ELECTRONIC DEVICE

TECHNICAL FIELD

[0001] Various aspects of this disclosure relate to a layered electronic device, and a method for producing the layered electronic device.

BACKGROUND

[0002] Conventional electronic devices may have electrically active layers between electrodes. The electrically active layers may include composite layers including high dielectric constant fillers to enhance the dielectric properties of the device. Such fillers however, cause a local intensification of an applied electric field due to the Maxwell-Wagner-Sillars (MWS) effect at the filler/matrix interface leading to severe degradation of electric breakdown strength, and premature breakdown of the device.

[0003] Therefore, there is a need to provide an improved layered electronic device which exhibits high electric breakdown strength.

SUMMARY

[0004] It is therefore, object of the invention to provide an improved layered electronic device, for example an electromechanical actuator.

[0005] Various embodiments may provide a layered electronic device. The layered electronic device may include a stack, which may further include a first and a second electroactive polymer (EAP) layers. Each of the first and second EAP layers may include an EAP material. A substantial portion thereof, may each be particle free. The stack may further include an electroactive composite layer which may be disposed in between the first and second EAP layers and may include a thickness along a first direction. The electroactive composite layer may include a polymer matrix and may further include particles.

[0006] Various embodiments may provide a method for producing the layered electronic device. The method may include providing a substrate and forming the stack. The stack may include depositing a first EAP layer material, depositing an EAP composite layer composition, and may further include depositing a second EAP layer material.

[0007] According to various embodiments, the layered electronic device may be a flexible haptic feedback actuator. According to various embodiments, the layered electronic device may be a thin film flexible haptic feedback actuator.

BRIEF DESCRIPTION OF THE DRAWINGS [0008] The invention will be better understood with reference to the detailed description when considered in conjunction with the non-limiting examples and the accompanying drawings, in which:

- FIGS. 1A and IB show schematic illustrations of a cross section of a layered electronic device 100, by way of example, in accordance with various embodiments;

- FIGS. 2A and 2B show schematic illustrations of layered electronic devices 200 and 230, by way of example, in accordance with various embodiments;

- FIG. 3 shows a schematic illustration of an exemplary method 300 for producing a layered electronic device 100, in accordance with various embodiments;

- FIG. 4 shows a scanning electron microscope (SEM) image of the cross section of the EAP / ZrChiEAP / EAP layers, by way of example, in accordance with various embodiments;

- FIGS. 5A and 5B show the X-ray diffraction (XRD) spectra comparing the (A) EAP / ZrC>2 layers and the EAP / ZrChiEAP / EAP layers, and (B) the EAP / T1O2 layers and the EAP / TiC^EAP / EAP layers, by way of example, in accordance with various embodiments;

- FIGS. 6A to 6C show the electric breakdown distribution and ferroelectric hysteresis graph of the EAP / ZrChiEAP / EAP layers, as compared to the EAP / ZrC>2 layers, by way of example, in accordance with various embodiments;

- FIGS. 7A to 7C show the electric breakdown distribution and ferroelectric hysteresis graph of the EAP / TiC^EAP / EAP layers, as compared to the EAP / T1O2 layers, by way of example, in accordance with various embodiments; and

- FIG. 8 shows a graph comparing the output force of the EAP / ZrChiEAP / EAP layers, the EAP / TiC^EAP / EAP layers and the neat EAP / EAP / EAP layers, by way of example, in accordance with various embodiments.

DETAILED DESCRIPTION

[0009] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure. Other embodiments may be utilized and structural, and logical changes may be made without departing from the scope of the disclosure. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. [0010] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and/or combinations and/or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0011] The disclosure illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Thus, for example, the terms “comprising”, “including,” containing”, etc. shall be read expansively and without limitation. The word "comprise" or variations such as "comprises" or "comprising" will accordingly be understood to imply the inclusion of a stated integer or groups of integers but not the exclusion of any other integer or group of integers. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the disclosure. Thus, it should be understood that although the present disclosure has been specifically disclosed by exemplary embodiments and optional features, modification and variation of the disclosure embodied herein may be resorted to by those skilled in the art.

[0012] In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

[0013] The reference signs included in parenthesis in the claims are for ease of understanding of the disclosure and have no limiting effect on the scope of the claims.

[0014] As used therein, and in accordance with various embodiments, the “/” may mean a layer separation, for example, “A / B” may mean that components A and B are in separate layers, such as, e.g., a major surface of layer A facing a major surface of layer B, layers A and B are on top of each other, layers A and B overlapping each other directly or indirectly with further layers in between. As used therein, and in accordance with various embodiments, the may mean that the components of a layer for a mixture or blend, for example, “A : B” may mean that A and B are mixed or blended in a common layer.

