Artificial muscle stack comprising alternatingly biased artificial muscle layers

Abstract

An artificial muscle stack includes multiple artificial muscle layers. Each artificial muscle layer includes one or more artificial muscles, each artificial muscle including a shell having an electrode area and an expandable fluid area, a dielectric fluid contained in the shell, and an electrode pair having first and second electrodes located in the electrode area. The first electrode and the second electrode each include two or more tab portions and two or more bridging portions. The two or more bridging portions interconnect adjacent tab portions. At least one of the first and second electrodes includes a central opening located between the tab portions and surrounding the expandable fluid area. The multiple artificial muscle layers are arranged so that the expandable fluid area of ​​the 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.

Description

Technical Field

[0001] This description generally relates to stacking and arrangement of artificial muscles. Background Art

[0002] Current robotics often rely on rigid components, such as servo motors, to perform tasks in a structured environment. This rigidity presents limitations in many robotic applications, at least in part due to the weight-to-power ratio of servo motors and other rigid robotic devices. The field of soft robotics has addressed these limitations through the use of artificial muscles and other soft actuators. Artificial muscles attempt to mimic the versatility, performance, and reliability of biological muscles. Some artificial muscles rely on fluid actuators, but fluid actuators require a supply of pressurized gas or liquid, and the fluid transport must be carried out through a system of channels and tubing, which limits the speed and efficiency of the artificial muscle. Other artificial muscles use heat-activated polymer fibers, but these fibers are difficult to control and have low efficiency.

[0003] A specific artificial muscle design is described in a paper by E. Acome, SK Mitchell, TG Morrissey, MBEmmett, C. Benjamin, M. King, M. Radakovitz, and C. Keplinger titled "Hydraulically Amplified Self-Healing Electrostatic Actuator with Muscle-Like Performance" (Science, January 5, 2018: Vol. 359, No. 6371, pp. 61-65). This hydraulically amplified self-healing electrostatic (HASEL) actuator uses electrostatic and hydraulic forces to achieve various actuation modes. However, the actuator power per unit volume of the HASEL actuator artificial muscle is limited. In addition, the HASEL actuator artificial muscle and other known artificial muscles are difficult to combine in a small footprint while increasing the achievable collective force of these artificial muscle combinations.

[0004] Therefore, there is a need for improved artificial muscles having increased actuator power per unit volume and for 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, and the one or more artificial muscles include a shell having an electrode area and an expandable fluid area, a dielectric fluid contained in the shell, and an electrode pair having a first electrode and a second electrode located in the electrode area of ​​the shell. The first electrode and the second electrode each include two or more tab portions and two or more bridging portions. Each of the two or more bridging portions interconnects adjacent tab portions. At least one of the first electrode and the second electrode includes a central opening located between the two or more tab portions and surrounding the expandable fluid area. In addition, the multiple artificial muscle layers are arranged so that the expandable fluid area of ​​one or more artificial muscles of each artificial muscle layer overlaps with at least one tab portion of one or more artificial muscles of an adjacent artificial muscle layer.

[0006] In another embodiment, an 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 shell having an electrode area and an expandable fluid area, a dielectric fluid contained in the shell, and an electrode pair including a first electrode and a second electrode located in the electrode area of ​​the shell. The first electrode and the second electrode each include two or more tab portions and two or more bridging portions. Each of the two or more bridging portions interconnects adjacent tab portions. At least one of the first electrode and the second electrode includes a central opening located between the two or more tab portions and surrounding the expandable fluid area. In addition, each inner artificial muscle layer is offset along a first tab axis relative to the first adjacent artificial muscle layer and offset along a second tab axis relative to the second adjacent artificial muscle layer, wherein each tab axis extends from the central axis of the expandable fluid area to the end of at least one tab portion of the one or more artificial muscles of the inner artificial muscle layer.

[0007] In another embodiment, a method for actuating an artificial muscle stack includes generating a voltage using a power supply electrically coupled to an electrode pair of each artificial muscle in a plurality of artificial muscle layers. Each artificial muscle includes a housing having an electrode region and an expandable fluid region, a dielectric fluid contained within the housing, and the electrode pair including a first electrode and a second electrode located 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 bridging portions, each of the two or more bridging portions interconnecting adjacent tab portions, and at least one of the first electrode and the second electrode includes a central opening located between the two or more tab portions and surrounding the expandable fluid region. The plurality of artificial muscle layers are arranged such that the expandable fluid region of each artificial muscle in each artificial muscle layer overlaps at least one tab portion of one or more artificial muscles in an adjacent artificial muscle layer. The method further includes applying a voltage to the electrode pair of at least one artificial muscle in at least one of the plurality of artificial muscle layers, thereby actuating the electrode pair of the at least one artificial muscle from a non-actuated state to an actuated state, causing the dielectric fluid to be directed into the expandable fluid region of the housing and causing the expandable fluid region to expand.

[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 accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] 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 these illustrative embodiments can be understood when read in conjunction with the following drawings, in which like structures are represented by like reference numerals, wherein:

[0010] Figure 1 schematically depicts an exploded view of an illustrative artificial muscle according to one or more embodiments shown and described herein;

[0011] Figure 2 Schematically depicts a schematic diagram of a system according to one or more embodiments shown and described herein. Figure 1 A top view of the artificial muscle;

[0012] Figure 3A Schematically depicts a non-actuated state according to one or more embodiments shown and described herein. Figure 1 and Figure 2 Artificial muscles along Figure 2 A cross-sectional view taken along line 3-3 in FIG.

[0013] Figure 3B Schematically depicts a schematic diagram of a system according to one or more embodiments shown and described herein. Figure 1 Artificial muscles along Figure 2A cross-sectional view taken along line 3-3 in FIG.

