CAPACITIVE SENSORS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application, under 35 U.S.C. § 119, claims the benefit of U.S. Provisional Patent Application Serial No. 63/379,979 filed on October 18, 2022, and entitled “Anisotropic Materials Applications In Printed Flexible Capacitive Sensors,” the contents of which are hereby incorporated by reference herein.

FIELD OF THE DISCLOSURE

[0002] This disclosure relates generally to compliant sensor systems and methods for sensors that bend, flex, stretch, twist, or the like to measure, force, strain, stress, or the like. More particularly, this disclosure relates to compliant sensor systems and methods for sensors configured to have anisotropic movement behavior.

BACKGROUND

[0003] Flexible sensors are known. For example, U.S. Pat. Nos.: 8,941,392; 9,222,764; 9,476,692; 9,612,102; 9,874,431; 10,551,917; 10,823,546; 10,959,644, and U.S. Pat. App. Pub. 2022/0034692, the contents of which are hereby incorporated by reference herein, disclose flexible sensors. However, there may be a need to make defined, directional measurements or comparisons with flexible sensors. Existing flexible sensors typically exhibit isotropic response for a given range of flex or strain and typically provide a magnitude for a given measurement, but not a direction.

[0004] In theory, if the undesired axis dimension (i.e., the direction in which a measurement is not desired) is reduced to an infinitesimally small value, then the integral strain registered by the sensor should be dominantly from the desired axis (i.e., the direction in which a measurement is desired). In practice, this approach does not work due to, among other things, the high resistivity of the conductive layer of the sensor. Other drawbacks, inconveniences, inefficiencies, and issues also exist with current systems and methods.

SUMMARY

[0005] Accordingly, disclosed embodiments address the above, and other, drawbacks, inconveniences, inefficiencies, and issues that exist with current systems and methods. Other advantages and efficiencies of disclosed systems and methods also exist.

[0006] As used herein, “flexible,” “extensible,” “compliant,” “deformable,” and the like are used somewhat interchangeably and all mean that some amount of flexing, stretching, compression, twisting, bending, or the like, exists for the described embodiment.

[0007] As used herein, “undesired axis,” “restricted axis,” “unmeasured axis,” and the like all refer to the direction in which a sensor measurement or reading is not desired. Likewise, as used herein, “desired axis,” “unrestricted axis,” “measured axis,” and the like all refer to the direction in which a sensor measurement or reading is desired.

[0008] It should be understood that, as used herein, the terms “vertical,” “horizontal,” “lateral,” “upper,” “lower,” “top,” “bottom,” “left,” “right,” “inner,” “outer,” etc., can refer to relative directions or positions of features in the disclosed devices and/or assemblies shown in the Figures. For example, “upper” or “uppermost” can refer to a feature positioned closer to the top of a page than another feature. These terms, however, should be construed broadly to include devices and/or assemblies having other orientations, such as inverted or inclined orientations where top/bottom, over/under, above/below, up/down, and left/right can be interchanged depending on the orientation.

[0009] Disclosed exemplary embodiments include a compliant sensor having non-extensible fibers in parallel with the unmeasured axis. The fibers physically oppose the force induced by the deforming source until the breaking point of the fibers. In this manner signals from the restricted, unmeasured axis are filtered out leaving only measurements from the unrestricted axis. Other embodiments also exist. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. l is a schematic cross-sectional view of a stack of layers to form a compliant sensor system in accordance with disclosed embodiments.

[0011] FIG. 2 is a multi-region angular displacement sensor in accordance with disclosed embodiments.

[0012] FIG. 3 is a schematic example of a deformable isotropic printed flexible capacitive sensor system in accordance with disclosed embodiments.

[0013] FIG. 4 is a schematic example of a deformable anisotropic printed flexible capacitive sensor system in accordance with disclosed embodiments.

[0014] FIG. 5 is a schematic representation of an anisotropic sensor system with motion restrictors in the signal traces in accordance with disclosed embodiments.

[0015] FIG. 7 is a schematic representation of an anisotropic sensor system embedded in adhesive in accordance with disclosed embodiments.

[0016] FIGS. 6A and 6B are schematic illustrations of anisotropic sensor systems in accordance with disclosed embodiments.

