Artificial muscle stack with alternating offset artificial muscle layers

Abstract

To provide an artificial muscle stack that comprises a plurality of artificial muscle layers.SOLUTION: Each artificial muscle layer includes one or more artificial muscles having a housing with an electrode region and an expandable fluid region, a dielectric fluid housed in the housing, and an electrode pair having first and second electrodes positioned in the electrode region. The first and second electrodes each include two or more tab portions and two or more bridge portions. The two or more bridge portions interconnect adjacent tab portions. At least one of the first and second electrodes includes a central opening positioned between the tab portions and encircling the expandable fluid region. The artificial muscle layers are arranged such that the expandable fluid region of the artificial muscles of each artificial muscle layer overlaps at least one tab portion of one or more artificial muscles of an adjacent artificial muscle layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This specification relates generally to artificial muscle stacks and arrangements. [Background technology]

[0002] Current robotics technology relies on rigid components, such as servo motors, to perform tasks, often in structured environments. This rigidity creates limitations in many robotic applications, caused at least in part by the weight-to-power ratio of servo motors and other rigid robotic devices. The field of soft robotics ameliorates these limitations by using artificial muscles and soft actuators. Artificial muscles attempt to mimic the versatility, performance, and reliability of biological muscles. Some artificial muscles rely on fluidic actuators, which require a supply of pressurized gas or liquid, and fluid transport must occur through a system of channels and tubing, limiting the speed and efficiency of artificial muscles. Other artificial muscles use heat-activated polymer fibers, which are difficult to control and operate with low efficiency.

[0003] One particular artificial muscle design is described in a paper titled "Hydraulically amplified self-healing electrostatic actuators with muscle-like performance" by E. Acome, S.K. Mitchell, T.G. Morrissey, M.B. Emmett, C. Benjamin, M. King, M. Radakovitz, and C. Keplinger (Science 05 Jan 2018: Vol. 359, Issue 6371, pp. 61-65). These hydraulically amplified self-healing electrostatic (HASEL) actuators use electrostatic and hydraulic forces to achieve various actuation modes. However, HASEL actuator artificial muscles have limited actuator power per unit volume. Furthermore, HASEL actuator artificial muscles and other known artificial muscles are difficult to combine in a small footprint while simultaneously increasing the achievable collective force of these artificial muscle combinations.

[0004] Therefore, there is a need for improved artificial muscles with increased actuator power per unit volume, and small footprint arrangements of these improved artificial muscles. Summary of the Invention

[0005] In one embodiment, an artificial muscle stack includes multiple artificial muscle layers. Each artificial muscle layer includes one or more artificial muscles, each of which includes a housing having an electrode region and an expandable fluid region, a dielectric fluid contained within the housing, and an electrode pair having first and second electrodes positioned in the electrode region. The first and second electrodes each include two or more tab portions and two or more bridge portions. Each of the two or more bridge portions interconnects adjacent tab portions. At least one of the first and second electrodes includes a central opening positioned between the two or more tab portions and circumventing the expandable fluid region. Additionally, the multiple artificial muscle layers are arranged such that the expandable fluid region of one or more artificial muscles in each artificial muscle layer overlaps at least one tab portion of one or more artificial muscles in an adjacent artificial muscle layer.

[0006] In another embodiment, the artificial muscle stack includes three or more artificial muscle layers. Each artificial muscle layer includes one or more artificial muscles. The one or more artificial muscles include a housing having an electrode region and an expandable fluid region, a dielectric fluid contained within the housing, and an electrode pair having first and second electrodes positioned in the electrode region. The first and second electrodes each include two or more tab portions and two or more bridge portions. Each of the two or more bridge portions interconnects adjacent tab portions. At least one of the first and second electrodes includes a central opening positioned between the two or more tab portions and circumventing the expandable fluid region. Furthermore, each inner artificial muscle layer is offset from a first adjacent artificial muscle layer along a first tab axis and from a second adjacent artificial muscle layer along a second tab axis, with each tab axis extending from a central axis of the expandable fluid region to an end of at least one of the tab portions of one or more artificial muscles of the inner artificial muscle layer.

[0007] In yet another embodiment, a method for actuating an artificial muscle stack includes generating a voltage using a power source electrically coupled to an electrode pair of each artificial muscle of a plurality of artificial muscle layers. Each artificial muscle includes a housing having an electrode region and an expandable fluid region, a dielectric fluid is contained within the housing, and the electrode pair includes a first electrode and a second electrode and is positioned in the electrode region of the housing. The first electrode and the second electrode each include two or more tab portions and two or more bridge portions, each of the two or more bridge portions interconnecting adjacent tab portions, and at least one of the first electrode and the second electrode is positioned between the two or more tab portions and includes a central opening circumventing the expandable fluid region. The plurality of artificial muscle layers are arranged such that the expandable fluid region of each artificial muscle of each artificial muscle of each artificial muscle layer overlaps the tab portion of at least one artificial muscle of one or more artificial muscles of an adjacent artificial muscle layer. The method further includes applying a voltage to an electrode pair of at least one artificial muscle of at least one of the plurality of artificial muscle layers, thereby actuating the electrode pair of the at least one artificial muscle from an unactuated state to an actuated state, such that a dielectric fluid is directed into the expandable fluid region of the housing and expands the expandable fluid region.

[0008] These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description taken in conjunction with the drawings. [Brief explanation of the drawings]

[0009] The embodiments set forth in the 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 illustrative embodiments can be understood when read in conjunction with the following drawings, in which like structure is indicated with like reference numerals and in which:

[0010] [Figure 1] FIG. 1 is an exploded view that schematically depicts an exemplary artificial muscle, according to one or more embodiments shown and described herein. [Figure 2]FIG. 2 is a top view that schematically depicts the artificial muscle of FIG. 1 according to one or more embodiments shown and described herein. [Figure 3A] FIG. 3 is a cross-sectional view that schematically depicts the artificial muscle of FIGS. 1 and 2 taken along line 3-3 of FIG. 2 in an unactuated state, according to one or more embodiments shown and described herein. [Figure 3B] FIG. 3 is a cross-sectional view that schematically depicts the artificial muscle of FIG. 1 taken along line 3-3 of FIG. 2 in an actuated state, according to one or more embodiments shown and described herein. [Figure 4A] FIG. 1 is a cross-sectional view that schematically depicts another exemplary artificial muscle in an unactuated state, in accordance with one or more embodiments shown and described herein. [Figure 4B] FIG. 4B is a cross-sectional view that schematically depicts the artificial muscle of FIG. 4A in an actuated state, according to one or more embodiments shown and described herein. [Figure 5A] FIG. 1 is a top view that schematically depicts an example artificial muscle stack comprising multiple artificial muscle layers positioned in coaxial alignment, according to one or more embodiments shown and described herein. [Figure 5B] FIG. 5B is a side view that schematically depicts the artificial muscle stack of FIG. 5A along line 5B-5B in an unactuated state, according to one or more embodiments shown and described herein. [Figure 5C] FIG. 5B is a side view that schematically depicts the artificial muscle stack of FIG. 5A along line 5B-5B in an actuated state, according to one or more embodiments shown and described herein. [Figure 6A] FIG. 1 is a top view that schematically depicts an example artificial muscle stack comprising multiple artificial muscle layers positioned in an alternating offset arrangement, according to one or more embodiments shown and described herein. [Figure 6B] FIG. 6B is a side view that schematically depicts the artificial muscle stack of FIG. 6A along line 6B-6B in an unactuated state, according to one or more embodiments shown and described herein. [Figure 6C]FIG. 6B is a side view that schematically depicts the artificial muscle stack of FIG. 6A along line 6B-6B in an actuated state, according to one or more embodiments shown and described herein. [Figure 6D] FIG. 6D is a side view that schematically depicts the artificial muscle stack of FIG. 6A along line 6D-6D in an unactuated state, according to one or more embodiments shown and described herein. [Figure 6E] FIG. 6D is a side view that schematically depicts the artificial muscle stack of FIG. 6A along line 6D-6D in an unactuated state, according to one or more embodiments shown and described herein. [Figure 7] FIG. 1 is a top view that schematically depicts an example artificial muscle stack comprising multiple artificial muscle layers positioned in an alternating offset arrangement with the addition of peripheral artificial muscles, according to one or more embodiments shown and described herein. [Figure 8] FIG. 8A is a schematic depiction of an actuation system for operating the artificial muscles of the artificial muscle stack of FIGS. 5A-7, according to one or more embodiments shown and described herein. DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiments described herein are directed to an artificial muscle stack including multiple artificial muscle layers, each having at least one artificial muscle arranged to maximize packing of the individual artificial muscles. Each individual artificial muscle described herein is actuable to selectively raise and lower a region of the artificial muscle to provide a selective, on-demand, expanded, expandable fluid region. In particular, one or more artificial muscles each include an electrode pair that can be drawn together by application of a voltage, thereby forcing a dielectric fluid into the expandable fluid region, expanding the expandable fluid region, and raising a portion of the artificial muscle on demand. The first electrode and the second electrode each include two or more tab portions and two or more bridge portions interconnecting adjacent tab portions, and at least one of the first electrode and the second electrode includes a central opening positioned between the tab portions and circumnavigating the expandable fluid region. The design of the tab portions and bridge portions of the electrode pair promotes a zippering actuation motion to increase the force per unit volume achievable by actuation of the artificial muscle.

[0012] In some applications, individual artificial muscles do not generate enough actuation force to perform some desired functionality. In these applications, it may be useful to arrange a stack of artificial muscles arranged in a layer array to increase the available actuation force. However, increasing the number of artificial muscles in each layer increases the footprint of the artificial muscle stack. In some applications, it may be useful to minimize the footprint of the artificial muscle stack while retaining the benefits of increased actuation force. Embodiments described herein are directed to artificial muscle stacks comprising multiple artificial muscle layers stacked in an alternating offset arrangement such that the expandable fluid region of each of the one or more artificial muscles in each artificial muscle layer overlaps at least one tab portion of the one or more artificial muscles in an adjacent artificial muscle layer. This alternating offset arrangement increases the number of artificial muscles that can be arranged in a particular footprint, facilitating an increase in the achievable actuation force of the artificial muscle stack while maintaining a small footprint. Various embodiments of artificial muscle stacks are described in further detail herein. Whenever possible, the same reference numbers are used throughout the drawings to refer to the same or similar parts.

[0013] 1 and 2, an example artificial muscle 100 is schematically depicted that can be disposed in the artificial muscle stack 201, 301, 301′ (FIGS. 5A-7). The artificial muscle 100 comprises a housing 110, an electrode pair 104 including a first electrode 106 and a second electrode 108 secured to opposing sides of the housing 110, a first electrical insulator layer 111 secured to the first electrode 106, and a second electrical insulator layer 112 secured to the second electrode 108. In some embodiments, the housing 110 is a one-piece monolithic layer that includes a pair of opposing inner surfaces, such as a first inner surface 114 and a second inner surface 116, and a pair of opposing outer surfaces, such as a first outer surface 118 and a second outer surface 120. In some embodiments, the first inner surface 114 and the second inner surface 116 of the housing 110 are heat-sealable. In other embodiments, the housing 110 may be a pair of individually fabricated film layers, such as a first film layer 122 and a second film layer 124. Thus, the first film layer 122 includes a first inner surface 114 and a first outer surface 118, and the second film layer 124 includes a second inner surface 116 and a second outer surface 120.

[0014] It should be understood that although the embodiments described herein primarily refer to the housing 110 as comprising a first film layer 122 and a second film layer 124, as opposed to a one-piece housing, either arrangement is contemplated. In some embodiments, the first film layer 122 and the second film layer 124 generally comprise the same structure and composition. For example, in some embodiments, the first film layer 122 and the second film layer 124 each comprise biaxially oriented polypropylene.

[0015] The first electrode 106 and the second electrode 108 are each positioned between the first film layer 122 and the second film layer 124. In some embodiments, the first electrode 106 and the second electrode 108 are each an aluminum-coated polyester, such as Mylar®. In addition, one of the first electrode 106 and the second electrode 108 is a negatively charged electrode, and the other of the first electrode 106 and the second electrode 108 is a positively charged electrode. For purposes discussed herein, either electrode 106, 108 can be positively charged as long as the other electrode 106, 108 of the artificial muscle 100 is negatively charged.

[0016] The first electrode 106 has a film-facing surface 126 and an opposite inner surface 128. The first electrode 106 is positioned against the first film layer 122, specifically against the first inner surface 114 of the first film layer 122. Additionally, the first electrode 106 includes a first terminal 130 that extends from the first electrode 106 past an edge of the first film layer 122 such that the first terminal 130 can be connected to a power source to activate the first electrode 106. Specifically, the terminal is coupled, directly or in series, to a power source and controller of the actuation system 400, as shown in FIG. 7 . Similarly, the second electrode 108 has a film-facing surface 148 and an opposite inner surface 150. The second electrode 108 is positioned against the second film layer 124, specifically against the second inner surface 116 of the second film layer 124. The second electrode 108 includes a second terminal 152 that extends from the second electrode 108 past the edge of the second film layer 124 such that the second terminal 130 can be connected to a power source and controller of the actuation system 400 to actuate the second electrode 108.

