 12 shows barnacle adhesion strength to PDMS, IS700, o-PDMS and i- PDMS at Port Canaveral after 4- and 7-months static immersion, number of samples (N) = 6. Error bars = standard deviation (SD). At these time points, all coatings, including a copperbased AF paint reference control, were completely covered in a thick layer of colonial tunicates which needed to be removed before any hard-fouling measurements could be attempted. The results summary and the statistical analysis for the barnacle adhesion in month 4 and 7 can be found in Tables 12-14.

[0384] As shown in FIG. 12, the subsequent adhesion measurements produced a clear trend with i-PDMS showing the lowest barnacle adhesion strength, followed by Intersleek 700, o-PDMS and PDMS control. This performance trend therefore follows the same pattern as the fouling community development, mussel recruitments and hard-fouling adhesion studies conducted in Scituate Harbor, Morro Bay and laboratory assays.

Table 12. Summary table of the barnacle adhesion studies in Port Canaveral, showing means and standard deviations of all tested coatings.

Table 13. unpaired t-test results barnacle adhesion (month 4).

Table 14. unpaired t-test results barnacle adhesion (month 7). d. Singapore Harbor, Singapore

[0385] Field site (Singapore Harbor, Singapore): The TMSI test site is located at the Republic of Singapore Yacht Club (RSYC) on the south-west coast of Singapore (1° 17’40” N, 103°45’37” E). Surface water temperatures are relatively high for most part of the year, ranging between 27 to 31 °C. Salinities in the near-coastal areas are typically estuarine, and fluctuate between 20-30 ppt. The most common hard macrofouling organisms observed at the site on panels during the period were tubeworms. Several species of serpulid tubeworms may be found at the test site, especially on unprotected surfaces, including Spirobranchus krausii, Hydroides spp. and Ficopomatus sp. Spirorbid worms were typically abundant throughout the year. Three species of barnacles, Amphibalanus reticulatus, A. cirratus and A. amphitrite occur. The most common mollusc occurring on the panels were Dendrostrea cf. foliaceum and Anomia sp. Soft-fouling on the panels was dominated by encrusting sponges and colonial tunicates. Bryozoans such as Bugula sp. occurs sporadically but the actual fouling cover recorded is always low as the area of contact with the panel surfaces is small and they are usually attached to secondary substrata. Slime coverage was aggressive on all substrates especially during the NE monsoon months.

[0386] Fouling observations (Morro Bay, Port Canaveral, Singapore Harbor):

Digital photographs of each panel replicate were taken on a monthly basis. Percent coverage of fouling organisms were visually estimated in the field for each replicate according to ASTM D6990-05. Panel edges were blocked out to eliminate any potential edge effects so the area of each panel assessed lies within the rectangular area lying within the corner holes. Total fouling coverage and composition was visually through image analysis using Photogrid 1.0 (Singapore with 50 random sample point estimate method.

[0387] Results (Singapore Harbor): The fouling pressure at the Singapore site resulted in clear differentiation between coatings over the 24-month test period (June 2015 - May 2017). Over this period, the development of hard-fouling communities (mostly oysters, barnacles and tubeworms), soft-fouling communities (mostly macroalgae, sponges and tunicates) and microalgal biofilms (‘slime’) on the different coatings was monitored monthly. [0388] As shown in FIGS. 13A-13D, the long-term (2 year) fouling-prevention performance of the coatings in Singapore followed similar trends to those seen in the Scituate study. FIGS. 11 A-l ID show fouling coverage and composition on PDMS control (FIG.

13A), Intersleek 700 (IS700) (FIG. 13B), o-PDMS (FIG. 13C), and i-PDMS (FIG. 13D) over a 24-month emersion period at Singapore Bay. FIGS. 13A-13D show % coverage by soft fouling, hard fouling, and biofilm. As shown in FIGS. 13B and 13D, the i-PDMS and Intersleek 700 treatments effectively prevented the development of hard fouling communities on coating surface. Over the 24-month study period, the fouling communities on both coatings are largely dominated by microalgal biofilms, confirming the results of the laboratory microalgae assay that showed significant diatom adhesion to all coatings (FIG. 6B). Soft fouling was largely absent in the first year of the study (< 10% coverage) but became more prominent in the second year with a maximum soft-fouling coverage of - 20% on i-PDMS and - 45% on IS700.