[0017] While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

[0018] FIG. 1 is a schematic cross-sectional view of a stack 200 of layers to form a compliant sensor system. As shown, dielectric layer 12, is in between top electrode layer 2 and signal electrode layer 16. As also indicated schematically, perimeter electrode 140 electrically connects top electrode layer 2 and signal electrode layer 16. Other configurations are also possible.

[0019] In some embodiments, top electrode layer 2 may comprise an elastomeric layer (e.g., silicone) with conductive particles (e.g., nano-particles, such as carbon black, nickel nano- strands, silver nano-particles, graphene nano-platelets, graphene-oxides, or the like) integrated within. While shown in FIG. 2 as a continuous layer, top electrode layer 2 may also be “hatched” or otherwise non-continuous. Top electrode layer 2 may also include a printed circuit board (PCB) interface and a number of conductive trace pads for attaching a PCB, sensor traces, or other electronics, for operation and control of the sensor system.

[0020] In some embodiments dielectric layer 12 may comprise an elastomeric material (e.g., silicone) and, as desired, may have some conductive material integrated within depending upon, among other things, the intended amount of permittivity, or the like. While not drawn rigorously to scale in FIG. 1, in some embodiments dielectric layer 12 is sized to be slightly smaller than top electrode layer 2 to leave a perimeter edge of top electrode layer 2 uncovered by dielectric layer 12 and allow electrical contact with perimeter electrode 140 as disclosed below.

[0021] In some embodiments signal electrode layer 16 may comprise an elastomeric material (e.g., silicone) with conductive material (e.g., nano-particles, such as carbon black, nickel nano-strands, silver nano-particles, graphene nano-platelets, graphene-oxides, or the like) confined to sensor regions, traces, and perimeter electrode 140. A number of sensor regions 20 (labeled as “sensing region” in FIG. 3 and used herein interchangeably with “sensor region”) may be distributed throughout the layer 116 (see, e.g., FIG. 3). Sensor regions 20 may comprise regions of electrically conductive material. Sensor regions 20 are electrically in communication with traces 22 (labeled as “signal trace line” in FIG. 3 and used herein interchangeably with “trace” and “traces”) that are printed with signal electrode layer 16. As shown, embodiments of signal electrode layer 16 may include a perimeter electrode 140 that electrically connects to top electrode layer 2 to, among other things, provide electrical isolation for the entire sensor system. Other configurations are also possible.

[0022] FIG. 2 is a multi-region angular displacement sensor 800 in accordance with disclosed embodiments. As shown, embodiments of the sensor system 200 as disclosed in FIG. 1, may be coupled together to form an angular displacement sensor 800. For example, by coupling sensor system 200A through an elastomeric connector 802 to a second sensor system 200B an angular displacement sensor 800 (single region, multi-region, or the like) may be implemented. Additional disclosure of the construction, operation, and implementation of such displacement sensor systems 800 may be found in U.S. Pat. No. 10,551,917, titled “Compliant Multi-Region Angular Displacement And Strain Sensors,” and the disclosure ofwhich is hereby incorporated by reference in its entirety.

[0023] As persons of ordinary skill in the art having the benefit of this disclosure would understand, the angular displacement sensor 800 can be extended to as many regions as desired as indicated by additional elastomeric connectors 802 and sensor systems 200N. Other configurations are also possible.

[0024] FIG. 3 is a schematic example of a deformable isotropic printed flexible capacitive sensor system 300 in accordance with disclosed embodiments. As shown, at least one sensing region 20 may be included in an elastomeric material and provided with one or more signal traces 22 for electronic communication with other system circuitry and components. Other configurations are possible.

[0025] FIG. 4 is a schematic example of a deformable anisotropic printed flexible capacitive sensor system 400 in accordance with disclosed embodiments. As shown, anisotropic sensor system 400 comprises motion restrictors 24 in the sensing region 20 that restrict or otherwise impede flexing or extension along the restricted axis direction. In some embodiments the motion restrictors 24 may comprise carbon fibers, poly-paraphenylene terephthalamide (e.g., Kevlar®) fibers, woven fibers, fiberglass, inextensible films, epoxies, or the like. Additionally, motion restrictors 24 may be electrically conducting or non-conducting as desired.