[0017] The first electrode 106 includes two or more tab portions 132 and two or more bridge portions 140. Each bridge portion 140 is positioned between and interconnects adjacent tab portions 132. Each tab portion 132 has a first end 134 extending radially from the central axis C of the first electrode 106 to an opposing second end 136 of the tab portion 132, which defines a portion of the outer periphery 138 of the first electrode 106. Each bridge portion 140 has a first end 142 extending from the central axis C of the first electrode 106 to an opposing second end 144 of the bridge portion 140, which defines another portion of the outer periphery 138 of the first electrode 106. Each tab portion 132 has a tab length L1, and each bridge portion 140 has a bridge length L2 extending radially from the central axis C of the first electrode 106. Tab length L1 is the distance from first end 134 to second end 136 of tab portion 132, and bridge length L2 is the distance from first end 142 to second end 144 of bridge portion 140. Tab length L1 of each tab portion 132 is longer than bridge length L2 of each bridge portion 140. In some embodiments, bridge length L2 is 20% to 50% of tab length L1, such as 30% to 40% of tab length L1.

[0018] In some embodiments, the two or more tab portions 132 are arranged in one or more pairs of tab portions 132. Each pair of tab portions 132 includes two tab portions 132 positioned radially opposite one another. In some embodiments, the first electrode 106 may include only two tab portions 132 positioned on opposite sides or opposite ends of the first electrode 106. In some embodiments, as shown in FIGS. 1 and 2 , the first electrode 106 includes four tab portions 132 and four bridge portions 140 interconnecting adjacent tab portions 132. In this embodiment, the four tab portions 132 are arranged such that two pairs of tab portions 132 are radially opposed to one another. Additionally, as shown, the first terminal 130 extends from and is integrally formed with the second end 136 of one of the tab portions 132.

[0019] Like the first electrode 106, the second electrode 108 includes at least a pair of tab portions 154 and two or more bridge portions 162. Each bridge portion 162 is positioned between and interconnects adjacent tab portions 154. Each tab portion 154 has a first end 156 that extends radially from a central axis C of the second electrode 108 to an opposing second end 158 of the tab portion 154, which defines a portion of an outer periphery 160 of the second electrode 108. Due to the first electrode 106 and the second electrode 108 being coaxial with each other, the central axes C of the first electrode 106 and the second electrode 108 are the same. Each bridge portion 162 has a first end 164 extending radially from the central axis C of the second electrode 108 to an opposing second end 166 of the bridge portion 162 that defines another portion of the outer periphery 160 of the second electrode 108. Each tab portion 154 has a tab length L3, and each bridge portion 162 has a bridge length L4 that extends radially from the central axis C of the second electrode 108. The tab length L3 is the distance from the first end 156 to the second end 158 of the tab portion 154, and the bridge length L4 is the distance from the first end 164 to the second end 166 of the bridge portion 162. The tab length L3 is longer than the bridge length L4 of each bridge portion 162. In some embodiments, the bridge length L4 is between 20% and 50% of the tab length L3, such as between 30% and 40% of the tab length L3.

[0020] In some embodiments, the two or more tab portions 154 are arranged in one or more pairs of tab portions 154. Each pair of tab portions 154 includes two tab portions 154 positioned radially opposite one another. In some embodiments, the second electrode 108 may include only two tab portions 154 positioned on opposite sides or opposite ends of the first electrode 106. In some embodiments, as shown in FIGS. 1 and 2, the second electrode 108 includes four tab portions 154 and four bridge portions 162 interconnecting adjacent tab portions 154. In this embodiment, the four tab portions 154 are arranged such that two pairs of tab portions 154 are radially opposed to one another. Additionally, as shown, the second terminal 152 extends from and is integrally formed with the second end 158 of one of the tab portions 154.

[0021] 1-4B, at least one of the first electrode 106 and the second electrode 108 has a central opening formed between the first end 134 of the tab portion 132 and the first end 142 of the bridge portion 140. In FIGS. 3A and 3B, the first electrode 106 has a central opening 146. However, it should be understood that the first electrode 106 need not include the central opening 146 when a central opening is provided in the second electrode 108, as shown in FIGS. 4A and 4B. Alternatively, the second electrode 108 need not include a central opening when a central opening 146 is provided in the first electrode 106. Still referring to FIGS. 1-4B, the first electrical insulator layer 111 and the second electrical insulator layer 112 have geometric shapes generally corresponding to the first electrode 106 and the second electrode 108, respectively. Thus, the first and second electrical insulator layers 111, 112 each have tab portions 170, 172 and bridge portions 174, 176 that correspond to similar portions of the first and second electrodes 106, 108. Furthermore, the first and second electrical insulator layers 111, 112 each have outer perimeters 178, 180 that, when positioned over the first and second electrodes 106, 108, correspond to the outer perimeter 138 of the first electrode 106 and the outer perimeter 160 of the second electrode 108, respectively.

[0022] It should be understood that in some embodiments, first electrical insulator layer 111 and second electrical insulator layer 112 generally comprise the same structure and composition. As such, in some embodiments, first electrical insulator layer 111 and second electrical insulator layer 112 each comprise adhesive surfaces 182, 184 and opposing non-sealable surfaces 186, 188, respectively. In some embodiments, first electrical insulator layer 111 and second electrical insulator layer 112 are each polymeric tapes adhered to inner surface 128 of first electrode 106 and inner surface 150 of second electrode 108, respectively.

[0023] 2-4B, artificial muscle 100 is shown in an assembled configuration with first terminal 130 of first electrode 106 and second terminal 152 of second electrode 108, i.e., first film layer 122 and second film layer 124, extending past the outer periphery of housing 110. As shown in FIG. 2, second electrode 108 is laminated on top of first electrode 106; therefore, first electrode 106, first film layer 122, and second film layer 124 are not shown. In the assembled configuration, first electrode 106, second electrode 108, first electrical insulator layer 111, and second electrical insulator layer 112 are sandwiched between first film layer 122 and second film layer 124. The first film layer 122 is partially sealed to the second film layer 124 in an area surrounding the outer perimeter 138 of the first electrode 106 and the outer perimeter 160 of the second electrode 108. In some embodiments, the first film layer 122 is heat sealed to the second film layer 124. Specifically, in some embodiments, the first film layer 122 is sealed to the second film layer 124 to define a sealed portion 190 that surrounds the first electrode 106 and the second electrode 108. The first film layer 122 and the second film layer 124 may be sealed in any suitable manner, such as using an adhesive, heat sealing, or the like.

[0024] The first electrode 106, the second electrode 108, the first electrical insulator layer 111, and the second electrical insulator layer 112 provide a barrier that prevents the first film layer 122 from sealing to the second film layer 124, forming an unsealed portion 192. The unsealed portion 192 of the housing 110 includes an electrode region 194 where the electrode pair 104 is provided, and an expandable fluid region 196 that is surrounded by the electrode region 194. The central openings 146, 168 of the first electrode 106 and the second electrode 108 form the expandable fluid region 196 and are arranged to be axially stacked relative to each other. Although not shown, the housing 110 can be cut to fit the geometry of the electrode pair 104 and to reduce the size of the artificial muscle 100, i.e., the size of the sealed portion 190.