[0389] The o-PDMS and the PDMS control treatments did not prevent the establishment of a hard-fouling community. A continuous hard-fouling coverage developed on these coatings 2-4 months into the study. Maximum hard-fouling coverage is > 25% for o-PDMS and > 55% for the PDMS control. In addition, both coatings develop a soft-fouling coverage with the majority of the o-PDMS and PDMS control surfaces being covered by macrofouling towards the end of the study. However, the buildup of the macrofouling community was slower for the o-PDMS (19 months until > 50% macrofouling coverage) coatings than for the PDMS control (5 months until > 50% macrofouling coverage).

[0390] In summary, the Singapore field results support the general performance trend seen in the Scituate field study and in laboratory assays, with i-PDMS showing the best fouling prevention performance, followed by IS700, o-PDMS, and the PDMS control exhibiting the least fouling prevention performance. [0391] Statistical analysis: The statistical analysis and bar charts of the adhesion and count data was conducted with GraphPad Prism 8.0.2. Comparative analysis between the treatments was conducted as unpaired t-tests.

5. Comparing the performance of o-PDMS and i-PDMS at the same concentration of silicone oil using Flory-Rehner theory

[0392] From the results presented, the pre-cure (one-pot) addition of a compatible free silicone oil to a PDMS matrix (o-PDMS treatment) notably improves the fouling-prevention performance of the silicone elastomer. The o-PDMS treatment showed a marked improvement over the oil-free PDMS control in most of the field and lab experiments. However, the post-cure infusion approach (i-PDMS) shows a much stronger performance that exceeds the performance of the o-PDMS treatment at the same silicone oil concentration and Intersleek 700, an optimized and commercially relevant one-pot silicone foul-release (FR) treatment for marine applications. This is remarkable, as o-PDMS and i-PDMS tested in this study are essentially identical with regard to their composition. It is important to note that while the composition of both coatings is matching, their materials properties, such as stiffness or ability to form a lubricating liquid overlayer (LOL), are not.

[0393] It can hence be concluded that while both the oil incorporation approach (o-PDMS treatment) and the post-cure infusion approach (i-PDMS treatment) improve upon the fouling prevent! on/rel ease performance of silicone elastomers, the post-cure infusion approach leads to coatings with distinctly different properties and ability to combat fouling to a significantly greater degree. The explanation for this unique performance was provided by the mechanistic model describing o-PDMS and i-PDMS based on the Flory-Rehner theory of swelling an elastomer network in a small molecule solvent. The model suggests that for the two polymerization conditions, both with the same number of polymerizable monomers m and crosslinking molecules v, o-PDMS has a smaller value of N due to the lower density of effective crosslinks, which leads to longer chains and thus fewer chains per volume. As a result, o-PDMS with the same number of polymerizable monomers m and crosslinking molecules v will have significantly lower elastic modulus than i-PDMS, due to the linear relationship between shear modulus and crosslinking density. This prediction matches well with our observed shear moduli of 555 kPa and 1342 kPa for o-PDMS and i-PDM,S respectively (Fig. 5 A). The lower elastic modulus of o-PDMS may explain some of its enhanced antifouling performance and reduced adhesion strength of fouling organisms compared to neat, oil-free PDMS (Figs. 6A-6D, 7A-7D, 8), as it has been shown that the shear stress needed T to de-adhere a foulant from a soft elastic surface scales as r ~ is the work of adhesion. However, the improved performance of i-PDMS, which is 2.4 times stiffer than o-PDMS (FIG. 5 A), cannot be explained completely with this logic.

[0394] While some of the barnacle adhesion strength difference between i-PDMS and o- PDMS (FIGS. 6D, 9A-9B, 11 A-l IB, 12) could also be due to the swelling-induced thickness differences (~ 100 pm for the o-PDMS coating vs. - 150 pm for the i-PDMS coating), with thicker coating requiring less force to detach adhered barnacles, the difference in thickness is too small to explain the magnitude of the differences in de-adhesion forces.