[0015] According to various embodiments, the term “layered”, as used herein, may refer to an arrangement of layers or sheets, stacked one on top of the other. The term layered may include two or more layers arranged in a multi-stack structure. For example, the term layered may refer to the arrangement including a first electroactive polymer (EAP) layer, an electroactive composite layer stacked on top the first EAP layer, and a second EAP layer stacked on top of the electroactive composite layer. Accordingly, the term “layered electronic device” may refer to an electronic device that may be formed by the arrangement of layers. As used herein and in accordance with various embodiments, the terms “top” and “bottom” are used to indicate different sides, and may further indicate a position or stacking direction in relation to the substrate or to ground, for example, the substrate being closer to the bottom than the electroactive layers, which may be “on top” of the substrate.

[0016] According to various embodiments, the term “particle(s)”, as used herein, may refer to discrete piece(s), which may be composed of ceramic or metallic materials. For example, ceramic particles may be inorganic and may further be heat-resistant, and may be made of both metallic and non-metallic compounds. Metallic particles may comprise metallic elements. The ceramic particles and the metallic particles may exhibit one or more of dielectric, ferroelectric, piezoelectric properties, in accordance with various embodiments. Within the context of the disclosure, some embodiments and examples may use ceramic particles. It is nevertheless envisioned that the embodiments and examples according to the disclosure may use metallic particles instead (or in addition to) ceramic particles.

[0017] FIG. 1A shows a schematic illustration of a cross section of a layered electronic device 100, by way of example. The inset shows an enlarged view of a portion of the electroactive composite layer 130, in accordance with various embodiments. The layered electronic device 100 may include a substrate 110 and a stack 170. The stack 170 may include a first EAP layer 120, an electroactive composite layer 130 and a second EAP layer 140. The electroactive composite layer 130 may be disposed between the first and second EAP layer 120, 140, and may include a thickness along a first direction ID. The first direction ID may be perpendicular to the substrate 110, in accordance with various embodiments. The electroactive composite layer 130 may be aligned parallel to the substrate 110. The electroactive composite layer 130 may be sandwiched in between the first and second EAP layers 120, 140. The layered electronic device 100 may further include a first electrode 180 and a second electrode 190 and the stack 170 disposed between the first electrode 180 and the second electrode 190. For example, the stack 170 may be sandwiched between the first and second electrodes 180, 190. Thereby, the first EAP layer 120 may be in contact with the first electrode 180 and the second EAP layer 140 may be in contact with the second electrode 190. Within the context of the present disclosure and in accordance with various embodiments, the layered electronic device 100 may be an electromechanical device, for example, a haptic feedback actuator. As a further example, the layered electronic device 100 may be a flexible haptic feedback actuator. [0018] According to various embodiments, the substrate 110 may include any substrate which may be suitable for use in actuators. For example, the substrate 110 may be a flexible substrate and/or a transparent substrate. As a further example, the substrate 110 may be a polymer substrate, for instance, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), which may be flexible and/or transparent.

[0019] The first and second EAP layers 120, 140 may each include an EAP material. A substantial portion thereof each of the first and second EAP layers 120, 140 may be particle 160 (e.g. ceramic particle) free.

[0020] According to various embodiments, the term “electroactive polymer” or its abbreviation EAP, as used herein, may refer to a polymer which may undergo a shape change in response to an applied electrical field, which polymer may further emit an electrical signal upon mechanical stimulation. The electrical signal may be detected via electrodes coupled to the EAP. The EAP may be a type of electroactive material. Within the context of the present disclosure and in accordance with various embodiments, the EAP is a polymer that undergoes shape change in response to an applied electrical field. Examples of EAPs may include: dielectric EAP (dEAP), piezo electric active polymer (piezoEAP). Examples of piezoEAPs include poly (vinylidenefluoride) abbreviated as (PVDF) and its copolymers, namely: ferroelectric EAPs (ferroEAPs) such as poly (vinylidenefluoride - trifluoroethylene - chlorotrifluoroethylene) abbreviated as P(VDF - TrFE - CTFE), poly (vinylidenefluoride- trifluoroethylene - chlorofluoroethylene) abbreviated as P(VDF - TrFE - CFE), poly (vinylidenefluoride - trifluoroethylene - hexafluoropropylene) abbreviated as P(VDF - TrFE - HFP), and poly[(vinylidenefluoride - co - trifluoroethylene] abbreviated as P(VDF - TrFE), poly[ (vinylidenefluoride - co - hexafluoropropylene] abbreviated as P(VDF - HFP), poly[ (vinylidenefluoride - co - chlorotrifluoroethylene] abbreviated as P(VDF - CTFE). Examples of dielectric EAPs are: acrylic elastomers, silicon elastomers, fluoroelastomers, polyurethane, natural/synthetic rubbers.