[0025] A dielectric fluid 198 is provided within the unsealed portion 192 and flows freely between the first electrode 106 and the second electrode 108. A "dielectric" fluid, as used herein, is a medium or substance that transmits electrical force without conduction, and as such, has low electrical conductivity. Some non-limiting example dielectric fluids include perfluoroalkanes, transformer oil, and deionized water. It should be understood that the dielectric fluid 198 can be injected into the unsealed portion 192 of the artificial muscle 100 using a needle or other suitable injection device.

[0026] 3A and 3B, the artificial muscle 100 is actuable between an unactuated state and an actuated state. In the unactuated state, the first electrode 106 and the second electrode 108 are partially spaced from each other proximate their central openings 146, 168 and the first ends 134, 156 of the tab portions 132, 154, as shown in FIG. 3A. The second ends 136, 158 of the tab portions 132, 154 remain in place relative to each other due to the housing 110 being sealed at the outer periphery 138 of the first electrode 106 and the outer periphery 160 of the second electrode 108. In the actuated state, the first electrode 106 and the second electrode 108 are in contact with each other and oriented parallel to each other, forcing a dielectric fluid 198 into the expandable fluid region 196, as shown in FIG. 3B. This causes the dielectric fluid 198 to flow through the central openings 146, 168 of the first electrode 106 and the second electrode 108, causing the expandable fluid region 196 to expand.

[0027] 3A , the artificial muscle 100 is shown in an unactuated state. The electrode pair 104 is provided within an electrode region 194 of an unsealed portion 192 of the housing 110. The central opening 146 of the first electrode 106 and the central opening 168 of the second electrode 108 are coaxially aligned within the expandable fluid region 196. In the unactuated state, the first electrode 106 and the second electrode 108 are partially spaced apart from each other and non-parallel to each other. Due to the first film layer 122 being sealed to the second film layer 124 around the electrode pair 104, the second ends 136, 158 of the tab portions 132, 154 are in contact with each other. Thus, the dielectric fluid 198 is provided between the first electrode 106 and the second electrode 108, thereby separating the first ends 134, 156 of the tab portions 132, 154 proximal to the expandable fluid region 196. In other words, the distance between the first end 134 of the tab portion 132 of the first electrode 106 and the first end 156 of the tab portion 154 of the second electrode 108 is greater than the distance between the second end 136 of the tab portion 132 of the first electrode 106 and the second end 158 of the tab portion 154 of the second electrode 108. This results in the electrode pair 104 zipping toward the expandable fluid region 196 when actuated. In some embodiments, the first electrode 106 and the second electrode 108 can be flexible. 3A, the first electrode 106 and the second electrode 108 are convex such that the second ends 136, 158 of their tab portions 132, 154 may remain close to each other but are spaced apart from each other proximal to the central openings 146, 168. In the unactuated state, the expandable fluid region 196 has a first height H1.

[0028] When actuated, as shown in FIG. 3B , the first electrode 106 and the second electrode 108 zip toward each other from the second ends 144, 158 of their tab portions 132, 154, thereby forcing the dielectric fluid 198 into the expandable fluid region 196. As shown, in the actuated state, the first electrode 106 and the second electrode 108 are parallel to each other. In the actuated state, the dielectric fluid 198 flows into the expandable fluid region 196, causing it to expand. As such, the first film layer 122 and the second film layer 124 expand in opposite directions. In the actuated state, the expandable fluid region 196 has a second height H2, which is greater than the first height H1 of the expandable fluid region 196 when in the unactuated state. Note that, although not shown, the electrode pair 104 can be partially actuated to a position between the unactuated and actuated states. This allows for partial expansion and adjustment of the expandable fluid region 196 as needed.

[0029] A voltage is applied by a power source (such as power source 48 in FIG. 7 ) to move the first electrode 106 and the second electrode 108 toward each other. In some embodiments, a voltage of up to 10 kV can be provided from the power source to induce an electric field through the dielectric fluid 198. The resulting attractive force between the first electrode 106 and the second electrode 108 forces the dielectric fluid 198 into the expandable fluid region 196. Pressure from the dielectric fluid 198 within the expandable fluid region 196 causes the first film layer 122 and the first electrical insulator layer 111 to deform in a first axial direction along the central axis C of the first electrode 106 and the second film layer 124 and the second electrical insulator layer 112 to deform in an opposite second axial direction along the central axis C of the second electrode 108. When the voltage supplied to the first electrode 106 and the second electrode 108 is discontinued, the first electrode 106 and the second electrode 108 return to their initial non-parallel position in the unactuated state. In operation, a voltage can be applied to one or more artificial muscles 100 of the artificial muscle stacks 201, 301, 301' of Figures 5A-7 to collectively and / or selectively actuate the artificial muscles 100 of the artificial muscle stacks 201, 301, 301'.

[0030] The artificial muscle 100 disclosed herein, and specifically this embodiment of the tab portions 132, 154 with interconnecting bridge portions 174, 176, offers several improvements over actuators that do not include tab portions 132, 154, such as the hydraulically amplified self-healing electrostatic (HASEL) actuators described in the paper entitled “Hydraulically amplified self-healing electrostatic actuators with muscle-like performance” by E. Acome, S.K. Mitchell, T.G. Morrissey, M.B. Emmett, C. Benjamin, M. King, M. Radakovitz, and C. Keplinger (Science 05 Jan 2018: Vol. 359, Issue 6371, pp. 61-65). An embodiment of the artificial muscle 100 that includes two pairs of tab portions 132, 154 on each of the first electrode 106 and the second electrode 108, respectively, reduces the overall mass and thickness of the artificial muscle 100, reduces the amount of voltage required during actuation, and reduces the total volume of the artificial muscle 101 without reducing the amount of resulting force after actuation compared to known HASEL actuators that include donut-shaped electrodes with uniform radially extending widths. More specifically, the tab portions 132, 154 of the artificial muscle 100 provide a zipping front that results in increased actuation power by providing localized and uniform hydraulic actuation of the artificial muscle 100 compared to HASEL actuators that include donut-shaped electrodes. Specifically, a pair of tab portions 132, 154 provides twice the amount of actuator power per unit volume compared to a donut-shaped HASEL actuator, while two pairs of tab portions 132, 154 provide four times the amount of actuator power per unit volume. The bridge portions 174, 176 interconnecting the tab portions 132, 154 also limit buckling of the tab portions 132, 154 by maintaining the distance between adjacent tab portions 132, 154 during actuation.Because the bridge portions 174, 176 are integrally formed with the tab portions 132, 154, the bridge portions 174, 176 also prevent leakage between the tab portions 132, 154 by eliminating adhesion points that present an increased risk of blockage.

