Artificial muscle actuator comprising electrodes with insulating double layer

Abstract

The present invention relates to an artificial muscle actuator including an electrode having an insulating double layer. The artificial muscle actuator includes a housing, a dielectric fluid housed within the housing, and an electrode pair positioned in the housing. The electrode pair includes a first electrode and a second electrode. The first electrode and the second electrode each include a metal film. The first electrode includes an insulating double layer disposed on the metal film of the first electrode in an orientation facing the second electrode. Further, the insulating double layer includes an acrylic and / or acrylate-based polymer layer disposed on the metal film and a biaxially oriented polypropylene (BOPP) layer disposed on the acrylic and / or acrylate-based polymer layer.

Description

Technical Field

[0001] This specification generally relates to artificial muscle actuators, and more specifically, to artificial muscle actuators comprising an insulating double layer. Background Technology

[0002] Electrostatically based artificial muscles, such as more specifically HASEL artificial muscles, are promising actuator technologies. A particular artificial muscle design is described in the paper entitled "Hydraulically amplified self-healing electrostatic actuators with muscle-like performance" by E. Acome, SK Mitchell, T. G Morrissey, M. M. Emmett, C. Benjamin, M. King, M. Radakowski, and C. Kepler (Science, January 5, 2018: Vol. 359, No. 6371, pp. 61-65). However, for practical applications, artificial muscle designs need to generate large forces at relatively low applied voltages.

[0003] Therefore, there is a need for improved artificial muscles capable of applying enhanced driving forces. Summary of the Invention

[0004] In one embodiment, the artificial muscle actuator includes: a housing, a dielectric fluid contained within the housing, and an electrode pair located within the housing. The electrode pair includes a first electrode and a second electrode. Each of the first and second electrodes includes a metal membrane. The first electrode includes an insulating bilayer disposed on the metal membrane of the first electrode with an orientation facing the second electrode. Additionally, the insulating bilayer includes an acrylic and / or acrylate-based polymer layer disposed on the metal membrane and a biaxially oriented polypropylene (BOPP) layer disposed on the acrylic and / or acrylate-based polymer layer.

[0005] In another embodiment, the artificial muscle actuator includes: a housing having an electrode region adjacent to an expandable fluid region, a dielectric fluid contained within the housing, and an electrode pair located in the electrode region of the housing. The electrode pair includes a first electrode and a second electrode. Each of the first and second electrodes includes a metal film and an insulating double layer disposed on the metal film. The insulating double layer of the first electrode is disposed on the metal film of the first electrode with an orientation facing the second electrode. The insulating double layer of the second electrode is disposed on the metal film of the second electrode with an orientation facing the first electrode. The insulating double layer includes an acrylic and / or acrylate-based polymer layer disposed on the metal film and a biaxially oriented polypropylene (BOPP) layer disposed on the acrylic and / or acrylate-based polymer layer. Furthermore, the electrode pair approaches in response to an applied voltage, pushing the dielectric fluid into the expandable fluid region, thereby hydraulically expanding the expandable fluid region.

[0006] In another embodiment, a method of driving an artificial muscle actuator includes: generating a voltage using a voltage source electrically connected to an electrode pair of the artificial muscle actuator, the artificial muscle actuator further comprising a housing having an electrode region and an expandable fluid region. A dielectric fluid is contained within the housing. The electrode pair is located in the electrode region of the housing. The electrode pair includes a first electrode and a second electrode, each having a metal film. The first electrode includes an insulating double layer disposed on the metal film of the first electrode with an orientation facing the second electrode. The insulating double layer includes an acrylic and / or acrylate-based polymer layer disposed on the metal film and a biaxially oriented polypropylene (BOPP) layer disposed on the acrylic and / or acrylate-based polymer layer. The method further includes: applying a voltage generated by the voltage source to the electrode pair, thereby electrostatically bringing the first and second electrodes together and pushing the dielectric fluid into the expandable fluid region, thereby hydraulically expanding the expandable fluid region. The method may further include: removing the voltage from the electrode pair, thereby removing the electrostatic attraction between the electrode pairs and causing the dielectric fluid to flow away from the expandable fluid region.