[0014] Figure 4A schematically depicts a cross-sectional view of another illustrative artificial muscle in a non-actuated state according to one or more embodiments shown and described herein;

[0015] Figure 4B Schematically depicts an actuated state according to one or more embodiments shown and described herein. Figure 4A Cross-sectional view of the artificial muscle;

[0016] Figure 5A schematically depicts a top view of an exemplary artificial muscle stack including a plurality of artificial muscle layers positioned in coaxial alignment according to one or more embodiments shown and described herein;

[0017] Figure 5B Schematically depicts a schematic diagram of a non-actuated state according to one or more embodiments shown and described herein. Figure 5A A side view of the artificial muscle stack along line 5B-5B;

[0018] Figure 5C Schematically depicts an actuated state according to one or more embodiments shown and described herein. Figure 5A A side view of the artificial muscle stack along line 5B-5B;

[0019] Figure 6A schematically depicts a top view of an exemplary artificial muscle stack including a plurality of artificial muscle layers positioned in an alternating offset arrangement according to one or more embodiments shown and described herein;

[0020] Figure 6B Schematically depicts a schematic diagram of a non-actuated state according to one or more embodiments shown and described herein. Figure 6A A side view of the artificial muscle stack along line 6B-6B;

[0021] Figure 6C Schematically depicts an actuated state according to one or more embodiments shown and described herein. Figure 6A A side view of the artificial muscle stack along line 6B-6B;

[0022] Figure 6D Schematically depicts a schematic diagram of a non-actuated state according to one or more embodiments shown and described herein. Figure 6A A side view of the artificial muscle stack along line 6D-6D;

[0023] Figure 6ESchematically depicts a schematic diagram of a non-actuated state according to one or more embodiments shown and described herein. Figure 6A A side view of the artificial muscle stack along line 6D-6D;

[0024] Figure 7 schematically depicts a top view of an exemplary artificial muscle stack including a plurality of artificial muscle layers positioned in an alternating offset arrangement and augmented with peripheral artificial muscles according to one or more embodiments shown and described herein; and

[0025] Figure 8 Schematically depicts a method for operating according to one or more embodiments shown and described herein. Figure 5A-7 An artificial muscle actuation system of an artificial muscle stack. DETAILED DESCRIPTION

[0026] Embodiments described herein relate to an artificial muscle stack comprising a plurality of artificial muscle layers, each having at least one artificial muscle, arranged to maximize the aggregation of individual artificial muscles. Each individual artificial muscle described herein can be actuated to selectively raise and lower an area of ​​the artificial muscle to provide a selective, on-demand inflatable expandable fluid region. In particular, the one or more artificial muscles each include an electrode pair that can be pulled together by applying a voltage, thereby pushing a dielectric fluid into the expandable fluid region, expanding the expandable fluid region, and raising a portion of the artificial muscle on demand. A first electrode and a second electrode each include two or more tab portions and two or more bridging portions, the bridging portions interconnecting adjacent tab portions, and at least one of the first and second electrodes includes a central opening located between the tab portions and surrounding the expandable fluid region. The tab portion and bridging portion design of the electrode pair facilitates a zipper-like actuation motion to increase the force per unit volume that can be achieved by actuating the artificial muscle.

[0027] For some applications, individual artificial muscles do not generate sufficient actuation force to perform certain desired functions. In these applications, it may be useful to arrange the artificial muscle stack into a layered 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. The embodiments described herein relate to an artificial muscle stack comprising a plurality of artificial muscle layers stacked in an alternating offset arrangement such that each 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. This alternating offset arrangement increases the number of artificial muscles that can be arranged in a particular footprint, thereby facilitating an increase in the achievable actuation force of the artificial muscle stack while maintaining a small footprint. Various embodiments of the artificial muscle stack are described in more detail herein. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts.

[0028] Now refer to Figure 1 and 2 , schematically depicting the artificial muscle stacks 201, 301, 301' ( Figure 5A-7 ). The artificial muscle 100 includes a housing 110, an electrode pair 104, a first electrical insulator layer 111, and a second electrical insulator layer 112. The electrode pair includes a first electrode 106 and a second electrode 108. The first electrode and the second electrode are fixed to opposite surfaces of the housing 110. The first electrical insulator layer is fixed to the first electrode 106, and the second electrical insulator layer is fixed to the second electrode 108. In some embodiments, the housing 110 is a one-piece monolithic layer including: 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 can be a pair of independently manufactured 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 .

[0029] While the embodiments described herein primarily refer to a housing 110 comprising a first film layer 122 and a second film layer 124, rather than a one-piece housing, it should be understood that any arrangement is contemplated. In some embodiments, the first film layer 122 and the second film layer 124 comprise substantially 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.

[0030] The first electrode 106 and the second electrode 108 are both located 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 both aluminum-coated polyester, such as In addition, one of the first electrode 106 and the second electrode 108 is a negatively charged electrode, while the other of the first electrode 106 and the second electrode 108 is a positively charged electrode. For the purposes of this discussion, either electrode 106, 108 can be positively charged as long as the other electrode 106, 108 of the artificial muscle 100 is negatively charged.

[0031] The first electrode 106 has a membrane-facing surface 126 and an opposing inner surface 128. The first electrode 106 is positioned against the first membrane layer 122, in particular, against the first inner surface 114 of the first membrane layer 122. In addition, the first electrode 106 includes a first terminal 130 that extends from the first electrode 106 past an edge of the first membrane layer 122 so that the first terminal 130 can be connected to a power source to actuate the first electrode 106. In particular, the terminal is coupled directly or in series to a power source and a controller of the actuation system 400, as shown. Figure 7 4. Similarly, the second electrode 108 has a membrane-facing surface 148 and an opposing inner surface 150. The second electrode 108 is positioned against the second membrane layer 124, and in particular, against the second inner surface 116 of the second membrane layer 124. The second electrode 108 includes a second terminal 152 that extends from the second electrode 108 past an edge of the second membrane layer 124 so that the second terminal 152 can be connected to a power source and controller of the actuation system 400 to actuate the second electrode 108.