[0031] In operation, when the artificial muscle 100 is actuated, the expansion of the expandable fluid region 196 increases by cubic centimeters (cm) of actuator volume. 3 ) force of 3 Newton millimeters (N.mm) or more per cm 3 4N.mm or more per cm 3 5N.mm or more per cm 3 6N.mm or more per cm 3 7N.mm or more per cm 3 Such as 8 N.mm or more per 100 gram load, or the like. In one example, when the artificial muscle 100 is actuated with a voltage of 9.5 kilovolts (kV), the artificial muscle 100 produces a resultant force of 5 N. In another example, when the artificial muscle 100 is actuated with a voltage of 10 kV, the artificial muscle 100 produces a 440% strain at a 500 gram load.

[0032] Furthermore, the size of the first electrode 106 and the second electrode 108 is proportional to the amount of displacement of the dielectric fluid 198. Thus, the greater the displacement desired within the expandable fluid region 196, the greater the size of the electrode pair 104 is increased relative to the size of the expandable fluid region 196. It should be understood that the size of the expandable fluid region 196 is defined by the central openings 146, 168 in the first electrode 106 and the second electrode 108. Thus, the degree of displacement within the expandable fluid region 196 can alternatively or additionally be controlled by increasing or decreasing the size of the central openings 146, 168.

[0033] As shown in FIGS. 4A and 4B, another embodiment of an artificial muscle 100′ is illustrated. Artificial muscle 100′ is substantially similar to artificial muscle 100. As such, like structures are indicated with like reference numbers. However, as shown, first electrode 106 does not include a central opening. Thus, only second electrode 108 includes central opening 168 formed therein. As shown in FIG. 8, artificial muscle 100′ is in an unactuated state with first electrode 106 being flat and second electrode 108 being convex relative to first electrode 106. In the unactuated state, expandable fluid region 196 has a first height H3. In the actuated state, as shown in FIG. 4B, expandable fluid region 196 has a second height H4 that is greater than first height H3. It should be understood that by providing the central opening 168 only in the second electrode 108, as opposed to both the first electrode 106 and the second electrode 108, a global deformation can be formed on one side of the artificial muscle 100'. Additionally, because a global deformation is formed on only one side of the artificial muscle 100', the second height H4 of the expandable fluid region 196 of the artificial muscle 100' extends farther from the longitudinal axis perpendicular to the central axis C of the artificial muscle 100' than the second height H2 of the expandable fluid region 196 of the artificial muscle 100, all other dimensions, orientation, and volume of the dielectric fluid being the same.

[0034] 5A-7, artificial muscle stacks 201, 301, 301' are depicted. In FIGS. 5A-7, each artificial muscle stack 201, 301, 301' comprises multiple artificial muscle layers 210, 310, each of the multiple artificial muscle layers 210, 310 comprising one or more artificial muscles 100. In some embodiments, the multiple artificial muscle layers alternatively or additionally comprise the artificial muscle 100' of FIGS. 4A and 4B. In operation, the artificial muscle stacks 201, 301, 301' generate more actuation force than a single artificial muscle 100. FIGS. 5A-7 depict several different stack arrangements that can be used to generate increased actuation force.

[0035] The artificial muscle stack 201 of FIGS. 5A-5C comprises multiple artificial muscle layers 210 arranged in coaxial alignment, such that the expandable fluid region 196 of each individual artificial muscle 100 in an individual artificial muscle layer 210 is in coaxial alignment with an individual artificial muscle 100 in another individual artificial muscle layer 210. As shown in the side views of FIGS. 5B and 5C, the artificial muscle stack 201 comprises three artificial muscle layers 210A-210C. It should be understood that any number of artificial muscle layers 210 is contemplated. FIG. 5B depicts the artificial muscle stack 201 in an unactuated state, and FIG. 5C depicts the artificial muscle stack 201 in an actuated state. In each layer of the artificial muscle stack 201, there are no overlapping individual artificial muscles 100. Thus, while the artificial muscle stack 201 of FIGS. 5A-5B can generate a collective actuation force, the coaxial alignment of the individual artificial muscles 100 in each artificial muscle layer 210 creates a large footprint. To reduce the footprint of an artificial muscle arrangement, an artificial muscle stack 301 depicted in Figures 6A-6E can be implemented.

[0036] The artificial muscle stack 301 in Figures 6A-6E includes multiple artificial muscle layers 310 arranged in an alternating offset configuration. The artificial muscle stack 301 includes four artificial muscle layers 310: a first artificial muscle layer 310A, a second artificial muscle layer 310B, a third artificial muscle layer 310C, and a fourth artificial muscle layer 310D. Figure 6A is a top view of the artificial muscle stack 301, and Figures 6B-6E are side views of the artificial muscle stack 301. Figures 6B and 6C show side views of the artificial muscle stack 301 along line 6B-6B in the unactuated state (Figure 6B) and the actuated state (Figure 6C). Figures 6D and 6E show side views of the artificial muscle stack 301 along line 6D-6D in the unactuated state (Figure 6D) and the actuated state (Figure 6E). Line 6B-6B is orthogonal to line 6D-6D; thus, FIGS. 6B and 6C show a different side of artificial muscle stack 301 than FIGS. 6D and 6E, and the side shown by FIGS. 6B and 6C is orthogonal to the side shown by FIGS. 6D and 6E.

[0037] Each artificial muscle layer 310 comprises one or more artificial muscles 100, e.g., multiple artificial muscles 100. For example, in FIG. 6A , the first artificial muscle 100A is illustrative of an artificial muscle 100 in the artificial muscle stack 301. It should be understood that embodiments are contemplated in which some of the artificial muscle layers 310 in the artificial muscle stack 301 comprise a single artificial muscle 100. In the alternating offset arrangement of the artificial muscle stack 301 depicted in FIGS. 6A-6E , the multiple artificial muscle layers 310 are arranged such that each expandable fluid region 196 of the housing 110 of one or more artificial muscles 100 in each artificial muscle layer 310 overlaps at least one tab portion 132, 154 of one or more artificial muscles 100 in an adjacent artificial muscle layer 310. In other words, each expandable fluid region 196 of the housing 110 of one or more artificial muscles 100 in each artificial muscle layer 310 overlaps the electrode region 194 of the housing 110 of one or more artificial muscles 100 in an adjacent artificial muscle layer 310. In some embodiments, an individual tab portion 132, 154 of one artificial muscle 100 can overlap the expandable fluid region 196 of an artificial muscle 100 in an adjacent artificial muscle layer 310 such that the second end 136, 158 of the individual tab portion 132, 154 terminates at or near the central axis C of the expandable fluid region 196 of the artificial muscle 100 in the adjacent muscle layer 310. Thus, some of the expandable fluid regions 196 can be overlapped by two tab portions 132, 154, each from a different artificial muscle 100, on one or both sides of the expandable fluid region 196. Although the tab portion 154 of the second electrode 108 of the electrode pair 104 is shown in FIG. 6A, it should be understood that the electrode pair 104 also includes the first electrode 106 with the tab portion 132 .