[0007] These and additional features provided by the embodiments described herein will be more fully understood in conjunction with the accompanying drawings and the following detailed description. Attached Figure Description

[0008] The embodiments illustrated in the accompanying drawings are illustrative and exemplary in nature and are not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments will be understood when considered in conjunction with the following drawings, in which the same reference numerals denote the same structures and wherein:

[0009] Figure 1A A schematic cross-sectional view of an example artificial muscle actuator in an undriven state according to one or more embodiments shown and described herein is illustrated.

[0010] Figure 1B This illustration schematically depicts one or more embodiments shown and described herein. Figure 1A A cross-sectional view of an artificial muscle actuator in the driven state;

[0011] Figure 2A A schematic cross-sectional view of another example of an artificial muscle actuator in an undriven state, according to one or more embodiments shown and described herein;

[0012] Figure 2B This illustration schematically depicts one or more embodiments shown and described herein. Figure 2A A cross-sectional view of an artificial muscle actuator in the driven state;

[0013] Figure 3 This illustration schematically shows one or more embodiments that can be implemented according to the examples shown and described herein. Figure 1A-2B A cross-sectional view of an example electrode pair used in an artificial muscle actuator.

[0014] Figure 4 This illustration schematically shows one or more embodiments that can be implemented according to the examples shown and described herein. Figure 1A-2B A cross-sectional view of another example of an electrode pair used in an artificial muscle actuator; and

[0015] Figure 5 The diagram illustrates the breakdown voltage / thickness of an example electrode insulating material according to one or more embodiments shown and described herein. Detailed Implementation

[0016] Referring generally to the accompanying drawings, embodiments of this disclosure relate to artificial muscle actuators having an electrode pair disposed within a housing containing a dielectric fluid. In operation, a voltage can be applied to the electrode pair, causing the electrode pair to come together, which directs the dielectric fluid into an expandable fluid region of the housing, causing the expandable fluid region of the housing to expand. This expansion can apply a driving force in many different applications, such as robotics, medical devices, vehicles, etc. Furthermore, at least one electrode of the electrode pair comprises an insulating double layer. Specifically, the insulating double layer of at least one electrode of the electrode pair comprises an acrylic and / or acrylate-based polymer layer (e.g., poly(ethyl acrylate acrylamide)) and a biaxially oriented polypropylene (BOPP) layer. The acrylic and / or acrylate-based polymer layer is disposed on a metal film of the electrode, and the BOPP layer is disposed on the acrylic and / or acrylate-based polymer layer. The insulating double layer of the electrode described herein has a high breakdown voltage / thickness, and thus facilitates the formation of a thin artificial muscle actuator resistant to high-voltage electrical breakdown and thereby capable of operating at high voltages, thereby facilitating increased achievable driving force. An embodiment of an artificial muscle actuator having electrodes with an insulating double layer will now be described, and the same reference numerals will be used throughout the figures to refer to the same or similar parts whenever possible.

[0017] Now for reference Figure 1A-2B This indicates the state when not driven ( Figure 1A and 2A ) and drive state ( Figure 1B and 2B Embodiments of artificial muscle actuators 100, 100' are described below. Artificial muscle actuators 100, 100' include a housing 110 and an electrode pair 150 disposed within the housing 110. The electrode pair 150 includes a first electrode 150a and a second electrode 150b. The electrode pair 150, including the first electrode 150a and the second electrode 150b, is disposed within an electrode region 116 of the housing 110 adjacent to an expandable fluid region 118 of the housing 110. Figure 1A and 1B In the embodiment of the artificial muscle actuator 100 shown, an electrode region 116 is disposed at a first end 111 of the housing 110, and an expandable fluid region 118 is disposed at a second end 113 of the housing 110. Figure 2A and 2B In the embodiment of the artificial muscle actuator 100' shown, the electrode region 116 is centrally disposed between an expandable fluid region 118 located at both the first end 111 and the second end 113 of the housing 110. It should be understood that the artificial muscle actuators 100, 100' provide non-limiting examples of artificial muscles that may include the electrode designs described herein. That is, the following regarding... Figure 3-5The electrodes 250a, 250b, 350a, 350b are described in more detail as including a metal film 252 and an insulating double layer 254 having an acrylic and / or acrylate polymer layer 256 and a biaxially oriented polypropylene (BOPP) layer 258.