[0021] According to various embodiments, the term “EAP material”, as used herein, may refer to a material including EAPs as defined above. For example, an EAP material may include an EAP composition, of which includes at least one EAP. In accordance with various embodiments, the term EAP material may include or be, an EAP.

[0022] According to various embodiments, the term “substantial portion thereof, as used herein, with respect to a layer, may mean that a large proportion of the layer comprises or consists essentially of a material, for example, the EAP. In other words, said layer may not contain, or may contain small amounts of an impurity, for example, inorganic particles such as ceramic particle(s). For example, the term substantial portion thereof may mean that the proportion of EAP in the layer comprises more than 95 %, or more than 98 % of the thickness of said layer, or the layer is particle free.

[0023] According to various embodiments, the term “particle free”, as used herein, may refer to the EAP material, for example, an EAP composition including an EAP, which may not include particles (e.g. ceramic particles), or may include trace or minute amounts of particles (e.g. ceramic particles). For example, minute amounts of the particles (e.g. ceramic particles) may inadvertently be lodged in the EAP material of the adjacent EAP layers (e.g. first and second EAP layers), due to the diffusion of the particles (e.g. ceramic particles) from the electroactive composite layer (e.g. during the formation of the layered electronic device). The term particle (e.g. ceramic particles) free may refer to an EAP material including 96 vol% to 100 vol% of the EAP (e.g. < 5 vol% of the particles, for example, ceramic particles). For example, the term particle (e.g. ceramic particles) free may refer to an EAP material of 98 vol% to 100 vol% of the EAP (e.g. < 2 vol% of the particles, for example, ceramic particles). Within the context of the present disclosure and in accordance with various embodiments, the term particle (e.g. ceramic particles) free may refer to the EAP material including < 2 vol% of particles (e.g. ceramic particles). In other words, the EAP material of the first and second EAP layers 120, 140 may include at least 98 vol% of the EAP.

[0024] According to various embodiments, the EAP material of the first and second EAP layer 120, 140, may include an EAP composition including an electroactive material, for example, an EAP. As a further example, the EAP material may include ferroEAPs such as PVDF - TrFE, P(VDF - TrFE - CTFE), P(VDF - TrFE - CFE). According to a preferred embodiment, the EAP material of the first and second EAP layers 120, 140 may be P(VDF - TrFE - CTFE).

[0025] In FIG. 1A, the inset shows an enlarged view of an exemplary schematic illustration of the electroactive composite layer 130 in accordance with various embodiments. The electroactive composite layer 130 may include a polymer matrix 150 and particles 160 (e.g. ceramic particles). For example, the electroactive composite layer 130 may include particles 160 (e.g. ceramic particles) dispersed within the polymer matrix 150. As a further example, the polymer matrix 150 may be a mass in which the particles 160 (e.g. ceramic particles) are embedded in. The particles 160 (e.g. ceramic particles) may include particles with a high dielectric constant (e.g. higher than the dielectric constant of silicon dioxide, e.g., > 3.9) to enhance the permittivity and polarizability of the electroactive composite layer 130. For example, the particles 160 may be ceramic particles and may include dielectric ceramic nanoparticles. While the particles 160 (e.g. ceramic particles) illustrated in FIGS. 1A and IB are of different dimensions, in some embodiments, the particles 160 may be of a regular size and/or shape. For example, each particle 160 (e.g. ceramic particle) may be substantial identical with a narrow size distribution.

[0026] According to various embodiments, the polymer matrix 150 may be a matrix including an electroactive material, for example, an EAP. As a further example, the polymer matrix 150 may include ferroEAPs, for instance, PVDF - TrFE, P(VDF - TrFE - CTFE), P(VDF - TrFE - CFE). According to a preferred embodiment, the polymer matrix 150 may include the P(VDF - TrFE - CTFE) EAP. The first (120) and second (140) EAP layers and the polymer matrix (150) of the electroactive composite layer (130) may include the same EAP material as its main constituent, in accordance with various embodiments. For example, said same EAP material may be the P(VDF - TrFE - CTFE) EAP.

[0027] According to various embodiments, the particles 160 (e.g. ceramic particles) may be in a nanometer range (e.g. scale) of dimensions. The size, for instance, the diameter of the particles 160 (e.g. ceramic particles) may, for example, include dimensions in the range of 2 nm to 300 nm. For example, the size (e.g. diameter) of the particles 160 (e.g. ceramic particles) may be in the range of 2 nm to 200 nm. Within the context of the present disclosure, the particles 160 (e.g. ceramic particles) may include nanoparticles 160 (e.g. ceramic nanoparticles) with a size (e.g. diameter) range of 2 nm to 100 nm.