[0038] 6A to 6E, to illustrate the alternately offset arrangement of the artificial muscle stacks 301, the relative line thickness of the artificial muscles 100 in each artificial muscle layer 310 is used to illustrate the relative spatial positioning of each artificial muscle layer 310. For example, in FIG. 6A, the first artificial muscle layer 310A is the top layer, so the artificial muscles 100 in the first artificial muscle layer 310A are depicted with the widest line thickness of the multiple artificial muscle layers 310. Similarly, in FIG. 6A, the fourth artificial muscle layer 310D is the bottom layer, so the artificial muscles 100 in the fourth artificial muscle layer 310D are depicted with the narrowest line thickness of the multiple artificial muscle layers 310.

[0039] In an alternating offset arrangement of the artificial muscle stack 301, adjacent artificial muscle layers 310 of the artificial muscle stack 301 are offset from one another along one or more tab axes, such as first tab axis 10 or second tab axis 12. Each tab axis extends from a central axis C of the expandable fluid region 196 of an individual artificial muscle 100 in the plurality of artificial muscle layers 310 to at least one end (i.e., second end 136, 158) of the tab portions 132, 154 of an individual artificial muscle 100 in the plurality of artificial muscle layers 310. Because the embodiments of the artificial muscles 100 of the artificial muscle stack 301 depicted in FIGS. 6A-6E each include four tab portions 132, 154 arranged in diametrically opposed pairs, the first tab axis 10 is perpendicular to the second tab axis 12. It should be understood that while the artificial muscles 100 of the artificial muscle stack 310 include four tab portions 132, 154 (i.e., each electrode of the electrode pair 104 of each artificial muscle 100 includes four tab portions 132, 154), embodiments are contemplated with artificial muscles 100 including more or fewer than four tab portions 132, 154. These embodiments may include more than two tab axes, such as embodiments with three tab portions per electrode, five tab portions per electrode, or six tab portions per electrode, or only a single tab axis, such as embodiments with a single pair of diametrically opposed tab portions. Furthermore, it should be understood that embodiments are contemplated in which other artificial muscle designs are arranged in an alternating offset configuration, such as, for example, triangular or rectangular artificial muscles.

[0040] Still referring to FIGS. 6A-6E , embodiments of the artificial muscle stack 301 with at least three artificial muscle layers 310 include at least one inner artificial muscle layer 310 that is adjacent to two other artificial muscle layers 310. In these embodiments, each inner artificial muscle layer is offset from its first adjacent artificial muscle layer along a first tab axis 10 and from its second adjacent artificial muscle layer along a second tab axis 12. This multi-axial offset is depicted in the side views of FIGS. 6B-6E by a lateral shift indicating the offset along one tab axis and by relative line thickness indicating the offset along the other tab axis. In FIGS. 6B and 6C , the offset between the artificial muscle layers 310 along the second tab axis 12 is indicated by the lateral shift, and the offset between adjacent artificial muscle layers 310 along the first tab axis 10 is indicated by the relative line thickness. In particular, the wider line thickness in Figures 6B and 6C shows the artificial muscle layer 310 shifted to the foreground (i.e., off the page) along the first tab axis 10, and the narrower line thickness in Figures 6B and 6C shows the artificial muscle layer 310 shifted to the background (i.e., into the page) along the first tab axis 10. In Figures 6D and 6E, the offset between the artificial muscle layers 310 along the first tab axis 10 is indicated by the lateral shift, and the offset between adjacent artificial muscle layers 310 along the second tab axis 12 is indicated by the relative line thickness. In particular, the wider line thickness in Figures 6D and 6E shows the artificial muscle layer 310 shifted to the foreground (i.e., off the page) along the second tab axis 12, and the narrower line thickness in Figures 6D and 6E shows the artificial muscle layer 310 shifted to the background (i.e., into the page) along the second tab axis 12.

[0041] 6A-6E, the second artificial muscle layer 310B and the third artificial muscle layer 310C are inner artificial muscle layers. The second artificial muscle layer 310B is offset from the first artificial muscle layer 310A along the first tab axis 10 and from the third artificial muscle layer 310C along the second tab axis 12. The third artificial muscle layer 310C is offset from the second artificial muscle layer 310B along the second tab axis 12 and from the fourth artificial muscle layer 310D along the first tab axis 10. This pattern can be repeated in an artificial muscle stack 301 with an increased number of artificial muscle layers 310, allowing for a densely stacked arrangement of artificial muscle layers.

[0042] 6A-6E , the overlap of the tab portions 132, 154 and expandable fluid regions 196 in adjacent artificial muscle layers 310 in an alternating offset arrangement of the artificial muscle stack 301 allows an increased number of artificial muscles 100 to be disposed within a particular footprint when compared to the artificial muscle stack 201 of FIGS. 5A-5C . In fact, the artificial muscle stack 301 maximizes the number of artificial muscles 100 that can be disposed in a particular footprint, both laterally (i.e., along the first and second tab axes 10, 12) and in depth, maximizing the collective actuation force per unit volume of the artificial muscle stack 301. As each artificial muscle 100 is actuated, the tab portions 132, 154 of the electrode pairs 104 move closer together (e.g., flatten), and the expandable fluid regions 196 expand. Because the tab portions 132, 154 flatten, the expandable fluid region 196 of an artificial muscle 100 can be positioned above and / or below the tab portions of adjacent artificial muscle layers 310. This allows an increased number of artificial muscles to be positioned together in a condensed block (i.e., the artificial muscle stack 301) and operate in concert. In fact, the artificial muscle stack 301 is designed so that the artificial muscles 100 in each artificial muscle layer 310 can exert their collective force in an additive manner. Conversely, the coaxial alignment of the artificial muscle stack 201 in FIG. 5A limits the additive force generated by each artificial muscle layer 210 because the expandable fluid regions 196 of each artificial muscle layer 210 overlap.

[0043] Referring now to FIG. 7, an artificial muscle stack 301′ is depicted. The artificial muscle stack 301′ comprises the artificial muscle stack 301 of FIGS. 6A-6E with the addition of peripheral artificial muscles 315. The peripheral artificial muscles 315 comprise the same structure as the artificial muscles 100, but have fewer tab portions 132, 154 than the artificial muscles 100 of the artificial muscle stack 301′, as shown by the first peripheral artificial muscle 315A. As shown in FIG. 7, the artificial muscles 100 of the artificial muscle stack 301′ comprise four tab portions 132, 154, while the peripheral artificial muscles 315 comprise two or three tab portions 132, 154. In particular, the peripheral artificial muscles 315 can comprise edge peripheral artificial muscles 316 and corner peripheral artificial muscles 318. The edge-periphery artificial muscles 316 extend along a single side of the artificial muscle stack 301, and the corner-periphery artificial muscles 318 are disposed at the corners of the artificial muscle stack 301 such that one tab portion of the corner-periphery artificial muscles 318 extends along one side of the artificial muscle stack 301 and another tab of the corner-periphery artificial muscles 318 extends along another side of the artificial muscle stack 301.