[0018] In some embodiments, housing 110 comprises a flexible material and is a flexible housing. For example, the flexible housing may comprise an elastomeric material, making it an elastomeric housing. Housing 110 includes an outer surface 112 opposite to the inner surface 114 and is formed by one or more walls (which may be joined together or integral with each other). For example, housing 110 includes a first wall 115 opposite to the second wall 117 (in... Figure 1A-2B (described in the artificial muscle actuators 100 and 100') and a sidewall 119 extending between the first wall 115 and the second wall 117 at both the first end 111 and the second end 113 of the housing 110. Figure 1A and 1B (As described in the artificial muscle actuator 100).

[0019] Still referencing Figure 1A-2B One of the first electrode 150a and the second electrode 150b is a negatively charged electrode, and the other of the first electrode 150a and the second electrode 150b is a positively charged electrode. For the purposes of this discussion, either electrode 150a, 150b may be positively charged, provided that the other electrode 150a, 150b within the artificial muscle actuator 100, 100' is negatively charged. The electrode pair 150 of the artificial muscle actuator 100 is electrically connected to a voltage source 180, for example, using a wire 170. In operation, applying a voltage generated by the voltage source 180 to the electrode pair 150 creates a potential across the first electrode 150a and the second electrode 150b. This potential induces an electrostatic attraction between the first electrode 150a and the second electrode 150b, causing the first electrode 150a and the second electrode 150b to move closer together.

[0020] In addition to the electrode pair 150, the housing 110 contains a dielectric fluid 120. Without intending to be bound by theory, the dielectric fluid 120 is a medium or material that transmits electrical power in a minimal to non-conductive manner and therefore has low conductivity. Some non-limiting examples of the dielectric fluid 120 include perfluoroalkane, transformer oil, and deionized water. The dielectric fluid 120 minimizes unwanted discharges (i.e., short circuits) between the electrode pair 150. Furthermore, when the artificial muscle actuators 100, 100' are in an undriven state ( Figure 1A and 2AThe dielectric fluid 120 is disposed between the first electrode 150a and the second electrode 150b. When a voltage is applied to the electrode pair 150, the first electrode 150a and the second electrode 150b move closer together, thereby driving the artificial muscle actuators 100, 100' and pushing the dielectric fluid 120 into the expandable fluid region 118 of the housing 110.

[0021] exist Figure 1A In the undriven state of the artificial muscle actuator 100 shown, the electrode region 116 has a height substantially equal to that of the expandable fluid region 118. Figure 1B In the driven state of the artificial muscle actuator 100 shown, the expandable fluid region 118 has a greater height than the electrode region 116. In the undriven state ( Figure 1A The outer surfaces 112 of the housing 110, along both the first wall 115 and the second wall 117, are flat and substantially parallel to each other. More specifically, the first distance D1 along the outer surfaces 112 of the housing 110 between the first wall 115 and the second wall 117 within the electrode region 116 is substantially equal to the second distance D2 along the outer surfaces 112 of the housing 110 between the first wall 115 and the second wall 117 within the expandable fluid region 118. In the driven state ( Figure 1B The first electrode 150a and the second electrode 150b are in contact with each other.

[0022] Therefore, the first electrode 150a and the second electrode 150b are now substantially parallel to each other. However, in the driven state, the outer surface 112 of the first wall 115 of the housing 110 within the electrode region 116 is not parallel to the outer surface 112 of the second wall 117 of the housing 110. More specifically, the first distance D1 between the outer surfaces 112 of the first wall 115 and the second wall 117 within the electrode region 116 is less than the third distance D3 between the outer surfaces 112 of the first wall 115 and the second wall 117 within the expandable fluid region 118. The difference between the second distance D2 and the third distance D3 defines the expansion amount of the first wall 115 of the housing 110 within the expandable fluid region 118 by the displaced dielectric fluid 120.