[0032] The first electrode 106 includes two or more tab portions 132 and two or more bridge portions 140. Each bridge portion 140 is located between adjacent tab portions 132, thereby interconnecting the adjacent tab portions 132. Each tab portion 132 has a first end 134 that extends radially from the central axis C of the first electrode 106 to an opposite second end 136 of the tab portion 132, wherein the second end 136 defines a portion of the outer periphery 138 of the first electrode 106. Each bridge portion 140 has a first end 142 that extends radially from the central axis C of the first electrode 106 to an opposite second end 144 of the bridge portion 140, wherein the second end 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 that extends radially from the central axis C of the first electrode 106. The tab length L1 is the distance from the first end 134 to the second end 136 of the tab portion 132, and the bridge length L2 is the distance from the first end 142 to the second end 144 of the bridge portion 140. The tab length L1 of each tab portion 132 is greater than the bridge length L2 of each bridge portion 140. In some embodiments, the bridge length L2 is 20% to 50% of the tab length L1, for example, 30% to 40% of the tab length L1.

[0033] In some embodiments, the two or more tab portions 132 are arranged in a pair or more tab portions 132. Each tab portion 132 includes two tab portions 132 arranged diametrically opposite each other. In some embodiments, the first electrode 106 may include only two tab portions 132 located on opposite sides or ends of the first electrode 106. In some embodiments, as Figure 1 and 2 As shown, the first electrode 106 includes four tab portions 132 and four bridge portions 140 that interconnect adjacent tab portions 132. In this embodiment, the four tab portions 132 are arranged as two pairs of tab portions 132 that are diametrically opposed to each other. In addition, as shown, the first terminal 130 extends from the second end portion 136 of one of the tab portions 132 and is formed integrally therewith.

[0034] Like the first electrode 106, the second electrode 108 includes at least one pair of tab portions 154 and two or more bridge portions 162. Each bridge portion 162 is located between adjacent tab portions 154, interconnecting these adjacent tab portions 154. Each tab portion 154 has a first end 156 that extends radially from the central axis C of the second electrode 108 to an opposite second end 158 of the tab portion 154, wherein the second end 158 defines a portion of the outer periphery 160 of the second electrode 108. Because the first electrode 106 and the second electrode 108 are coaxial with each other, the central axis C of the first electrode 106 and the second electrode 108 are the same. Each bridge portion 162 has a first end 164 that extends radially from the central axis C of the second electrode to an opposite second end 166 of the bridge portion 162, which 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 extending radially from the central axis C of the second electrode 108. Tab length L3 is the distance from the first end 156 to the second end 158 of the tab portion 154, and bridge length L4 is the distance from the first end 164 to the second end 166 of the bridge portion 162. Tab length L3 is greater than bridge length L4 of each bridge portion 162. In some embodiments, bridge length L4 is 20% to 50% of tab length L3, for example, 30% to 40% of tab length L3.

[0035] In some embodiments, the two or more tab portions 154 are arranged as a pair or more tab portions 154. Each tab portion 154 includes two tab portions 154 arranged diametrically opposite to each other. In some embodiments, the second electrode 108 may include only two tab portions 154 located on opposite sides or ends of the first electrode 106. Figure 1 and 2 As shown, the second electrode 108 includes four tab portions 154 and four bridge portions 162 that interconnect adjacent tab portions 154. In this embodiment, the four tab portions 154 are arranged as two pairs of tab portions 154 that are diametrically opposed to each other. In addition, as shown, the second terminal 152 extends from the second end portion 158 of one of the tab portions 154 and is formed integrally therewith.

[0036] Now refer to Figure 1-4B At least one of the first electrode 106 and the second electrode 108 has a central opening formed therein, the central opening being located between the first end 134 of the tab portion 132 and the first end 142 of the bridge portion 140. Figure 3A and 3B, the first electrode 106 has a central opening 146. However, it should be understood that when the central opening is provided within the second electrode 108, the first electrode 106 need not include the central opening 146. Figure 4A and 4B Alternatively, when the central opening 146 is provided in the first electrode 106, the second electrode 108 does not need to include a central opening. Still referring to Figure 1-4B , the first and second electrical insulator layers 111, 112 have geometries that generally correspond to the first and second electrodes 106, 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 on the first and second electrodes 106, 108. Furthermore, the first and second electrical insulator layers 111, 112 each have an outer perimeter 178, 180 that, when the first and second electrical insulator layers are positioned over the first and second electrodes, correspond to the outer perimeter 138, 160 of the first and second electrodes 106, 108, respectively.

[0037] It should be understood that in some embodiments, first electrical insulator layer 111 and second electrical insulator layer 112 include substantially the same structure and composition. Thus, in some embodiments, first electrical insulator layer 111 and second electrical insulator layer 112 each include adhesive surfaces 182, 184 and opposing non-sealing surfaces 186, 188, respectively. Thus, in some embodiments, first electrical insulator layer 111 and second electrical insulator layer 112 are each a polymer tape adhered to inner surface 128 of first electrode 106 and inner surface 150 of second electrode 108, respectively.

[0038] Now refer to Figure 2-4B , the artificial muscle 100 is shown in its assembled form, wherein the first terminal 130 of the first electrode 106 and the second terminal 152 of the second electrode 108 extend through the outer periphery of the housing 110 (i.e., the first membrane layer 122 and the second membrane layer 124). Figure 2As shown, the second electrode 108 is stacked on top of the first electrode 106, and therefore the first electrode 106, the first film layer 122, and the second film layer 124 are not shown. In their assembled form, the first electrode 106, the second electrode 108, the first electrical insulator layer 111, and the second electrical insulator layer 112 are sandwiched between the first film layer 122 and the second film layer 124. The first film layer 122 is partially sealed to the second film layer 124 at an area surrounding the outer periphery 138 of the first electrode 106 and the outer periphery 160 of the second electrode 108. In some embodiments, the first film layer 122 is heat sealed to the second film layer 124. In particular, in some embodiments, the first film layer 122 is sealed to the second film layer 124 to define a sealed portion 190 surrounding the first electrode 106 and the second electrode 108. The first film layer 122 and the second film layer 124 can be sealed in any suitable manner, such as using an adhesive, a heat seal, or the like.