[0044] 6A-6E, the alternating offset arrangement of the multiple artificial muscle layers 310 in the artificial muscle stack 301 creates a symmetric imbalance along the edges of the artificial muscle stack 301. That is, due to the alternating offset arrangement, the artificial muscle layers 310 may terminate laterally in different locations, leaving edge gaps in the artificial muscle stack 301. As shown in FIG. 7, peripheral artificial muscles 315 may be used to fill these edge gaps so that each artificial muscle layer 310 in the artificial muscle stack 301' is laterally adjacent. In some embodiments, each artificial muscle layer 310 may comprise a combination of peripheral artificial muscles 315, e.g., edge peripheral artificial muscles 316 and corner peripheral artificial muscles 318, to both balance the symmetry along the edges of the artificial muscle stack 301 and to add additional actuation force to the artificial muscle stack 301 without increasing its overall footprint.

[0045] 8, an actuation system 400 can be provided to operate each individual artificial muscle 100 in the artificial muscle stacks 201, 301, 301′. The actuation system 400 can include a controller 50, an operating device 46, a power source 48, a display device 42, network interface hardware 44, and a communication path 41 communicatively coupling these components.

[0046] The controller 50 includes a processor 52 and a non-transitory electronic memory 54, with various components communicatively coupled. In some embodiments, the processor 52, the non-transitory electronic memory 54, and / or other components are contained within a single device. In other embodiments, the processor 52, the non-transitory electronic memory 54, and / or other components may be distributed among multiple communicatively coupled devices. The controller 50 includes a non-transitory electronic memory 54 that stores a set of machine-readable instructions. The processor 52 executes the machine-readable instructions stored in the non-transitory electronic memory 54. The non-transitory electronic memory 54 may comprise RAM, ROM, flash memory, a hard drive, or any device capable of storing machine-readable instructions such that the machine-readable instructions can be accessed by the processor 52. Accordingly, the operating system 400 described herein may be implemented in any conventional computer programming language, as a pre-programmed hardware element, or as a combination of hardware and software components. The non-transitory electronic memory 54 may be implemented as a single memory module or multiple memory modules.

[0047] In some embodiments, the non-transitory electronic memory 54 includes instructions for performing the functions of the actuation system 400. The instructions can include instructions for operating the artificial muscle stacks 201, 301, 301′, such as for actuating one or more artificial muscles 100, individually or collectively, and for actuating the artificial muscle layers 210, 310, individually or collectively.

[0048] The processor 52 may be any device capable of executing machine-readable instructions. For example, the processor 52 may be an integrated circuit, a microchip, a computer, or any other computing device. The non-transitory electronic memory 54 and the processor 52 are coupled to a communication path 41 that provides signal interconnectivity between various components and / or modules of the operating system 400. Thus, the communication path 41 may communicatively couple any number of processors to each other, enabling the modules coupled to the communication path 41 to operate in a distributed computing environment. Specifically, each of the modules may operate as a node that can transmit and / or receive data. As used herein, the term "communicatively coupled" means that the coupled components can exchange data signals with each other, such as, for example, electrical signals through a conductive medium, electromagnetic signals through the air, optical signals through an optical waveguide, and the like.

[0049] 8, communication path 41 communicatively couples processor 52 and non-transitory electronic memory 54 of controller 50 to several other components of operating system 400. For example, operating system 400 depicted in FIG. 8 includes processor 52 and non-transitory electronic memory 54 communicatively coupled to operating device 46 and power source 48.

[0050] The operating device 46 allows a user to control the operation of the artificial muscles 100 of the artificial muscle stack 201, 301, 301'. In some embodiments, the operating device 46 can be a switch, a toggle, a button, or any combination of controls for providing user action. The operating device 46 is coupled to the communication path 41 such that the communication path 41 communicatively couples the operating device 46 to other modules of the actuation system 400. The operating device 46 can provide a user interface for receiving user commands regarding a particular operational configuration of the artificial muscle stack 201, 301, 301'.

[0051] A power source 48 (e.g., a battery) provides power to one or more artificial muscles 100 of the artificial muscle stacks 201, 301, 301'. In some embodiments, the power source 48 is a rechargeable DC power source. It should be understood that the power source 48 can be a single power source or battery for providing power to one or more artificial muscles 100 of the artificial muscle stacks 201, 301, 301'. A power adapter (not shown) can be provided and electrically coupled via a wiring harness or the like for providing power to one or more artificial muscles 100 of the artificial muscle stacks 201, 301, 301' via the power source 48.

[0052] In some embodiments, the actuation system 400 also includes a display device 42. The display device 42 is coupled to the communication path 41 such that the communication path 41 communicatively couples the display device 42 to other modules of the actuation system 400. In addition to providing optical information, the display device 42 may be a touchscreen that detects the presence and location of tactile input on a surface of the display device 42 or a surface adjacent to the display device 42. Thus, the display device 42 may include an operating device 46 and receive mechanical input directly when optical output is provided by the display device 42.

[0053] In some embodiments, the actuation system 400 includes network interface hardware 44 for communicatively coupling the actuation system 400 to a portable device 70 via a network 60. The portable device 70 may include, but is not limited to, a smartphone, a tablet, a personal media player, or any other electronic device that includes wireless communication capabilities. It should be understood that, if provided, the portable device 70 may serve to provide user commands to the controller 50 instead of the operating device 46. As such, a user may be able to control or set programs for controlling the artificial muscles 100 of the artificial muscle stacks 201, 301, 301′ utilizing control of the operating device 46. Thus, the artificial muscles 100 of the artificial muscle stacks 201, 301, 301′ may be remotely controlled via the portable device 70, which communicates wirelessly with the controller 50 via the network 60.

[0054] It should be understood here that embodiments described herein are directed to artificial muscle stacks comprising multiple artificial muscle layers stacked in an alternating offset arrangement such that each expandable fluid region of one or more artificial muscles of each artificial muscle layer overlaps at least one tab portion of one or more artificial muscles of an adjacent artificial muscle layer. This alternating offset arrangement increases the number of artificial muscles that can be arranged in a given footprint to form a small footprint artificial muscle stack that can achieve a large actuation force per unit volume of the artificial muscle stack.

[0055] It should be noted that the terms "substantially" and "about" may be used herein to express the inherent degree of uncertainty that may result from any quantitative comparison, value, measurement, or other representation. These terms are also used herein to express the degree to which a quantitative representation may vary from the stated reference without resulting in a change in the basic functionality of the subject matter at issue.

[0056] While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications can be made without departing from the scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.