[0023] In some implementation schemes, such as Figure 1A and 1BAs shown, the first electrode 150a and the second electrode 150b are arranged such that the distance between the first electrode 150a and the second electrode 150b is closer to the first end 111 of the housing 110 than to the second end 113 of the housing. This positions the first electrode 150a and the second electrode 150b in an acute angle or V-shape configuration. As a result, when actuated, the electrodes 150a and 150b are configured to be close to each other in a zipper-like manner, pushing the dielectric fluid 120 toward the second end 113 of the housing 110 and into the expandable fluid region 118. This pushes the dielectric fluid 120 from the first end 111 of the housing 110 toward the second end 113 and into the expandable fluid region 118. In the expandable fluid region 118, the pressure from the dielectric fluid 120 against the first wall 115 (and / or the second wall 117) of the housing 110 causes the first wall 115 (and / or the second wall 117) to deform (i.e. expand). Once the voltage applied to the first electrode 150a and the second electrode 150b is discontinuous, electrodes 150a and 150b return to their initial positions. Figure 1A (in the non-parallel position) and return to its initial position along the outer surface 112 of both the first wall 115 and the second wall 117. Figure 1A (parallel position in the text). In some implementations, such as Figure 1A and 1B As shown, a reinforcing membrane 140 is provided between the first electrode 150a and the first wall 115 of the housing 110. When operating between a non-driven state and a driven state and as the first electrode 150a moves toward the second electrode 150b and the second wall 117, the reinforcing membrane 140 provides rigidity to at least a portion of the first wall 115. In some embodiments, the reinforcing membrane 140 may be a cellulose acetate film.

[0024] Now for reference Figure 2A and 2B The artificial muscle actuator 100' is driven similarly to Figure 1A and 1B The artificial muscle actuator 100 is driven. However, in Figure 2A and 2B In the middle, electrodes 150a and 150b are in the undriven state ( Figure 2A ) and drive state ( Figure 2B They are basically parallel below. Figure 2A and 2B Electrostatically bringing electrodes 150a and 150b together guides dielectric fluid from electrode region 116 outward into one or more expandable fluid regions 118, causing the expandable fluid regions 118 to expand. It should be understood that this includes... Figure 2A and 2B To illustrate another design for an artificial muscle actuator that may include the electrode design described herein. That is, the following regarding... Figure 3-5The electrodes 250a, 250b, 350a, 350b are described in more detail as including a metal film 252 and an insulating double layer 254 having an acrylic and / or acrylate polymer layer 256 and a biaxially oriented polypropylene (BOPP) layer 258.

[0025] Now for reference Figure 3 and 4 Schematic illustration of what can be done Figure 1A-2B Two implementation schemes of electrode pairs used in artificial muscle actuators 100, 100'. Figure 3 The first electrode 250a and the second electrode 250b are shown, and Figure 4 The first electrode 350a and the second electrode 350b are shown. Figure 3 Electrodes 250a, 250b and Figure 4 Electrodes 350a and 350b both include a metal film 252 and an insulating double layer 254 disposed on the metal film 252. Furthermore, the structure... Figure 3 Electrodes 250a, 250b and Figure 4 The electrodes 350a and 350b are arranged such that the insulating double layer 254 of the first electrodes 250a and 350a is disposed on the metal film 252 of the first electrodes 250a and 350a with an orientation facing the second electrodes 250b and 350b. As an example, in... Figure 3 In this configuration, the insulating double layer 254 of the first electrode 250a surrounds the metal film 252 of the first electrode 250a, and a portion of the insulating double layer 254 of the first electrode 250a faces the second electrode 250b. Figure 3 In this configuration, the second electrode 250b also includes an insulating double layer 254 of the metal film 252 of the second electrode 250b, and a portion of the insulating double layer 254 of the second electrode 250b faces the first electrode 250a. As another example, in... Figure 4 In this process, the insulating double layer 254 of the first electrode 350a is disposed on the surface of the metal film 252 of the first electrode 350a facing the second electrode 350b, but does not surround the metal film 252. Figure 4 In the first electrode 350a, the second electrode 250b also includes an insulating double layer 254 disposed on the surface of the metal film 252 of the second electrode 250b facing the first electrode 350a, but not surrounding the metal film 252.