[0028] According to various embodiments, the particles 160 may include or be ceramic particles. The ceramic particles 160 may include a metal oxide. The metal oxide may include particles including a metal cation and an oxide anion. The metal oxide may be of a high dielectric constant and may be a piezoelectric metal oxide. Thus, the particles 160 may generate an electric current in response to applied mechanical stress. Examples of metal oxides include, zirconium dioxide abbreviated as (ZrCh), titanium dioxide abbreviated as (T1O2), barium titanate abbreviated as (BaTiOs), barium strontium titanate abbreviated as ((Ba Sr)TiOs), magnesium titanium oxide abbreviated as (MgTiOs), calcium copper titanate abbreviated as (CaCusTUO^), lead magnesium niobate-lead titanate abbreviated as (Pb(Mgi/3Nb2/3)03), lead zirconate titanate abbreviated as (Pb(Zr,Ti)03). The ceramic particles 160 may be ZrC>2, or may be T1O2, in accordance with various embodiments.

[0029] According to various embodiments, the weight ratio of the particles 160 (e.g. ceramic particles) to the polymer matrix 150 of the electroactive composite layer 130 may be between 2 vol% to 70 vol%. For example, the weight ratio of the ceramic particles 160 to the polymer matrix 150 may be between 2 vol% to 60 vol%, or may be between 2 vol% to 50 vol%. [0030] According to various embodiments, the particles 160 (e.g. ceramic particles) in the electroactive composite layer 130 may be randomly dispersed within the polymer matrix 150, for example, in a second direction 2D which may be perpendicular to the first direction ID. The second direction 2D may, for example, be parallel to the substrate 110. For example, the particles 160 (e.g. ceramic particles) may be arranged in a non-uniform or irregular manner within the polymer matrix 150, along the second direction 2D within the polymer matrix 150 of the electroactive composite layer 130. As a further example, each particle 160 (e.g. ceramic particles) within the polymer matrix 150 may be located at different planes along the thickness of the electroactive composite layer 130 (e.g. along the first direction ID, perpendicular to the substrate 110). To illustrate, a first particle 160 may not be aligned with a second particle 160, within the polymer matrix 150. In other words, the particles 160 may not be dispersed in a regular array within the polymer matrix 150. In accordance with various embodiments, the particles 160 may include or be ceramic particles 160.

[0031] FIG. IB shows a schematic illustration of a cross section of the layered electronic device 100, by way of example. The insets (a) and (b) show enlarged views of regions of the electroactive composite layer 130, in accordance with various embodiments. According to various embodiments, a concentration of particles 160 (e.g. ceramic particles) in the electroactive composite layer 130 in a first region may be different to a concentration of particles 160 (e.g. ceramic particles) in the electroactive composite layer 130 in a second region, within the polymer matrix 150. The first and second regions may be along the second direction 2D (e.g. parallel to the substrate 110). The first and second regions may include a thickness along the first direction ID of the electroactive composite layer 130, and may be distant to the substrate 110. In FIG. IB, inset (a) shows an enlarged view of the schematic illustration of an exemplary first region in the electroactive composite layer 130. Inset (b) shows an enlarged view of the schematic illustration of an exemplary second region in the electroactive composite layer 130. The first region (e.g. inset (a)) may include a larger number of particles 160 (e.g. ceramic particles) dispersed within the polymer matrix 150, when compared to the second region (e.g. inset (b)). In other words, the concentration of particles 160 (e.g. ceramic particles) in the first region of the electroactive composite layer 130 may be higher than the concentration of particles 160 (e.g. ceramic particles) in the second region (e.g. inset (b)), within the polymer matrix 150. To put it another way, the concentration of particles 160 (e.g. ceramic particles) in the second region may be lower than that in the first region, within the polymer matrix 150 of the electroactive composite layer 130. For example, the difference between the concentration of particles 160 (e.g. ceramic particles) between the first and second regions may be less than 20 %, less than 10% or less than 5 %. Alternatively, the concentration of particles 160 (e.g. ceramic particles) within the polymer matrix 150 of the electroactive composite layer 130 may be substantially uniform, in accordance with various embodiments. For example, the concentration of particles 160 (e.g. ceramic particles) of the first and second regions may be equal.

[0032] According to various embodiments, the thickness of the electroactive composite layer 130 may be less than 10 pm, less than 5 pm or less than 2 pm. Thus, the size (e.g. diameter) of the particles 160 (e.g. ceramic particles in the range of 2 nm to 100 nm) may include or be, less than half, less than 10 %, less than 5 % or less than 1 % of the thickness of the electroactive composite layer 130.

