Artificial muscle with gradient stiffened electrode pair and artificial muscle assembly including the same

Abstract

To provide artificial muscles comprising an electrode pair, and a method for actuating the artificial muscles.SOLUTION: Artificial muscles are provided including: a housing having an electrode region and an expandable fluid region; an electrode pair comprising a first electrode and a second electrode that are positioned in the electrode region of the housing; a dielectric fluid housed in the housing; and a stiffening member positioned between the housing and at least one of the first electrode and the second electrode. The stiffening member increases a stiffness of the housing in a direction toward the expandable fluid region from an opposite edge of the electrode region. The electrode pair is actuatable between a non-actuated state and an actuated state such that the actuation from the non-actuated state to the actuated state directs the dielectric fluid into the expandable fluid region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present specification relates generally to an apparatus and method for focused expansion on at least one surface of a device, and more particularly to an apparatus and method for directing a fluid to expand a device utilizing an electrode pair. [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. HASEL actuator artificial muscles include a housing with uniform stiffness that compresses when actuated to push fluid into an expandable fluid region. However, the housing may compress to direct fluid away from the expandable fluid region due to the housing's uniform stiffness.

[0004] Therefore, there is a need for improved artificial muscles with gradient stiffness so that they can be actuated to more effectively direct fluid into expandable fluid regions. Summary of the Invention

[0005] In one embodiment, an artificial muscle includes a housing having an electrode region and an expandable fluid region; an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; a dielectric fluid contained within the housing; and a stiffening member positioned between the housing and at least one of the first electrode and the second electrode, the stiffening member increasing the stiffness of the housing in a direction from an opposite edge of the electrode region toward the expandable fluid region, the electrode pair being 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.

[0006] In another embodiment, an artificial muscle includes a housing having an electrode region and an expandable fluid region; an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; a dielectric fluid contained within the housing; and a pair of stiffening members positioned between the housing and each of the first electrode and the second electrode, the pair of stiffening members increasing the stiffness of the housing in a direction from the side ends of the electrode region toward the expandable fluid region, the electrode pairs actuable between an unactuated state and an actuated state such that actuation from the unactuated state to the actuated state decreases the distance between the electrode pairs proximate the side ends of the electrode region before the distance between the electrode pairs proximate the expandable fluid region is decreased.

[0007] In yet another embodiment, a method for actuating an artificial muscle includes providing a voltage using a power source electrically coupled to an electrode pair of the artificial muscle, the artificial muscle including a housing having an electrode region and an expandable fluid region, an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing, a dielectric fluid contained within the housing, and a stiffening member positioned between the housing and at least one of the first electrode and the second electrode, the stiffening member increasing the stiffness of the housing in a direction from a side end of the electrode region toward the expandable fluid region; and actuating the electrodes 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.

[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 plan view that schematically depicts the artificial muscle of FIG. 1 according to one or more embodiments shown and described herein. [Figure 3] 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 unactuated state, according to one or more embodiments shown and described herein. [Figure 4] FIG. 2 is a cross-sectional view that schematically depicts the artificial muscle of FIG. 1 in an actuated state, according to one or more embodiments shown and described herein. [Figure 5] FIG. 1 is an exploded view that schematically depicts an exemplary artificial muscle, according to one or more embodiments shown and described herein. [Figure 6] FIG. 6 is a plan view that schematically depicts the artificial muscle of FIG. 5 according to one or more embodiments shown and described herein. [Figure 7] FIG. 7 is a cross-sectional view that schematically depicts the artificial muscle of FIG. 5 taken along line 7-7 of FIG. 6 in an unactuated state, according to one or more embodiments shown and described herein. [Figure 8] FIG. 6 is a cross-sectional view that schematically depicts the artificial muscle of FIG. 5 in an actuated state, according to one or more embodiments shown and described herein. [Figure 9] FIG. 1 is a diagram that schematically depicts an actuation system for operating an artificial muscle according to one or more embodiments shown and described herein. DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiments described herein are directed to artificial muscles and methods of operating artificial muscles. The artificial muscles described herein are actuatable to selectively raise and lower regions of the artificial muscle to provide selective, on-demand expanded, expandable fluid regions. The artificial muscle includes a housing and an electrode pair. A dielectric fluid is contained within the housing, the housing including an electrode region and an expandable fluid region, and the electrode pair is positioned in the electrode region. The electrode pair includes a first electrode and a second electrode positioned in the electrode region of the housing. A stiffening member is positioned between the housing and at least one of the first electrode and the second electrode. The stiffening member increases the stiffness of the housing in a direction from a side end of the electrode region toward the expandable fluid region. The housing having an increasing stiffness extending in a direction toward the expandable fluid region results in the end of the housing opposite the expandable fluid region being compressed first when the electrode pair is actuated and zipping toward the expandable fluid region. The electrode pairs are actuable between unactuated and actuated states such that actuation from the unactuated state to the actuated state directs dielectric fluid into the expandable fluid region. This expands the expandable fluid region and raises a portion of the artificial muscle on demand. Various embodiments of artificial muscles and their operation 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.