[0039] 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 membrane layer 122 from sealing to the second membrane layer 124, thereby forming an unsealed portion 192. The unsealed portion 192 of the housing 110 includes an electrode region 194 in which the electrode pair 104 is disposed and an expandable fluid region 196 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 on each other. Although not shown, the housing 110 can be cut to conform to 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).

[0040] The dielectric fluid 198 is arranged in the unsealed portion 192 and is free to flow between the first electrode 106 and the second electrode 108. " dielectric " fluid used herein is a medium or material that transmits electromotive force when it is not electrically conductive, so it has low electrical conductivity. Some non-limiting examples of dielectric fluids include perfluoroalkanes, transformer oil and deionized water. It should be understood that a needle or other suitable injection devices can be used to inject dielectric fluid 198 into the unsealed portion 192 of the artificial muscle 100.

[0041] Now refer to Figure 3A and 3B , the artificial muscle 100 can be actuated between a non-actuated state and an actuated state. In the non-actuated state, such as Figure 3AAs shown, the first electrode 106 and the second electrode 108 are partially spaced apart from each other near their central openings 146, 168 and the first ends 134, 156 of the tab portions 132, 154. Because the housing 110 is sealed at the outer periphery 138, 160 of the first electrode 106 and the outer periphery 160 of the second electrode 108, the second ends 136, 158 of the tab portions 132, 154 are held in position relative to each other. In the actuated state, as shown Figure 3B As shown, the first and second electrodes 106, 108 are in contact and oriented parallel to each other to force the dielectric fluid 198 into the expandable fluid region 196. This causes the dielectric fluid 198 to flow through the central openings 146, 168 of the first and second electrodes 106, 108 and inflate the expandable fluid region 196.

[0042] Now refer to Figure 3A , the artificial muscle 100 is shown as being in a non-actuated state. The electrode pair 104 is arranged in the electrode area 194 of the 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 in the expandable fluid region 196. In the non-actuated state, the first electrode 106 and the second electrode 108 are partially spaced apart from each other and are not parallel to each other. Because the first membrane layer 122 is sealed to the second membrane layer 124 around the electrode pair 104, the second ends 136, 158 of the tab portions 132, 154 are in contact with each other. Therefore, 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 near 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 causes the electrode pair 104 to zip toward the expandable fluid region 196 when actuated. In some embodiments, the first electrode 106 and the second electrode 108 can be flexible. Thus, as Figure 3A As shown, first and second electrodes 106, 108 are convexly shaped such that second ends 136, 158 of their tab portions 132, 154 can remain proximate to each other but spaced apart near central openings 146, 168. In the unactuated state, expandable fluid region 196 has a first height H1.

[0043] When actuated, Figure 3BAs shown, the first electrode 106 and the second electrode 108 are zippered toward each other from the second ends 144, 158 of their tab portions 132, 154, thereby pushing the dielectric fluid 198 into the expandable fluid region 196. As shown, when 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 to inflate the expandable fluid region 196. Therefore, 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 non-actuated state. Although not shown, it should be noted that the electrode pair 104 can be partially actuated to a position between the non-actuated state and the actuated state. This will allow the partial inflation of the expandable fluid region 196 and allow adjustment when necessary.

[0044] In order to move the first electrode 106 and the second electrode 108 toward each other, a power source (e.g., Figure 7 48 ) applies a voltage. In some embodiments, a voltage of up to 10 kV can be provided from the power supply to induce an electric field through the dielectric fluid 198. The resulting attraction between the first electrode 106 and the second electrode 108 pushes the dielectric fluid 198 into the expandable fluid region 196. The pressure from the dielectric fluid 198 within the expandable fluid region 196 causes the first membrane 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 causes the second membrane 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. Once the voltage supplied to the first electrode 106 and the second electrode 108 is interrupted, the first electrode 106 and the second electrode 108 return to their initial, non-parallel positions in the non-actuated state. In operation, a voltage can be applied to the first electrode 106 and the second electrode 108. Figure 5A-7 One or more artificial muscles 100 of an artificial muscle stack 201 , 301 , 301 ′ can be used to collectively and / or selectively actuate these artificial muscles 100 of the artificial muscle stack 201 , 301 , 301 ′.

[0045] It should be understood that these embodiments of the artificial muscle 100 disclosed herein, and in particular, the tab portions 132, 154 and the interconnected bridging portions 174, 176, together provide many improvements over actuators that do not include the 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" published by E. Acome, SK Mitchell, TG Morrissey, MBEmmett, C. Benjamin, M. King, M. Radakovitz, and C. Keplinger (Science, January 5, 2018: Vol. 359, No. 6371, pp. 61-65). Compared to known HASEL actuators including annular electrodes with uniform radially extending widths, embodiments of artificial muscle 100 including two tab portions 132, 154 on each of first electrode 106 and second electrode 108, respectively, reduce the overall mass and thickness of artificial muscle 100, lower the voltage required during actuation, and reduce the overall volume of artificial muscle 101 without reducing the amount of force generated upon actuation. More specifically, compared to HASEL actuators including annular electrodes, tab portions 132, 154 of artificial muscle 100 provide a zipper-like motion front that results in increased actuation power by providing localized and uniform hydraulic actuation of artificial muscle 100. Specifically, one tab portion 132, 154 provides twice the amount of actuator power per unit volume, while two tab portions 132, 154 provide four times the amount of actuator power per unit volume, compared to annular HASEL actuators. The bridge portions 174, 176 interconnecting the tab portions 132, 154 also limit buckling of the tab portions 132, 154 by maintaining a 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 attachment points that could increase the risk of rupture.

[0046] In operation, when the artificial muscle 100 is actuated, the expansion of the expandable fluid region 196 produces a flow of 100 psi per cubic centimeter (cm 3) actuator volume of 3 Newton-millimeters (N.mm) or greater, such as 4 N.mm per cubic centimeter or greater, 5 N.mm per cubic centimeter or greater, 6 N.mm per cubic centimeter or greater, 7 N.mm per cubic centimeter or greater, 8 N.mm or greater, and so on. In one example, when the artificial muscle 100 is actuated by a voltage of 9.5 kilovolts (kV), the artificial muscle 100 provides a net force of 5 N. In another example, when the artificial muscle 100 is actuated by a voltage of 10 kV, the artificial muscle 100 provides a strain of 440% under a load of 500 grams.