[0026] As indicated schematically on FIG. 4, the anisotropic sensor system 400 enables flex or extension measurements in the “vertical” (top to bottom on the page) direction and restricts flex or extension measurements “horizontally” (left to right on the page). In general, the motion restrictors 24 can be printed, attached, or otherwise included in the sensor 400 in parallel to the preferred direction of restriction to enable flex or extension measurements in the perpendicular direction to the alignment of the motion restrictors 24. Of course, those of ordinary skill in the art having the benefit of this disclosure would understand that any direction of measurement may be implemented by the appropriate inclusion or absence of motion restrictors 24. For example, and with reference to FIG. 4, a “diagonal” pattern of motion restrictors 24 would enable flex or extension measurements at a 45-degree (or other angle) direction (e.g., bottom left corner to top right corner on the page). Additionally, motion restrictors 24 may be oriented in more than one axis (e.g., a crosshatched pattern) to prevent flex or extension measurements in more than one direction at a time. Other embodiments are also possible. [0027] The spacing of motion restrictors 24 may also vary as desired. For example, the spacing may depend on smallest intended deforming body size. In general, the contact area between a deforming body and sensing region 20 should be bigger than the motion restrictor 24 spacing to ensure contact with at least one restrictor 24. Other embodiments are also possible.

[0028] FIG. 5 is a schematic representation of an anisotropic sensor system 500 with motion restrictors 24 in the signal traces 22 in accordance with disclosed embodiments. In some embodiments anisotropic restriction of signal traces 22 in deformable flexible sensors may be desirable to, among other things, mitigate the undesired effects of signals generated as a byproduct of signal trace 22 deformations. As shown, one or more signal traces 22 may be in electrical contact with sensing region 20. As shown in exploded portion “A”, motion restrictors 24 may be included for unidirectional restriction (top-to-bottom on page) and deformation in the perpendicular direction (left-to-right on page). In some embodiments, bidirectional restriction may be desirable as illustrated in exploded portion “B”, where motion restrictors 24A are provided in the one direction (left-to-right on page) and motion restrictors 24B are provided in a second direction (top-to-bottom on page) to restrict flex or extension in two directions simultaneously. In multi-direction restriction embodiments, motion restrictors 24 may be in a single layer, in multiple layers, in woven layers, or the like. Other configurations and embodiments are also possible.

[0029] FIGS. 6 A and 6B are schematic illustrations of anisotropic sensor systems 600A and 600B in accordance with disclosed embodiments. As illustrated schematically, motion restrictors 24 may be placed in any layer of the sensor systems. For example, as shown in FIG. 6A, motion restrictors 24 may be placed in conductive layer (e.g., signal layer 16) or, as shown in FIG. 6B, motion restrictors 24 may be placed in non-conductive layer (e.g., dielectric layer 12).

[0030] In general, motion restrictors 24 may be electrically conductive and coupled directly onto a defined electrode layer (e.g., top electrode 2, signal electrode 16, etc.). This has an added benefit of increased electrode conductivity if the motion restrictors 24 are more conductive than the electrode. Alternatively, for conductive motion restrictors 24 the signal layer 16 may be replaced by the conductive motion restrictors 24. Alternatively, the motion restrictors 24 may be coupled onto the conductive layer. When included in signal traces 22, if the motion restrictor24 resistivity is lower than the electrode layer resistivity, the signal trace 22 conductor losses will be lower. Other advantages and embodiments also exist.

[0031] FIG. 7 is a schematic representation of an anisotropic sensor system 700 embedded in adhesive 704 in accordance with disclosed embodiments. For example, an anisotropic element (e.g., carrier layer 706) having anisotropic motion restrictors 24 (not shown in FIG. 7) may be embedded in an adhesive (e.g., layers 704) used for bonding all or certain parts of the sensor system 700 to a target substrate (e.g., the inside of tire or the like). In some embodiments, a liner layer 702 may also be provided to, among other things, protect the outer adhesive layer 704. Other configurations and embodiments are also possible.

[0032] Although various embodiments have been shown and described, the present disclosure is not so limited and will be understood to include all such modifications and variations would be apparent to one skilled in the art.