[0012] 1-4, an artificial muscle 100 is shown. As shown in FIG. 1, the artificial muscle 100 includes a housing 102, an electrode pair 104 including a first electrode 106 and a second electrode 108, a first electrical insulator layer 110 secured to the first electrode 106, and a second electrical insulator layer 112 secured to the second electrode 108. The artificial muscle 100 also includes one or more stiffening members positioned between the housing 102 and at least one of the first electrode 106 and the second electrode 108. As shown, a first stiffening member 113 and a second stiffening member 115 are positioned between the housing 102 and the first electrode 106, and a third stiffening member 117 and a fourth stiffening member 119 are positioned between the housing 102 and the second electrode 108.

[0013] In some embodiments, the housing 102 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 102 are heat-sealable. In other embodiments, the housing 102 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 the first inner surface 114 and the first outer surface 118, and the second film layer 124 includes the second inner surface 116 and the second outer surface 120.

[0014] Throughout the following description, reference may be made to the housing 102 including a first film layer 122 and a second film layer 124, as opposed to a one-piece housing. However, it should be understood that 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 an elastomeric material. In some embodiments, the first film layer 122 and the second film layer 124 each comprise biaxially oriented polypropylene. In embodiments, the first film layer 122 and the second film layer 124 each have a total thickness of 1 mil to 5 mils, such as 1.5 mils, 2 mils, 2.5 mils, 3 mils, 3.5 mils, 4 mils, 4.5 mils, or any range having any two of these values ​​as endpoints. Although not shown, each of the first and second film layers 122, 124 may comprise a pair of biaxially oriented polypropylene layers. In one example embodiment, each biaxially oriented polypropylene layer may have a thickness of 1.5 mils to provide a total thickness of 3 mils for each of the first and second film layers 122, 124.

[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, an opposing inner surface 128, a first end 121, and an opposing second end 123. The first electrode 106 has a length L1 extending between the first end 121 and the second end 123. Additionally, the first electrode 106 includes a first terminal 130 that extends from the first end 121 of the first electrode 106 past the 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 130 is coupled, directly or in series, to a power source and controller of the actuation system 300, as shown in FIG. 9 . Similarly, the second electrode 108 has a film-facing surface 148, an opposing inner surface 150, a first end 125, and an opposing second end 127. The second electrode 108 has a length L2 extending between the first end 125 and the second end 127. The second electrode 108 includes a second terminal 152 that extends from the first end 125 of 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 300 to actuate the second electrode 108.

[0017] As noted above, the first stiffening member 113 and the second stiffening member 115 are positioned between the first film layer 122 and the first electrode 106. As discussed in further detail herein, the first stiffening member 113 and the second stiffening member 115 provide a gradient stiffness to gradually or incrementally increase the stiffness of the first film layer 122, which results in a zipping movement of the first film layer 122 in a direction from the first end 121 of the first electrode 106 to the second end 123 of the first electrode 106 when the electrode pair 104 is actuated. Specifically, the first stiffening member 113 has a first end 129 and an opposite second end 131, defining a length L3 therebetween. Additionally, the second stiffening member 115 has a first end 133 and an opposite second end 135, defining a length L4 therebetween. It should be understood that the length L1 of the first electrode 106 is greater than the length L3 of the first stiffener member 113. Additionally, the length L4 of the second stiffener member 115 is between the length L1 of the first electrode 106 and the length L3 of the first stiffener member 113. As shown, the first stiffener member 113 is positioned between the first film layer 122 and the second stiffener member 115, and the second stiffener member 115 is positioned between the first stiffener member 113 and the first electrode 106. Furthermore, the second end 131 of the first stiffener member 113 and the second end 135 of the second stiffener member 115 are aligned with the second end 123 of the first electrode 106 when assembled.