[0026] Furthermore, despite Figure 3 Electrodes 250a, 250b and Figure 4Electrodes 350a and 350b each include a metal film 252 and an insulating double layer 254 disposed on the metal film 252. It should be understood that embodiments in which the insulating double layer 254 is disposed on only one of the two electrodes 250a, 250b and 350a, 350b of each electrode pair are included. Indeed, a single insulating double layer 254, if oriented with one electrode (e.g., 250a, 350a) facing the other electrode (e.g., 250b, 350b), provides insulating separation between the electrode pairs (250a, 250b, 350a, 350b).

[0027] Still referencing Figure 3 and 4 The insulating double layer 254 comprises an acrylic and / or acrylate polymer layer 256 disposed on the metal film 252 and a biaxially oriented polypropylene (BOPP) layer 258 disposed on the acrylic and / or acrylate polymer layer 256. The acrylic and / or acrylate polymer layer 256 is an adhesive layer (e.g., an acrylic adhesive emulsion) adhered to the metal film 252 and the BOPP layer 258. In some embodiments, the acrylic and / or acrylate polymer layer 256 comprises poly(ethyl acrylate acrylamide). However, it should be understood that this includes acrylic and / or acrylate polymer materials such as mono(ethyl acrylate acrylamide), poly(methyl acrylate acrylamide), poly(propyl acrylate acrylamide), poly(butyl acrylate acrylamide), poly(pentyl acrylate acrylamide), poly(hexyl acrylate acrylamide), etc. Furthermore, the metal film 252 (which may be a flexible metal film) may comprise aluminum or copper. However, it should be understood that any suitable metal used to form the electrode may be included. Additionally, it should be understood that an additional intermediate layer may be located between the insulating double layer 254 and the metal layer 252, and that the additional intermediate layer may be located between the insulating double layer 254 and the housing 110.

[0028] Still referencing Figure 3 and 4 The insulating layer 254 may have a thickness T of less than 50 μm, for example, less than 45 μm, less than 40 μm, less than 35 μm, less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm, less than 10 μm, or less than 5 μm. BL Or any range having any two of these thicknesses as endpoints. For example... Figure 3 and 4 As shown, the acrylic and / or acrylate polymer layer 256 comprises a thickness T IL And BOPP layer 258 including thickness T OLIn some embodiments, the thickness T of the acrylic and / or acrylate-based polymer layer 256 is... IL Thickness T greater than 258 BOPP layer OL For example, 1.5-10 times thick, or 2-5 times thick.

[0029] Now for reference Figure 5 Figure 20 graphically illustrates the breakdown voltage / thickness (kV / μm) of the example electrode insulation material (e.g., the example insulating double layer) to demonstrate the effectiveness of the insulating double layer 254, comprising an acrylic and / or acrylate polymer layer 256 and a BOPP layer 258, compared to other insulation materials. Figure 20 includes 11 columns (columns 22-40) describing the breakdown voltage / thickness of 10 comparative electrode insulation materials (columns 22-38) and the insulating double layer 254 (column 40) comprising an acrylic and / or acrylate polymer layer 256 and a BOPP layer 258.

[0030] Column 22 display A 25.4 μm thick insulating double layer (e.g., polyimide) with an acrylic adhesive has a breakdown voltage of 0.22 kV / μm / thickness. Column 24 shows... The 25.4 μm thick insulating double layer with silicone adhesive has a breakdown voltage of 0.22 kV / μm / thickness. (Column 26 shows...) The 50.8 μm thick insulating double layer with silicone adhesive has a breakdown voltage of 0.18 kV / μm / thickness. (Column 28 shows...) A 76.2 μm thick insulating double layer (e.g., polyetherimide) with an acrylic adhesive has a breakdown voltage / thickness of 0.16 kV / μm. Column 30 shows... The 127μm thick insulating double layer with acrylic adhesive has a breakdown voltage / thickness of 0.1kV / μm. Column 32 shows High Density. A 50.8 μm thick insulating double layer (e.g., polytetrafluoroethylene (PTFE)) bonded to silicone resin has a breakdown voltage of 0.2 kV / μm / thickness. Column 34 shows... The 50.8 μm thick insulating double layer with silicone adhesive has a breakdown voltage of 0.18 kV / μm / thickness. Column 36 shows the tensile strength. The 63.5 μm thick insulating double layer with silicone adhesive has a breakdown voltage / thickness of 0.19 kV / μm. (Column 38 shows...) The 76.2 μm thick insulating double layer with silicone adhesive has a breakdown voltage of 0.12 kV / μm / thickness.