[0047] Furthermore, the size of the first electrode 106 and the second electrode 108 are proportional to the amount of displacement of the dielectric fluid 198. Thus, when a greater displacement is desired within the expandable fluid region 196, 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, alternatively or additionally, the degree of displacement within the expandable fluid region 196 can be controlled by increasing or decreasing the size of the central openings 146, 168.

[0048] like Figure 4A and 4B , another embodiment of an artificial muscle 100' is shown. Artificial muscle 100' is substantially similar to artificial muscle 100. Therefore, similar structures are represented by similar reference numerals. However, as shown, first electrode 106 does not include a central opening. Therefore, only second electrode 108 includes a central opening 168 formed therein. Figure 8 As shown, the artificial muscle 100' is in a non-actuated state, wherein the first electrode 106 is planar and the second electrode 108 is convex relative to the first electrode 106. In the non-actuated state, the expandable fluid region 196 has a first height H3. In the actuated state, as shown Figure 4B As shown, the expandable fluid region 196 has a second height H4 that is greater than the first height H3. It should be understood that by providing the central opening 168 only in the second electrode 108, rather than in both the first electrode 106 and the second electrode 108, the total deformation can be formed on one side of the artificial muscle 100'. In addition, when all other dimensions, directions, and volumes of the dielectric fluid are the same, compared to the second height H2 of the expandable fluid region 196 of the artificial muscle 100, the second height H4 of the expandable fluid region 196 of the artificial muscle 100' extends further from the longitudinal axis perpendicular to the central axis C of the artificial muscle 100' because the total deformation is formed only on one side of the artificial muscle 100'.

[0049] Now refer to Figure 5A-7, depicting artificial muscle stacks 201, 301, 301'. Figure 5A-7 In the embodiment, each artificial muscle stack 201, 301, 301' comprises a plurality of artificial muscle layers 210, 310, and each artificial muscle layer in the plurality of artificial muscle layers 210, 310 comprises one or more artificial muscles 100. In some embodiments, the plurality of artificial muscle layers may alternatively or additionally comprise Figure 4A and 4B In operation, the artificial muscle stack 201 , 301 , 301 ′ generates a greater actuation force than a single artificial muscle 100 . Figure 5A-7 Several different stacking arrangements that can be used to produce increased actuation forces are depicted.

[0050] Figures 5A-5C The artificial muscle stack 201 includes a plurality of artificial muscle layers 210 arranged in a coaxial alignment such that the expandable fluid region 196 of each individual artificial muscle 100 of an individual artificial muscle layer 210 is coaxially aligned with the individual artificial muscles 100 of each of the other individual artificial muscle layers 210. Figure 5B and 5C As shown in the side view of FIG, the artificial muscle stack 201 includes three artificial muscle layers 210A-210C. It should be understood that any number of artificial muscle layers 210 are contemplated. Figure 5B depicts an artificial muscle stack 201 in an unactuated state, Figure 5C An artificial muscle stack 201 is depicted in an actuated state. In each layer of the artificial muscle stack 201, the individual artificial muscles 100 do not overlap. Therefore, although Figures 5A-5B The artificial muscle stack 201 can generate a common actuation force, but the coaxial alignment of the individual artificial muscles 100 of each artificial muscle layer 210 creates a large footprint. In order to reduce the footprint of the artificial muscle arrangement, it is possible to implement Figures 6A-6E Artificial muscle stack 301 is depicted in FIG.

[0051] Figures 6A-6E The artificial muscle stack 301 includes a plurality of artificial muscle layers 310 arranged in an alternating offset arrangement. The artificial muscle stack 301 includes four artificial muscle layers 310, namely 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, Figures 6B-6E is a side view of artificial muscle stack 301. Figure 6B and 6C The artificial muscle stack 301 is shown along line 6B-6B in an unactuated state ( Figure 6B ) and actuation state ( Figure 6C) side view. Figure 6D and 6E The artificial muscle stack 301 is shown along line 6D-6D in an unactuated state ( Figure 6D ) and actuation state ( Figure 6E ). Line 6B-6B is orthogonal to line 6D-6D, so Figure 6B and 6C One side of the artificial muscle stack 301 is shown with Figure 6D and 6E different, Figure 6B and 6C The side shown is perpendicular to Figure 6D and 6E Side shown.

[0052] Each artificial muscle layer 310 includes one or more artificial muscles 100, for example, a plurality of artificial muscles 100. Figure 6A , the first artificial muscle 100A is illustrative of an artificial muscle 100 of an artificial muscle stack 301. It should be understood that embodiments are envisioned in which some of the artificial muscle layers 310 of the artificial muscle stack 301 comprise a single artificial muscle 100. Figures 6A-6E In the depicted alternating offset arrangement of the artificial muscle stack 301, the plurality of 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 with 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 with 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 may overlap with the expandable fluid region 196 of an artificial muscle 100 in an adjacent artificial muscle layer 310 such that the second end portion 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 artificial muscle layer 310. Thus, some of the expandable fluid regions 196 may overlap with two tab portions 132, 154 on one or both sides of the expandable fluid region 196, each tab portion being from a different artificial muscle 100. The tab portion 154 of the second electrode 108 of the electrode pair 104 is located at Figure 6A , but it should be understood that the electrode pair 104 also includes a first electrode 106 having a tab portion 132 .

[0053] Description Figures 6A-6EThe alternating offset arrangement of the artificial muscle stack 301 in FIG. 3 is illustrated using the relative line thickness of the artificial muscle 100 of each artificial muscle layer 310 to illustrate the relative spatial positioning of the corresponding artificial muscle layer 310. For example, in Figure 6A , the first artificial muscle layer 310A is the top layer, so the artificial muscle 100 of the first artificial muscle layer 310A is depicted with the thickest line thickness among the plurality of artificial muscle layers 310. Similarly, in Figure 6A , the fourth artificial muscle layer 310D is the bottom layer, and thus the artificial muscles 100 of the fourth artificial muscle layer 310D are depicted with the thinnest line thickness among the plurality of artificial muscle layers 310 .