[0395] Instead, the improved performance of i-PDMS is likely explained by the formation of a thin stable lubricating liquid overlayer (LOL) on its surface. While both experimental (FIG. 5C) and theoretical analyses show that a LOL does not form on o-PDMS at the same silicone oil concentration when not under a stress. This LOL could help to mitigate fouling in multiple ways. First, the lubricating liquid overlayer could mask the surface, preventing fouling organisms from recognizing it as a suitable solid substrate. The lubricating liquid overlayer also increases surface slipperiness, minimizing the force / weight required to release attached fouling organisms. Additionally, the LOL is likely responsible for the strong biofilm retraction forces seen in the C. lytica bacterial assay (FIG. 6A) and the Scituate field study (FIG. 8). This strong retraction force could disrupt early fouling community formation with the potential of delaying the fouling process by several months, as seen in Scituate (FIGS. 7A-7D) and Morro Bay (FIGS. 10A-10D) field immersion studies. Additionally, the removal and compression of the biofilm could reduce local settlement cues that would otherwise entice the larval stages of marine fouling organisms to adhere to the coatings. The retraction effects observed in the field occurred during the air-water interface transition of the treatments during the field surveys and may have little relevance to permanently submerged surfaces. Nevertheless, strong retraction effects are considered to be a good proxy for the adhesion-prevention performance of FR surfaces In cases where an organism is able to bypass the LOL and settle onto the PDMS surface, such as barnacle adhesion (FIGS. 6C-6D), the LOL can significantly lower the work of adhesion by leading to the formation of a lower-energy PDMS-oil interface upon de-adhesion, rather than the higher-energy PDMS-water interface that is created on surfaces without a LOL. This demonstrates repellent properties of slippery surfaces even in a partially de-wetted state.

-n - [0396] This raises the question of why o-PDMS coatings in these examples do not form a LOL despite having the same oil content as i-PDMS. The answer is again provided by the Flory-Rehner theory of elastomer swelling, in which the free energy decrease due to infiltration of solvent into the elastomer matrix is counteracted by the free energy cost of stretching the polymer chains. Thus, in o-PDMS, where the elastomer is polymerized in a stress-free state, more oil can be incorporated after polymerization before reaching saturation, while the infusion process leads to complete saturation of i-PDMS. The corresponding energy cost to remove oil from the PDMS matrix, the chemical potential p, is thus essentially zero in i-PDMS, leading to the facile formation of a LOL, while in o-PDMS p is high enough to maintain the oil in the bulk of the polymer and inhibit its travel to the interface to form a LOL (FIG. 3D). The long-term performance of i-PDMS is, therefore, likely determined by its ability to form and retain a LOL. The thermodynamic estimations provided above suggest that i-PDMS would need to lose about 20% of its oil loading to have a p value comparable to o-PDMS. While fouling release events and shear stresses may remove some lubricating liquid from the surface, this lubricating liquid is quickly replenished and total losses do not approach this 20% threshold. A strong indication that this is the case is the extended longevity that i-PDMS has shown during the Scituate Harbor, Morro Bay and Singapore Harbor field studies (Figs. 7A-7D, 8, 9A-9B, 10A-10D, 11A-11B, and 13A-13D), maintaining full performance over the entire study period of six, nine and 24 months, respectively. This i-PDMS performance duration is remarkable for a simple experimental coating procedure, especially as i-PDMS exceeded the performance of the commercial FR coating Intersleek 700 during this period.

[0397] The identification of a critical p value for the formation of a LOL is necessary to assess the longevity of the i-PDMS holistically and to guide the optimal design of FR coatings (FRC). The Flory-Rehner theory indicates that the p of o-PDMS can be reduced to zero through the application of a compressive stress during polymerization, suggesting a facile laboratory method for conducting these experiments and a potential way to create controllable, on-demand FRCs using the simpler o-PDMS process. This allows for the application of o-PDMS as slippery coatings with tunable wettability. Furthermore, the extended fouling prevention performance of i-PDMS has so far been tested in static fouling conditions, which is a critically important aspect as most ship hull fouling occurs when vessels are static. [0398] The enhanced performance of i-PDMS compared to o-PDMS of the same composition is likely explained by the materials’ different abilities to form and retain a lubricating liquid overlayer, which is explained using the Flory-Rehner theory of the thermodynamics of elastomer swelling. This theory provides guidance for the future design and optimization of fouling release coatings (FRCs), such as the ability of o-PDMS to form a LOL under biaxial stress, or the optimization of FRC’s composition using fully- biodegradable oils or unique polymer-oil formulations for which the chemical potential is sufficiently low, indicating the low energy cost of removing oil from the matrix and its travel to the free interface to form LOL. The ease of adding and removing silicone oil from i- PDMS also makes it a highly versatile material for medical applications, such as the harvesting of cell sheets or the fouling prevention in catheter tubes and scalpel blades.