[0033] According to various embodiments, the thickness of the stack 170 may be less than 300 pm, less than 200 pm or less than 100 pm. For example, the thickness of the stack 170 may be between 2 pm to 100 pm, or between 2 pm to 50 pm. Thus, the thickness of the layered electronic device 100 as a whole may include a thickness which may be suitable for electromechanical applications, for example, thin film electromechanical applications (e.g. for use in thin film flexible haptic feedback actuators). According to various embodiments, the thickness of the layered electronic device 100 may be less than 800 pm, or less than 500 pm, and may include the substrate 110, the stack 170, and the first and second electrodes 180, 190.

[0034] FIG. 2A shows a schematic illustration of a layered electronic device 200, by way of example, in accordance with one embodiment. The layered electronic device 200 may include a substrate 210 and a plurality of the stack 220 arranged as an array. The substrate 210 may be a common substrate 210 for each stack 170 of the plurality of the stack 220. The plurality of the stack 220 may include an individual stack 170. For example, the individual stack 170 may include the first and second EAP layers 120, 140 and the electroactive composite layer 130 sandwiched between the first and second EAP layers 120, 140. Individual stacks 170 of the plurality of the stack 220 may be arranged side-by-side in a direction parallel to a main surface of the common substrate 210, and may thus form the array. For example, each stack 170 of the plurality of the stack 220 may be arranged adjacent to each other and in a regular array along a plane which is parallel to the main surface of the common substrate 210. As a further example, each stack 170 of the plurality of the stack 220 may be in contact with each other (e.g. parallel to the surface of the plurality of the stack 220). For example, the first 120 and second 140 EAP layers, and the electroactive composite layer 130 of a first stack 170 of the plurality of the stack 220 may be in contact with that of a second stack 170 of the plurality of the stack 220. The layered electronic device 200 may further include electrodes, and the plurality of the stack 220 may be arranged between the electrodes.

[0035] FIG. 2B shows a schematic illustration of a layered electronic device 230, by way of example, in accordance with another embodiment. The layered electronic device 230 may include a substrate 240 and a plurality of the stack 250 arranged as a superstack. For example, the substrate 240 may be a common substrate 240 for the plurality of the stack 250. The plurality of the stack 250 may include an individual stack 170. For example, the individual stack 170 may include the first and second EAP layers 120, 140 and the electroactive composite layer 130. Individual stacks 170 of the plurality of the stack 250 may be arranged in a multi- stacked arrangement (e.g. superstack). For example, each stack 170 of the plurality of the stack 250 may be stacked in a direction perpendicular to the main surface of the common substrate 240, and may be stacked one on top of the other in a regular array. To illustrate, a second stack may be arranged on top of a first stack, and a third stack may be arranged on top of the second stack, such that the plurality of the stack 250 forms a multi-stacked structure. As a further example, each stack 170 of the plurality of the stack 250 may be in contact with each other (e.g. in the direction perpendicular to the main surface of the common substrate 240). For example, the second EAP layer 140 of a first stack 170 of the plurality of the stack 250 may be in contact with the first EAP layer 120 of a second stack 170 of the plurality of the stack 250. Alternatively, a single EAP layer, for example, between two individual stacks 170 of the superstack 250, may replace the second EAP layer 140 of the first stack 170 of the plurality of the stack 250 and the of first EAP layer 120 of the second stack 170 of the plurality of the stack 250 (which are in contact with each other). The layered electronic device 230 may further include electrodes, and the plurality of the stack 250 may be arranged between the electrodes (not shown in FIG. 2B).

[0036] The arrangements shown in FIGS. 2A and 2B merely serve as examples, and other embodiments may be envisioned (e.g. layered electronic device including both the array of stacks 220 and the superstack 250). Thus, there may be flexibility in producing various complex actuator designs according to the layered electronic device 100 of the present disclosure.

[0037] The detailed description of the production procedure is shown in connection with FIG. 3, which shows a schematic illustration of an exemplary method 300 for producing a layered electronic device 100 in accordance with various embodiments. The method 300 may include a step of providing the substrate 110 and the first electrode 180.

[0038] Step 310 includes the depositing of a first EAP layer 120 material. The first EAP layer 120 material may be deposited on the underlying substrate 110, or the underlying electrode, for example, the first electrode 180 (e.g. in a device). In accordance with various embodiments, the first EAP layer 120 material may include an EAP composition including an EAP. The first EAP layer 120 material may be deposited, for example coated, using, for example, doctor blade, rod coating, bar coating, screen printing, slot die coating, spin coating, roll to roll (R2R) coating, or another coating technique. FIG. 3 illustrates by way of example, rod coating, with rod 160. The first EAP layer 120 may further be patterned or non-patterned in accordance with various embodiments.

[0039] Step 310 may further include a post-process step wherein the first EAP layer 120 material is dried to remove the solvent and/or annealed. Annealing may reinforce the crystalline structure, and may further reinforce the ferroelectric properties of FerroEAPs. Vacuum and/or heat may be applied to facilitate the post-process step.