[0054] In the alternating offset arrangement of the artificial muscle stack 301, adjacent artificial muscle layers 310 of the artificial muscle stack 301 are offset relative to each other along one or more tab axes (e.g., a first tab axis 10 or a second tab axis 12). Each tab axis extends from the central axis C of the expandable fluid region 196 of an individual artificial muscle 100 of the plurality of artificial muscle layers 310 to an end (i.e., a second end 136, 158) of at least one of the tab portions 132, 154 of the individual artificial muscle 100 in the plurality of artificial muscle layers 310. Figures 6A-6E The embodiments of artificial muscles 100 of the artificial muscle stack 301 depicted in FIG. 1 each include four tab portions 132, 154 arranged in diametrically opposed pairs, with a first tab axis 10 being orthogonal to a second tab axis 12. 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), it should be understood that embodiments are contemplated in which the artificial muscles 100 include more or fewer than four tab portions 132, 154. These embodiments may include more than two tab axes, such as in embodiments with three tab portions per electrode, five tab portions per electrode, or six tab portions per electrode, or may include only a single tab axis, such as in 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 arrangement, such as in triangular or rectangular artificial muscles.

[0055] Still refer to Figures 6A-6E , embodiments of the artificial muscle stack 301 comprising at least three artificial muscle layers 310 include at least one inner artificial muscle layer, which is an artificial muscle layer 310 adjacent to two other artificial muscle layers 310. In these embodiments, each inner artificial muscle layer is offset relative to a first adjacent artificial muscle layer along a first tab axis 10 and relative to a second adjacent artificial muscle layer along a second tab axis 12. This multi-axis offset is Figures 6B-6E The side view of the lateral offset is depicted by a lateral offset showing the offset along one tab axis and a relative line thickness showing the offset along the other tab axis. Figure 6B and 6C In FIG, the offset between the artificial muscle layers 310 along the second splice axis 12 is shown by the lateral offset, and the offset between adjacent artificial muscle layers 310 along the first splice axis 10 is shown by the relative line thickness. In particular, Figure 6B and 6C The thicker line thickness in FIG represents that the artificial muscle layer 310 is offset into the foreground (ie, out of the page) along the first tab axis 10 . Figure 6B and 6C The thinner line thickness in FIG represents the artificial muscle layer 310 moving into the background (ie, into the page) along the first tab axis 10. Figure 6D and 6E In FIG, the offset between the artificial muscle layers 310 along the first splice axis 10 is shown by the lateral offset, and the offset between adjacent artificial muscle layers 310 along the second splice axis 12 is shown by the relative line thickness. In particular, Figure 6D and 6E The thicker line thickness in FIG represents that the artificial muscle layer 310 is offset into the foreground (ie, out of the page) along the second tab axis 12 . Figure 6D and 6E The thicker line weight in FIG. 3 represents the artificial muscle layer 310 being offset into the background (ie, into the page) along the second tab axis 12 .

[0056] exist Figures 6A-6E In the embodiment of the present invention, 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 relative to the first artificial muscle layer 310A along the first tab axis 10 and relative to the third artificial muscle layer 310C along the second tab axis 12. The third artificial muscle layer 310C is offset relative to the second artificial muscle layer 310B along the second tab axis 12 and relative to the fourth artificial muscle layer 310D along the first tab axis 10. This pattern can be repeated in artificial muscle stacks 301 with increasing numbers of artificial muscle layers 310, thereby allowing for a tightly packed stacked arrangement of artificial muscle layers.

[0057] Still refer to Figures 6A-6EIn the alternating offset arrangement of the artificial muscle stack 301, the overlap between the tab portions 132, 154 and the expandable fluid regions 196 in the adjacent artificial muscle layer 310 allows an increased number of artificial muscles 100 to be positioned within a given footprint compared to the artificial muscle stack 201 of Figures 5A-5C. In effect, the artificial muscle stack 301 maximizes the number of artificial muscles 100 that can be positioned within a given footprint in both the lateral direction (i.e., along the first and second tab axes 10, 12) and the depth direction, thereby maximizing the collective actuation force per unit volume of the artificial muscle stack 301. As each artificial muscle 100 actuates, the tab portions 132, 154 of the electrode pair 104 move closer together (e.g., flatten) and the expandable fluid regions 196 expand. Because the tab portions 132, 154 flatten, the expandable fluid regions 196 of the artificial muscle 100 can be positioned above and / or below the tab portions of the adjacent artificial muscle layer 310. This allows a greater number of artificial muscles to be positioned together in a compression block (i.e., artificial muscle stack 301) and to operate in concert. In effect, artificial muscle stack 301 is designed so that the artificial muscles 100 of each artificial muscle layer 310 can exert their collective force in an additive manner. In contrast, Figure 5A The coaxial alignment of the artificial muscle stack 201 limits the cumulative force generated by each artificial muscle layer 210 because the expandable fluid regions 196 of each artificial muscle layer 210 overlap.

[0058] Now refer to Figure 7 , depicting an artificial muscle stack 301 ′. The artificial muscle stack 301 ′ comprises Figures 6A-6E The artificial muscle stack 301 of FIG. 301 is further provided with a peripheral artificial muscle 315. The peripheral artificial muscle 315 includes the same structure as the artificial muscle 100, but has fewer tab portions 132, 154 than the artificial muscle 100 of the artificial muscle stack 301', as shown by the first peripheral artificial muscle 315A. Figure 7 As shown, the artificial muscle 100 of the artificial muscle stack 301′ includes four tab portions 132, 154, and the peripheral artificial muscle 315 includes two or three tab portions 132, 154. In particular, the peripheral artificial muscle 315 may include an edge peripheral artificial muscle 316 and a corner peripheral artificial muscle 318. The edge peripheral artificial muscle 316 extends along a single side of the artificial muscle stack 301, and the corner peripheral artificial muscle 318 is arranged at a corner of the artificial muscle stack 301, such that one tab portion of the corner peripheral artificial muscle 318 extends along one side of the artificial muscle stack 301 and the other tab portion of the corner peripheral artificial muscle 318 extends along the other side of the artificial muscle stack 301.