Claims

1. An artificial muscle stack comprising a plurality of artificial muscle layers, each artificial muscle layer comprises one or more artificial muscles; The one or more artificial muscles include: a housing having an electrode region and an expandable fluid region; a dielectric fluid contained within the housing; an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; Equipped with the first electrode and the second electrode each include two or more tab portions and two or more bridge portions; each of the two or more bridge portions interconnecting adjacent tab portions; at least one of the first electrode and the second electrode is positioned between the two or more tab portions and includes a central opening that circumscribes the expandable fluid region; the plurality of artificial muscle layers are arranged such that the expandable fluid region of the one or more artificial muscles of each artificial muscle layer overlaps at least one tab portion of one or more artificial muscles of an adjacent artificial muscle layer; Artificial muscle stack.

2. 10. The artificial muscle stack of claim 1, wherein adjacent artificial muscle layers are offset from one another along one or more tab axes, each tab axis extending from a central axis of the expandable fluid region of an individual artificial muscle of the plurality of artificial muscle layers to an end of at least one of the two or more tab portions of the individual artificial muscle of the plurality of artificial muscle layers.

3. 3. The artificial muscle stack of claim 2, wherein the plurality of artificial muscle layers comprises at least three artificial muscle layers, each inner artificial muscle layer offset from a first adjacent artificial muscle layer along a first tab axis and offset from a second adjacent artificial muscle layer along a second tab axis.

4. 4. The artificial muscle stack of claim 3, wherein the first tab axis is perpendicular to the second tab axis.

5. At least one of the plurality of artificial muscle layers further comprises one or more peripheral artificial muscles; 10. The artificial muscle stack of claim 1, wherein the one or more peripheral artificial muscles comprise fewer tab portions than at least other artificial muscles of the plurality of artificial muscle layers.

6. 10. The artificial muscle stack of claim 1, wherein each of the plurality of artificial muscle layers comprises a plurality of artificial muscles.

7. 10. The artificial muscle stack of claim 1, wherein the first electrode and the second electrode each include two pairs of tab portions and two pairs of bridge portions, each bridge portion adjacent to and interconnecting a pair of adjacent tab portions, and each tab portion diametrically opposed to an opposing tab portion.

8. 10. The artificial muscle stack of claim 1, wherein the first electrode is fixed to a first surface of the housing and the second electrode is fixed to a second surface of the housing.

9. 10. The artificial muscle stack of claim 1, wherein the electrode pairs are actuable between an unactuated state and an actuated state such that actuation from the unactuated state to the actuated state directs the dielectric fluid into the expandable fluid region, expanding the expandable fluid region.

10. when the electrode pair is in the unactuated state, the first electrode and the second electrode are non-parallel to one another; 10. The artificial muscle stack of claim 9, wherein when the electrode pair is in the actuated state, the first electrode and the second electrode are parallel to each other such that the first electrode and the second electrode are configured to zip toward each other and toward the central opening when actuated from the unactuated state to the actuated state.

11. 10. The artificial muscle laminate of claim 1, further comprising a first electrical insulator layer secured to an inner surface of the first electrode opposite a first side of the housing, and a second electrical insulator layer secured to an inner surface of the second electrode opposite a second side of the housing, the first electrical insulator layer and the second electrical insulator layer each including an adhesive surface and an opposite non-sealing surface.

12. An artificial muscle stack comprising three or more artificial muscle layers, each artificial muscle layer comprises one or more artificial muscles; The one or more artificial muscles include: a housing having an electrode region and an expandable fluid region; a dielectric fluid contained within the housing; an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; Equipped with the first electrode and the second electrode each include two or more tab portions and two or more bridge portions; each of the two or more bridge portions interconnecting adjacent tab portions; at least one of the first electrode and the second electrode is positioned between the two or more tab portions and includes a central opening that circumscribes the expandable fluid region; each inner artificial muscle layer is offset from a first adjacent artificial muscle layer along a first tab axis and from a second adjacent artificial muscle layer along a second tab axis; each tab axis extends from a central axis of the expandable fluid region to an end of at least one of the two or more tab portions of the one or more artificial muscles of the inner artificial muscle layer; Artificial muscle stack.

13. 13. The artificial muscle stack of claim 12, wherein the first tab axis is perpendicular to the second tab axis.

14. 13. The artificial muscle stack of claim 12, wherein the electrode pairs are actuable between an unactuated state and an actuated state such that actuation from the unactuated state to the actuated state directs the dielectric fluid into the expandable fluid region, expanding the expandable fluid region.

15. 13. The artificial muscle stack of claim 12, wherein the first electrode is fixed to a first surface of the housing and the second electrode is fixed to a second surface of the housing.

16. 13. The artificial muscle stack of claim 12, wherein each of the three or more artificial muscle layers comprises a plurality of artificial muscles.

17. 1. A method for actuating an artificial muscle stack, comprising: generating a voltage using a power source electrically coupled to an electrode pair of each artificial muscle of the plurality of artificial muscle layers; Each artificial muscle comprises a housing having an electrode region and an expandable fluid region; The dielectric fluid is contained within the housing; the electrode pair includes a first electrode and a second electrode and is positioned in the electrode region of the housing; the first electrode and the second electrode each include two or more tab portions and two or more bridge portions; each of the two or more bridge portions interconnecting adjacent tab portions; generating a voltage, wherein at least one of the first electrode and the second electrode is positioned between two or more tab portions and includes a central opening that circumscribes the expandable fluid region, and the plurality of artificial muscle layers are arranged such that the expandable fluid region of each artificial muscle of each artificial muscle layer overlaps at least one tab portion of one or more artificial muscles of an adjacent artificial muscle layer; applying the voltage to the electrode pair of at least one artificial muscle of at least one of the plurality of artificial muscle layers, thereby actuating the electrode pair of the at least one artificial muscle from an unactuated state to an actuated state, such that a dielectric fluid is directed into the expandable fluid region of the housing and expands the expandable fluid region; A method comprising:

18. 18. The method of claim 17, wherein adjacent artificial muscle layers are offset from one another along one or more tab axes, each tab axis extending from a central axis of the expandable fluid region of an individual artificial muscle of the plurality of artificial muscle layers to an end of at least one of the two or more tab portions of the individual artificial muscle of the plurality of artificial muscle layers.

19. 19. The method of claim 18, wherein the plurality of artificial muscle layers comprises at least three artificial muscle layers, each inner artificial muscle layer offset from a first adjacent artificial muscle layer along a first tab axis and offset from a second adjacent artificial muscle layer along a second tab axis.

20. 18. The method of claim 17, further comprising applying the voltage to the electrode pair of each artificial muscle in each of the plurality of artificial muscle layers, thereby actuating the electrode pair of each artificial muscle from the unactuated state to the actuated state, such that the dielectric fluid is directed into an expandable fluid region of the housing of each artificial muscle and expands the expandable fluid region of each artificial muscle.

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