B. Formation of a lubricating liquid overlayer on o-PDMS

[0399] In the following examples, a system of one-pot PDMS (o-PDMS) with dispersed silicone oil was investigated to demonstrate formation of a lubricating liquid overlayer on compressed PDMS.

[0400] FIGS. 14A-14B show an experimental set up for application of compression to o- PDMS. Compressed o-PDMS was examined for lubricating liquid overlayer formation, o- PDMS samples were formed by using one-pot method using 10: 1 Sylgrardl84 with 50 wt% loading with lOcSt methyl-terminated silicone oil system. The as-prepared samples were 10 mm x 10 mm x 8.48 mm size. The samples were compressed by 20% of their shortest dimension to induce the formation of lubricating oil overlayer as predicted by the mechanistic model. FIG. 14A shows four samples of stress-free o-PDMS in relaxed state to be used as controls. FIG. 14B shows four o-PDMS samples left under compression of 20% for 3 days. [0401] FIGS. 15A-15D show wetting behavior of compressed o-PDMS (scale bar 1mm) from FIG. 14B. Traces of lubricating liquid were found under the o-PDMS samples, after 3 days of compression (at 20%). The presence of a lubricating oil overlayer was investigated by observing for imprints of a 10 pl droplet on the sample surface. First, as shown in FIG. 15 A, a water droplet was positioned on the surface of the compressed o-PDMS. Next, as shown in FIG. 15B, when the droplet was pulled along the surface once and displaced from the original position. As shown in FIG. 15C, the droplet was pulled along the surface for a second time. FIG. 15D shows the same image as FIG. 15C with different lighting and with droplet imprints on the lubricating liquid marked by a dotted line. The imprints shown in FIG. 15C are an artifact of the wetting ridge formed by the lubricating liquid lubricating liquid lubricating liquid lubricating liquid at the air-droplet interface. The imprints indicate formation of a lubricating liquid overlayer on the compressed o-PDMS surface.

[0402] FIGS. 16A-16C show wetting behavior of control o-PDMS that was not under compression (scale bar Im) from FIG. 14 A. FIG. 16A shows the initial position of a droplet. FIGS. 16B and 16C show the droplet pulled along the surface once and a second time, respectively. In contrast to the compressed o-PDMS, on the control o-PDMS surface, the water droplet resisted movement from its original position.

[0403] The water droplet results shown in FIGS. 15A-15D and 16A-16C indicate reduced friction/pinning of the water droplets on compressed o-PDMS compared to the control. Additionally, the water droplets left faint imprints on compressed o-PDMS but not on the control o-PDMS, indicating the presence of a thin lubricating liquid layer on compressed o- PDMS but not on control o-PDMS. This indicates facile and smooth droplet mobility due to formation of a lubricating liquid overlayer on compressed o-PDMS but not on control o- PDMS.

[0404] FIGS. 17A-17D show the effect of compression on lubricating liquid formation after compression 5 and 10 days of compression. Optical imaging of the surface of compressed o-PDMS and control o-PDMS was performed to investigate the presence of lubricating oil overlayer. The compressed o-PDMS sample was maintained at a mechanical compressive strain of 30% and observed after 5 days and 10 days. o-PDMS appears to be mechanically stable under 30% compression (no tearing or breaking observed). As shown in FIG. 17A, after 5 days under continuous compression, discrete oil “puddles” measuring approximately 100 pm in diameter were observed on the surface of the compressed o-PDMS. As shown in FIG. 17B, after 10 days of continuous compression, the discrete oil puddles were observed to coalesce into a continuous film. Dynamics of the oil overlayer formation can be tuned via polymer cross-linking density, lubricating liquid viscosity, system chemical potential, etc. On the other hand, as shown in FIGS. 17C-17D, no oil puddles or overlayer was observed for the control o-PDMS (i.e., under stress-free state) after 5 (FIG. 17C) or 10 days (FIG. 17D).

[0405] It will be appreciated that while one or more particular materials or steps have been shown and described for purposes of explanation, the materials or steps may be varied in certain respects, or materials or steps may be combined, while still obtaining the desired outcome. Additionally, modifications to the disclosed embodiment and the invention as claimed are possible and within the scope of this disclosed invention.