[0059] like Figures 6A-6EAs shown, the alternating offset arrangement of the plurality of artificial muscle layers 310 of the artificial muscle stack 301 forms a symmetrical imbalance along the edge of the artificial muscle stack 301. That is, due to the alternating offset arrangement, the artificial muscle layers 310 may terminate laterally at different positions, thereby leaving edge gaps in the artificial muscle stack 301. Figure 7 As shown, perimeter artificial muscles 315 can be used to fill these edge gaps, so that each artificial muscle layer 310 of the artificial muscle stack 301' is laterally connected. In some embodiments, each artificial muscle layer 310 can include perimeter artificial muscles 315, for example, a combination of edge perimeter artificial muscles 316 and corner perimeter artificial muscles 318, to balance the symmetry along the edges of the artificial muscle stack 301 while adding additional driving force to the artificial muscle stack 301 without increasing the overall footprint.

[0060] Now refer to Figure 8 , an actuation system 400 may be provided to operate each individual artificial muscle 100 of the artificial muscle stacks 201, 301, 301'. The actuation system 400 may include a controller 50, an operating device 46, a power supply 48, a display device 42, network interface hardware 44, and a communication path 41 for communicatively coupling these components.

[0061] The controller 50 includes a processor 52 and a non-transient electronic memory 54, to which each component is communicatively coupled. In some embodiments, the processor 52 and the non-transient electronic memory 54 and / or other components are contained within a single device. In other embodiments, the processor 52 and the non-transient electronic memory 54 and / or other components may be distributed among multiple communicatively coupled devices. The controller 50 includes a non-transient electronic memory 54 that stores a set of machine-readable instructions. The processor 52 executes the machine-readable instructions stored in the non-transient electronic memory 54. The non-transient electronic memory 54 may include RAM, ROM, flash memory, a hard drive, or any device capable of storing machine-readable instructions so that the machine-readable instructions can be accessed by the processor 52. Therefore, the actuation system 400 described herein can be implemented in any conventional computer programming language, can be implemented as pre-programmed hardware elements, or can be implemented as a combination of hardware and software components. The non-transient electronic memory 54 can be implemented as one memory module or multiple memory modules.

[0062] In some embodiments, non-transitory electronic storage 54 includes instructions for performing the functions of actuation system 400. These instructions may include instructions for operating artificial muscle stacks 201, 301, 301', for example, instructions for actuating one or more artificial muscles 100, independently or collectively, and instructions for actuating artificial muscle layers 210, 310, independently or collectively.

[0063] The processor 52 can be any device capable of executing machine-readable instructions. For example, the processor 52 can be an integrated circuit, a microchip, a computer, or any other computing device. The non-transitory electronic memory 54 and the processor 52 are connected to a communication path 41, which provides signal interconnection between the various components and / or modules of the actuation system 400. Therefore, the communication path 41 can communicatively connect any number of processors to each other and allow the modules connected to the communication path 41 to operate in a distributed computing environment. In particular, each of the modules can operate as a node that can send and / or receive data. As used herein, the term "communicative connection" means that the connected components are able to exchange data signals with each other, for example, electrical signals via a conductive medium, electromagnetic signals via air, optical signals via optical waveguides, and the like.

[0064] like Figure 8 As schematically depicted in FIG, communication path 41 communicatively couples processor 52 and non-transitory electronic memory 54 of controller 50 with various other components of actuation system 400. For example, Figure 8 The actuation system 400 depicted in FIG. 4 includes a processor 52 and a non-transitory electronic memory 54 , both of which are communicatively coupled with an operating device 46 and a power source 48 .

[0065] The operating device 46 allows a user to control the operation of the artificial muscles 100 of the artificial muscle stacks 201, 301, 301'. In some embodiments, the operating device 46 can be any combination of switches, toggle switches, buttons, or controls to provide user operation. The operating device 46 is coupled to the communication path 41 so that the communication path 41 communicatively couples the operating device 46 to the other modules of the actuation system 400. The operating device 46 can provide a user interface for receiving user instructions regarding a specific operational configuration of the artificial muscle stacks 201, 301, 301'.

[0066] 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 to provide power to the one or more artificial muscles 100 of the artificial muscle stacks 201, 301, 301' via the power source 48.

[0067] In some embodiments, the actuation system 400 further 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 the other modules of the actuation system 400. The display device 42 may be a touch screen that, in addition to providing optical information, detects the presence and location of tactile input on or near the surface of the display device 42. Thus, the display device 42 may include an operating device 46 and receive mechanical input directly on the optical output provided by the display device 42.

[0068] 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 computer, a personal media player, or any other electronic device that includes wireless communication capabilities. It should be understood that, when provided, the portable device 70 may be used to provide user commands to the controller 50 instead of the operating device 46. Thus, the user may be able to control or set a program for controlling the artificial muscles 100 of the artificial muscle stacks 201, 301, 301' using the controller 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.

[0069] It should now be understood that the embodiments described herein relate to an artificial muscle stack comprising a plurality of 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 particular footprint, thereby forming an artificial muscle stack with a small footprint that is capable of achieving a high actuation force per unit volume of the artificial muscle stack.

[0070] It is noted that the terms "substantially" and "about" may be used herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

[0071] While specific embodiments have been illustrated and described herein, it will be appreciated that various other changes and modifications may be made without departing from the scope of the claimed subject matter. Furthermore, while various aspects of the claimed subject matter have been described herein, these aspects need not be used in combination. Accordingly, the appended claims are intended to cover all such changes and modifications that fall within the scope of the claimed subject matter.