[0031] Therefore, each of the insulating double layers represented by columns 22-38 has a breakdown voltage / thickness of 0.1-0.22 kV / μm. In contrast, column 40 shows that the 19 μm thick insulating double layer 254, comprising an acrylic and / or acrylate polymer layer 256 (with a thickness of 13.4 μm) and a BOPP layer 258 (with a thickness of 3.95 μm), has a breakdown voltage / thickness of 1.04 kV / μm. This indicates an improvement of more than four times compared to the best comparable insulating double layer represented by columns 22-38. It also shows that the breakdown voltage / thickness of insulating double layer 254 is above 1 kV / μm.

[0032] By using an insulating double layer 254 comprising an acrylic and / or acrylate polymer layer 256 and a BOPP layer 258, the thickness T of the insulating double layer 254 can be reduced. BL This also increases the electrical breakdown voltage of the insulating double layer 254, allowing the artificial muscle actuators 100 and 100' to operate at higher voltages without short circuits, thus promoting the formation of more powerful artificial muscle actuators. For example, the insulating double layer 254 withstands breakdown voltages above 10 kV, such as above 11 kV, 12 kV, 15 kV, 20 kV, etc. Indeed, the increased breakdown voltage / thickness of the insulating double layer 254 allows a single insulating double layer 254 to provide sufficient insulation separation between the electrode pairs (250a, 250b and 350a, 350b). Without intending to be bound by theory, in operation, the driving force applied by the artificial muscle actuators 100 and 100' is related to the thickness T of the insulating double layer 254. BL It is inversely proportional to and directly proportional to the square of the applied voltage. Therefore, reducing the thickness of the insulating double layer 254 while using materials that withstand electrical short circuits under large applied voltages, such as acrylic and / or acrylate-based polymer layers 256 and BOPP layers 258, promotes an increase in the achievable driving force.

[0033] It should now be understood that the embodiments described herein relate to artificial muscle actuators having electrode pairs, wherein at least one electrode comprises an insulating bilayer comprising an acrylic and / or acrylate-based polymer layer (e.g., poly(ethyl acrylate acrylamide)) and a BOPP layer. The insulating bilayer has a high breakdown voltage / thickness and thus facilitates the formation of thin artificial muscle actuators resistant to high-voltage electrical breakdown, enabling them to operate at higher voltages, thereby facilitating increased achievable actuation force.

[0034] To clarify, the terms “substantially” and “about” may be used herein to indicate the inherent degree of uncertainty, which may be attributed to any quantitative comparison, value, measurement result, or other representation. These terms are also used herein to indicate the extent to which a quantitative representation may vary from a specified reference value without causing a change in the essential function of the subject matter under discussion.

[0035] While specific embodiments have been described and illustrated herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Furthermore, although various aspects of the claimed subject matter have been described herein, these aspects need not be used in combination. Therefore, the appended claims are intended to cover all such changes and modifications within the scope of the claimed subject matter.

Claims

1. An artificial muscle actuator comprising: a housing; a dielectric fluid contained within the housing; and a pair of electrodes positioned in the housing, wherein: the pair of electrodes comprises a first electrode and a second electrode; the first electrode and the second electrode each comprise a metal film; the first electrode comprises an insulating bilayer disposed on the metal film of the first electrode in an orientation facing the second electrode; and the insulating bilayer comprises an acrylic and / or acrylate-based polymer layer disposed on the metal film and a biaxially oriented polypropylene (BOPP) layer disposed on the acrylic and / or acrylate-based polymer layer, wherein the acrylic and / or acrylate-based polymer layer comprises poly(ethyl acrylate) acrylamide.