[0040] Step 320 includes the depositing of an electroactive composite layer 130 composition. The electroactive composite layer 130 composition may include the particles 160 (e.g. ceramic particles) dispersed within the polymer matrix 150, and may be deposited on the first EAP layer 120. The electroactive composite layer 130 composition may be deposited, for example coated, using any conventional layer coating techniques as described in step 310 above. The electroactive composite layer 130 composition may also be deposited, for example, using a polymer thin film transfer technique. Said technique may include fabricating the electroactive composite layer 130 as a thin film multi-up on a reusable temporary glass carrier and later transferring the electroactive composite layer 130 onto a layer of choice, for example, the underlying first EAP layer 120.

[0041] According to various embodiments, the electroactive composite layer 130 composition including the polymer matrix 150 and the particles 160 (e.g. ceramic particles) may be a solution. For example, the polymer matrix 150 and the particles 160 (e.g. ceramic particles) may be suspended in the solution. The solution may include a solvent, which may be chosen to dissolve the EAP of the polymer matrix 150 and to disperse and prevent agglomeration of the particles 160 (e.g. ceramic particles). Further, the solvent of choice may avoid dissolving the underneath layer (e.g. first EAP layer 120) and/or destroying the crystallinity achieved by a previous annealing process at step 310. For example, solvents for dissolving PVDF and its co- and terpolymers include but are not limited to methyl ethyl ketone abbreviated as (MEK), acetone, methyl iso-butyl ketone, cyclohexanone.

[0042] In the example of step 320 of FIG. 3, Meyer rod coating may be adopted for depositing the electroactive composite layer 130 composition due to its fast speed and ease of use. However, other suitable coating techniques may be used, for example, bar coating, spray coating, screen printing and others. Rod 160 may be the same or different from the one used in step 310. The electroactive composite layer 130 may further be patterned or non- patterned in accordance with various embodiments.

[0043] Step 320 may further include a post-process step wherein the electroactive composite layer 130 composition is dried to remove the solvent and/or annealed, as described in step 310 above.

[0044] Step 330 includes the depositing of a second EAP layer 140 material, which may be deposited on the underlying layer for example, the electroactive composite layer 130. In accordance with various embodiments, the second EAP layer 140 material may include an EAP composition including an EAP. The second EAP layer 140 material may be deposited, for example coated, using any suitable layer coating techniques, or may be deposited using the polymer thin film transfer technique, as described in steps 310 and 320, respectively. Step 330 may further include a post-processing step wherein the second EAP layer 140 material is dried to remove the solvent and/or annealed, as described in step 310 above. The second EAP layer 120 may further be patterned or non-patterned in accordance with various embodiments.

[0045] Step 340 includes the treatment of the stack 170 including the first and second EAP layers 120, 140 and the electroactive composite layer 130. The treatment may include any conventional heat treatment and/or stretching treatment to improver polymer crystallinity and consequently, the dielectric properties of the layered electronic device 100. For example, step 340 may include heat treatment at 110 °C for 120 min.

[0046] Step 350 of FIG. 3 shows the layered electronic device 100 produced in accordance with various embodiments. Step 350 may include providing a second electrode 190 on the underlying layer, for example, the second EAP layer 140. The second electrode 190 may be deposited using any suitable layer coating techniques for example, sputtering, vapor deposition, or techniques as described in step 310 above. The first electrode 180 may also be deposited using one of these techniques, and may be in a similar manner as the second electrode. The first and second electrodes 180, 190 may be deposited independently from each other, and may each be patterned or non-patterned. According to various embodiments, the layered electronic device may include the substrate 110, the first and second EAP layers 120, 140, the electroactive composite layer 130, and the first and second electrodes 180, 190. [0047] According to various embodiments, the method 300 may further include forming an encapsulation. For example, a protective insulation layer may be coated on top of the topmost electrode (e.g. second electrode 190) for protection, for example for electrically insulating the layered electronic device 100 from a user touching the device.

Examples

[0048] In the Examples below, the particles 160 are referred to as ceramic particles 160. Nevertheless, it may be envisioned that the particles 160 may include or be, metallic particles. [0049] FIG. 4 shows a scanning electron microscope (SEM) image of the cross-section of the exemplary EAP / ZrC^iEAP / EAP layers (e.g. stack 170 in FIG. 1A, including the first 120 and second 140 EAP layers, and the electroactive composite layer 130 sandwiched between the first 120 and second 140 EAP layers). The first 120 and second 140 EAP layers and the electroactive composite layer 130 may include the EAP, P(VDF - TrFE - CTFE). The concentration of ceramic particles 160, ZrC>2, may be at a weight ratio of 50 vol%, and the scale bar represents 1 micrometer. As can be seen in FIG. 4, the electroactive composite layer 130 is clearly distinguishable from the first 120 and second 140 EAP layers, and shows reasonable sharp boundaries.