Claims

1. An artificial muscle stack comprising: A plurality of artificial muscle layers, wherein each artificial muscle layer comprises at least one artificial muscle, wherein the at least one artificial muscle comprises: a housing comprising an electrode region and an expandable fluid region; a dielectric fluid contained within the housing; and an electrode pair comprising a first electrode and a second electrode located in an electrode region of the housing, wherein: 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 bridging portions interconnects adjacent tab portions; and At least one of the first electrode and the second electrode includes a central opening between the two or more tab portions and surrounding the expandable fluid region; and The plurality of artificial muscle layers are arranged such that the expandable fluid region of the at least one artificial muscle of each artificial muscle layer overlaps with at least one tab portion of at least one artificial muscle of an adjacent artificial muscle layer.

2. The artificial muscle stack according to claim 1, wherein: Adjacent artificial muscle layers are offset from each other along one or more splice axes, each splice axis extending from a central axis of an expandable fluid region of an independent artificial muscle of the multiple artificial muscle layers to an end of at least one of two or more splice portions of the independent artificial muscle of the multiple artificial muscle layers.

3. The artificial muscle stack according to claim 2, wherein: The plurality of artificial muscle layers includes at least three artificial muscle layers, and each inner artificial muscle layer is offset relative to a first adjacent artificial muscle layer along a first tab axis and relative to a second adjacent artificial muscle layer along a second tab axis.

4. The artificial muscle stack according to claim 3, wherein: The first web axis is orthogonal to the second web axis.

5. The artificial muscle stack according to claim 1, wherein: At least one of the plurality of artificial muscle layers further comprises one or more peripheral artificial muscles; as well as The one or more peripheral artificial muscles include fewer tab portions than other artificial muscles of the at least one artificial muscle layer in the plurality of artificial muscle layers.

6. The artificial muscle stack according to claim 1, wherein: Each of the plurality of artificial muscle layers includes a plurality of artificial muscles.

7. The artificial muscle stack according to 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 interconnecting an adjacent pair of adjacent tab portions, each tab portion being diametrically opposed to an opposing tab portion.

8. The artificial muscle stack according to 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. The artificial muscle stack according to claim 1, wherein: The electrode pair is actuatable between a non-actuated state and an actuated state, such that actuation from the non-actuated state to the actuated state directs a dielectric fluid into the expandable fluid region, thereby expanding the expandable fluid region.

10. The artificial muscle stack of claim 9, wherein: When the electrode pair is in the non-actuated state, the first electrode and the second electrode are not parallel to each other; as well as 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 move toward each other and toward the center opening zipper when actuated from the non-actuated state to the actuated state.

11. The artificial muscle stack according to claim 1, wherein: The artificial muscle stack also includes a first electrical insulator layer and a second electrical insulator layer, wherein the first electrical insulator layer is fixed to the inner surface of the first electrode opposite to the first surface of the shell, and the second electrical insulator layer is fixed to the inner surface of the second electrode opposite to the second surface of the shell, wherein the first electrical insulator layer and the second electrical insulator layer each include an adhesive surface and an opposite non-sealable surface.

12. An artificial muscle stack comprising: Three or more artificial muscle layers, wherein each artificial muscle layer comprises at least one artificial muscle, the at least one artificial muscle comprising: a housing comprising an electrode region and an expandable fluid region; a dielectric fluid contained within the housing; and an electrode pair comprising a first electrode and a second electrode located in an electrode region of the housing, wherein: 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 bridging portions interconnects adjacent tab portions; and At least one of the first electrode and the second electrode includes a central opening between the two or more tab portions and surrounding the expandable fluid region; and in: Each interiorly located artificial muscle layer is offset along a first tab axis relative to a first adjacent artificial muscle layer and offset along a second tab axis relative to a second adjacent artificial muscle layer; and Each tab axis extends from the central axis of the expandable fluid region to an end of at least one of the two or more tab portions of the at least one artificial muscle of each interior artificial muscle layer.

13. The artificial muscle stack according to claim 12, wherein: The first web axis is orthogonal to the second web axis.

14. The artificial muscle stack according to claim 12, wherein: The electrode pair is actuatable between a non-actuated state and an actuated state, such that actuation from the non-actuated state to the actuated state directs a dielectric fluid into the expandable fluid region, thereby expanding the expandable fluid region.

15. The artificial muscle stack according to 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. The artificial muscle stack according to claim 12, wherein: Each of the three or more artificial muscle layers includes a plurality of artificial muscles.

17. A method for actuating an artificial muscle stack, the method comprising: A voltage is generated using a power supply electrically coupled to the electrode pairs of each artificial muscle of the plurality of artificial muscle layers, wherein: 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 comprises a first electrode and a second electrode and is located in the electrode region of the housing, wherein: 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 bridging portions interconnects adjacent tab portions; and at least one of the first electrode and the second electrode comprises a central opening between the two or more tab portions and surrounding the expandable fluid region, wherein 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; and The voltage is applied to an electrode pair of at least one artificial muscle of at least one artificial muscle layer among the plurality of artificial muscle layers, thereby actuating the electrode pair of the at least one artificial muscle from a non-actuated state to an actuated state, so that a dielectric fluid is introduced into the expandable fluid region of the shell and expands the expandable fluid region.

18. The method according to claim 17, wherein Adjacent artificial muscle layers are offset from each other along one or more splice axes, each splice axis extending from a central axis of an expandable fluid region of an independent artificial muscle of the multiple artificial muscle layers to an end of at least one of two or more splice portions of the independent artificial muscle of the multiple artificial muscle layers.

19. The method according to claim 18, wherein The plurality of artificial muscle layers includes at least three artificial muscle layers, each inner artificial muscle layer being offset relative to a first adjacent artificial muscle layer along a first tab axis and relative to a second adjacent artificial muscle layer along a second tab axis.

20. The method according to claim 17, wherein The method also includes applying a voltage to the electrode pairs of each artificial muscle of each artificial muscle of each artificial muscle layer in the plurality of artificial muscle layers, thereby actuating the electrode pairs of each artificial muscle from the non-actuated state to the actuated state, causing the dielectric fluid to be directed into the expandable fluid region of the housing of each artificial muscle, thereby expanding the expandable fluid region of each artificial muscle.

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