2. The artificial muscle actuator of claim 1, wherein the acrylic and / or acrylate-based polymer layer is an adhesive layer adhered to the metal film and the BOPP layer.

3. The artificial muscle actuator of claim 1, wherein the second electrode comprises an insulating bilayer disposed on the metal film of the second electrode in an orientation facing the first electrode.

4. The artificial muscle actuator of claim 1, wherein the insulating bilayer surrounds the metal film of the first electrode.

5. The artificial muscle actuator of claim 4, wherein the second electrode comprises an insulating bilayer that surrounds the metal film of the second electrode.

6. The artificial muscle actuator of claim 1, wherein the insulating bilayer comprises a thickness of 25 microns or less.

7. The artificial muscle actuator of claim 1, wherein the insulating bilayer is resistant to a breakdown voltage of 11 kV or more.

8. The artificial muscle actuator of claim 1, wherein the breakdown voltage / thickness of the insulating bilayer is 1 kV / pm or more.

9. The artificial muscle actuator of claim 1, wherein the metal film of the first electrode and the second electrode comprises a flexible metal film.

10. An artificial muscle actuator comprising: a housing comprising an electrode region adjacent to an expandable fluid region; a dielectric fluid contained within the housing; and a pair of electrodes positioned in the electrode region of the housing, wherein: the pair of electrodes comprises a first electrode and a second electrode; the first electrode and the second electrode each comprise a metal film and an insulating bilayer disposed on the metal film; the insulating bilayer of the first electrode is disposed on the metal film of the first electrode in an orientation facing the second electrode; the insulating bilayer of the second electrode is disposed on the metal film of the second electrode in an orientation facing the first electrode; the insulating bilayer comprises an acrylic and / or acrylate-based polymer layer disposed on the metal film and a biaxially oriented polypropylene (BOPP) layer disposed on the acrylic and / or acrylate-based polymer layer, wherein the acrylic and / or acrylate-based polymer layer comprises poly(ethyl acrylate) acrylamide; and the pair of electrodes converge in response to an applied voltage, pushing the dielectric fluid into the expandable fluid region to hydraulically expand the expandable fluid region.

11. The artificial muscle actuator of claim 10, wherein the housing is a flexible housing comprising an elastomeric material.

12. The artificial muscle actuator of claim 10, further comprising a reinforcing film between one of the first electrode or the second electrode and the housing. ​ ​ 13. The artificial muscle actuator of claim 10, wherein the breakdown voltage / thickness of the insulating bilayer is 1 kV / μιη or more.

14. A method of actuating an artificial muscle actuator, the method comprising: generating a voltage using a voltage source electrically connected to a pair of electrodes of the artificial muscle actuator, the artificial muscle actuator further comprising a housing having an electrode region and an expandable fluid region; wherein: a dielectric fluid is contained within the housing; the pair of electrodes is located in the electrode region of the housing; the pair of electrodes comprises a first electrode and a second electrode, the first electrode and the second electrode each comprising a metal film; the first electrode includes an insulating bilayer disposed on the metal film of the first electrode in an orientation facing the second electrode; and the insulating bilayer includes an acrylic and / or acrylate-based polymer layer disposed on the metal film and a biaxially oriented polypropylene (BOPP) layer disposed on the acrylic and / or acrylate-based polymer layer, wherein the acrylic and / or acrylate-based polymer layer includes poly(ethyl acrylate) acrylamide; and applying the voltage generated by the voltage source to the pair of electrodes, thereby electrostatically drawing the first electrode and the second electrode together, pushing the dielectric fluid into the expandable fluid region to thereby hydraulically expand the expandable fluid region.

15. The method of claim 14, further comprising: removing the voltage from the pair of electrodes, thereby removing the electrostatic attraction between the pair of electrodes such that the dielectric fluid flows away from the expandable fluid region.

16. The method of claim 14, wherein the voltage applied to the pair of electrodes is 11 kV or more.

17. The method of claim 14, wherein the breakdown voltage / thickness of the insulating bilayer is 1 kV / μιη or more.

18. The method of claim 14, wherein the second electrode includes an insulating bilayer disposed on the metal film of the second electrode in an orientation facing the first electrode.

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