[0050] FIGS. 5 to 8 provide comparative examples of the EAP / ZrC>2 or EAP / T1O2 layers as compared to the EAP / ZrC^iEAP / EAP or EAP / TiC^iEAP / EAP (e.g. stack 170) layers. The EAP / ZrC>2 or EAP / T1O2 layers may include an EAP layer, for example, the first EAP layer 120, and the electroactive composite layer 130. In the electroactive composite layer 130 of the EAP / ZrC>2 or the EAP / T1O2 layers, the weight ratio of the ceramic particles 160 to the polymer matrix 150 may range between 10 vol% to 50 vol%. On the other hand, the EAP / Zr0 ₂ :EAP / EAP or the EAP / Ti0 ₂ :EAP / EAP layers may include the electroactive composite layer 130 sandwiched in between two EAP layers, for example, the first and second EAP layers 120, 140 (e.g. stack 170 in FIG. 1A). In the electroactive composite layer 130 of the EAP / Zr0 ₂ :EAP / EAP or the EAP / Ti0 ₂ :EAP / EAP layers, the weight ratio of the ceramic particles 160 to the polymer matrix 150 may be 50 vol%. The first and second EAP layers 120, 140, and the electroactive composite layer 130 may each include EAP, P(VDF - TrFE - CTFE). In the examples below, solvent MEK was used in the fabrication process (e.g. method 300 in FIG. 3).

[0051] FIG. 5 shows exemplary X-ray diffraction (XRD) spectrum of the: (A) EAP / ZrC>2 layers and the EAP / ZrC^iEAP / EAP layers, and (B) EAP / T1O2 layers and the EAP / TiChiEAP / EAP layers. As shown in FIGS. 5A and 5B, the peak intensity of the EAP / ZrChiEAP / EAP or the EAP / TiChiEAP / EAP layers remain at 18.3° regardless of the type of ceramic particle 160 used. In FIG. 5A, the peak intensity using the ZrC>2 ceramic particle 160 (marked by an arrow) may be between that of the EAP / ZrC>2 layers including a 40 vol% (labelled as 510) to 50 vol% (labelled as 520) weight ratio of ZrC>2 to the polymer matrix 150. In FIG. 5B, the peak intensity using the T1O2 ceramic particle 160 (marked by an arrow) may be between that of the EAP / T1O2 layers including 30 vol% (labelled as 530) to 40 vol% (labelled as 540) weight ratio of T1O2 to the polymer matrix 150. From FIGS. 5A and 5B, it may be seen that the EAP / ZrChiEAP / EAP and the EAP / TiChiEAP / EAP layers exhibit higher crystallinity, as compared to the EAP / ZrC>2 and EAP / T1O2 layers, since the first and second EAP layers 120, 140 which are ceramic particle 160 free, may not hinder the formation of polymer crystallites in the electroactive composite layer 130 during the drying and annealing process (e.g. post-process step 320).

[0052] FIGS. 6A to 6C show the electric breakdown distribution and ferroelectric hysteresis graph of the EAP / ZrChiEAP / EAP layers, as compared to the EAP / ZrC>2 layers, by way of example. FIG. 6 shows the (A) Weibull distribution of electric breakdown; and the (B) polarization graph of the EAP / ZrC>2 and the EAP / ZrChiEAP / EAP layers at 75 V/pm. FIG. 6C provides the corresponding table of the electric breakdown strength EB, dissipation factor DF and polarization P, of the EAP / ZrC>2 and EAP / ZrC^EAP / EAP layers, obtained from the graphs of FIGS. 6A and 6B. From FIGS. 6A to 6C, it may be seen that the EAP / ZrC^EAP / EAP layers exhibits a significantly larger electric breakdown strength EB of 113.3 MV/m, as compared to the EAP / ZrC>2 layers at varying concentrations of ZrC>2. For example, the electric breakdown strength EB of the EAP / ZrC^EAP / EAP layers may be 143.1 % of the EAP / ZrC>2 layers with a ZrC>2 weight ratio of 40 vol%. With reference to FIG. 6B, the polarization P of the EAP / ZrC^EAP / EAP layers may be similar to that of the EAP / ZrC>2 layers with a weight ratio of 40 vol%, and may exhibit a slimmer hysteresis loop suggesting lower dielectric loss. Further, the EAP / ZrC^EAP / EAP layers exhibit a lower dissipation factor DF as compared to the EAP / ZrC>2 layers with a ZrC>2 weight ratio of 30 vol%. In other words, the EAP / ZrC^EAP / EAP layers exhibit increased electric breakdown strength EB and polarization P, with a lower dissipation factor DF and dielectric loss, when compared to the EAP / ZrC>2 layers with a ZrC>2 weight ratio of 40 vol% (indicated by arrows in FIG. 6C).

[0053] FIGS. 7A to 7C show the electric breakdown distribution and ferroelectric hysteresis graph of the EAP / TiC^iEAP / EAP layers, as compared to the EAP / T1O2 layers, by way of example. FIG. 7 shows the (A) Weibull distribution of electric breakdown; and the (B) polarization graph of the EAP / T1O2 layers and the EAP / T1O2: EAP / EAP layers at 75 V/pm. FIG. 7C provides the corresponding table of the electric breakdown strength EB, dissipation factor DF and polarization P, of the EAP / T1O2 and EAP / TiC^iEAP / EAP layers, obtained from the graphs of FIGS. 7A and 7B. From FIGS. 7A to 7C, it may be seen that the EAP / TiChiEAP / EAP layers exhibit a significantly larger electric breakdown strength EB of 103.8 MV/m, as compared to the EAP / T1O2 layers at varying concentrations of T1O2. For example, the electric breakdown strength EB of the EAP / TiC^iEAP / EAP layers may be 200 % of the EAP / T1O2 layers with a T1O2 weight ratio of 20 vol%. With reference to FIG. 7B, the polarization P of the EAP / TiC^iEAP / EAP layers may be similar to that of the EAP / T1O2 layers with a weight ratio of 20 vol%, and may exhibit a slimmer hysteresis loop suggesting lower dielectric loss. Further, the EAP / T1O2: EAP / EAP layers exhibit a lower dissipation factor DF as compared to the EAP / T1O2 layers with a T1O2 weight ratio of 20 vol%. In other words, the EAP / TiChiEAP / EAP layers exhibit increased electric breakdown strength EB and polarization P, with a lower dissipation factor DF and dielectric loss, when compared to the EAP / T1O2 layers with a T1O2 weight ratio of 20 vol% (indicated by arrows in FIG. 7C).

[0054] FIG. 8 shows a graph comparing the output force of the EAP / ZrC^EAP / EAP, the EAP / TiChiEAP / EAP layers, and neat EAP / EAP / EAP layers, by way of example. The neat EAP / EAP / EAP layers may include EAP layers (e.g. without the electroactive composite layer 130), for example, three layers of the EAP layers stacked on each other. It may be seen that the output force of the EAP / ZrC^: EAP / EAP and the EAP / T1O2: EAP / EAP layers may be higher than that of the neat EAP / EAP / EAP layers at increasing electric field strengths. For example, to produce an output force of 1 mN, the electric field strength required by the EAP/ ZrC^EAP / EAPand the EAP/ TiC^iEAP / EAP layers may be 10 MV/m, as compared to the neat EAP / EAP / EAP layers which requires a significantly higher electric field strength of 25 MV/m. As a further example, at a given electric field strength of 10 MV/m, the EAP / ZrC^EAP / EAP and the EAP / TiC^iEAP / EAP layers may produce a significantly higher output force, specifically, an output force which is 9.3 times, and 8.5 times, respectively, the output force produced by the neat EAP / EAP / EAP layers.

[0055] The layered electronic device 100 which may be produced by method 300 in accordance with to various embodiments, has following advantages:

- Increased dielectric strength, permittivity and polarizability, as compared to the neat EAP layers;

- Mitigation of the severe degradation of electric breakdown strength and dielectric loss;

- High resistance to electric breakdown in layered electronic devices due to the inclusion of the two EAP layers which sandwich the electroactive composite layer;

- Improved actuation performance at high allowed applied voltage / electric field without premature electric breakdown;

- High compatibility with standard layer coating processes, for example doctor blade, rod coating, bar coating, screen printing, slot die coating, spin coating, R2R coating and others;

- Patterning of areas with high and low dielectric permittivity is possible, through spatial control of the density of particles and hence, the control of the degree of dielectric permittivity within the layered electronic device;

- Flexibility in producing various haptic actuator designs (e.g. complex array or multi-stacked structures) and up-scaling;

[0056] The present disclosure also advantageously presents a facile, cost and time efficient production technique for layered electronic devices 100, in particular for flexible thin film piezoelectric, such as ferroelectric, polymer actuators for haptic feedback applications. The layered electronic device 100 in accordance with various embodiments, may provide higher actuation amplitudes while maintaining an allowed driving voltage. The layered electronic device 100 may also be employed in actuators with patterned or non-patterned electrodes and/or active layers as well as multi active layer designs.

[0057] Several examples of the disclosure refer to the layered electronic device including particles as ceramic particles. The present disclosure also envisages embodiments (e.g. of a layered electronic device) which includes metallic particles, for example, metallic particles. [0058] While the disclosure has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.