[0018] With respect to the third stiffener member 117 and the fourth stiffener member 119, the third stiffener member 117 has a first end 137 and an opposite second end 139, defining a length L5 therebetween. Additionally, the fourth stiffener member 119 has a first end 141 and an opposite second end 143, defining a length L6 therebetween. It should be understood that the length L2 of the second electrode 108 is greater than the length L5 of the third stiffener member 117. Additionally, the length L6 of the fourth stiffener member 119 is between the length L2 of the second electrode 108 and the length L5 of the third stiffener member 117. As discussed in further detail herein, the third stiffener member 117 and the fourth stiffener member 119 provide a gradient stiffness to gradually or incrementally increase the stiffness of the second film layer 124, which results in a zipping movement of the second film layer 124 in a direction from the first end 125 of the second electrode 108 to the second end 127 of the second electrode 108 when the electrode pair 104 is actuated. As shown, the third stiffener member 117 is positioned between the second film layer 124 and the fourth stiffener member 119, and the fourth stiffener member 119 is positioned between the third stiffener member 117 and the second electrode 108. Furthermore, the second end 139 of the third stiffener member 117 and the second end 143 of the fourth stiffener member 119 are aligned with the second end 127 of the second electrode 108 when assembled.

[0019] In a preferred embodiment, stiffening members 113, 115, 117, and 119 are each biaxially oriented polypropylene layers having a thickness of 1 mil to 2 mils, such as 1 mil, 1.5 mil, or 2 mils, or any range of thicknesses between any two of these values. In embodiments, only one of first stiffening member 113 and second stiffening member 115 is provided between first film layer 122 and first electrode 106. Furthermore, in embodiments, first stiffening member 113 and second stiffening member 115 may be a one-piece monolithic member, such that the thickness of the monolithic member at their first end is less than the thickness of the monolithic member at their opposite second end. The thickness may increase gradually or incrementally in the length direction from the first end to the second end, such as toward second end 123 of first electrode 106. Similarly, in embodiments, only one of the third stiffening member 117 and the fourth stiffening member 119 is provided between the second film layer 124 and the second electrode 108. Furthermore, in embodiments, the third stiffening member 117 and the fourth stiffening member 119 may be one-piece monolithic members such that the thickness of the monolithic member at their first ends is less than the thickness of the monolithic member at their opposite second ends. The thickness may increase gradually or incrementally in the length direction from the first end to the second end, such as toward the second end 127 of the second electrode 108.

[0020] 1 , the first electrical insulator layer 110 includes a first end 145 and an opposite second end 147. Similarly, the second electrical insulator layer 112 has a first end 149 and an opposite second end 151. The first end 145 of the first electrical insulator layer 110 and the first end 149 of the second electrical insulator layer 112 are aligned with the first end 121 of the first electrode 106 and the first end 125 of the second electrode 108, respectively, when assembled. It should be understood that in some embodiments, the first electrical insulator layer 110 and the second electrical insulator layer 112 generally comprise the same structure and composition. As such, in some embodiments, the first electrical insulator layer 110 and the second electrical insulator layer 112 each include adhesive surfaces 182, 184 and opposite non-sealable surfaces 186, 188, respectively. In some embodiments, the first electrical insulator layer 110 and the second electrical insulator layer 112 are each polymeric tapes adhered to the inner surface 128 of the first electrode 106 and the inner surface 150 of the second electrode 108, respectively.

[0021] 2, a top view of artificial muscle 100 is shown in assembled form 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 102. As shown, second electrode 108 is laminated on top of first electrode 106; therefore, only second film layer 124, third stiffening member 117, fourth stiffening member 119, and second electrode 108 are illustrated, as other components are hidden in this view.

[0022] 3 , in the assembled configuration, the first electrode 106, the second electrode 108, the first electrical insulator layer 110, and the second electrical insulator layer 112 are sandwiched between a first film layer 122 and a second film layer 124. Additionally, a first stiffening member 113 and a second stiffening member 115 are positioned between the first film layer 122 and the first electrode 106, and a third stiffening member 117 and a fourth stiffening member 119 are positioned between the second film layer 124 and the second electrode 108. The first film layer 122 is partially sealed to the second film layer 124 in an area surrounding the first electrical insulator layer 110 and the second electrical insulator layer 112. Specifically, the first film layer 122 is sealed to the second film layer 124 to define a seal portion 190 that surrounds the first electrical insulator layer 110 and the second electrical insulator layer 112. In some embodiments, the first film layer 122 is heat sealed to the second film layer 124. However, the first film layer 122 and the second film layer 124 may be sealed in any suitable manner, such as using an adhesive or the like.

[0023] First electrical insulator layer 110 and second electrical insulator layer 112 provide a barrier that prevents a portion of first film layer 122 from sealing to an opposing portion of second film layer 124, thereby forming non-sealed portion 192. Non-sealed portion 192 of housing 102 includes electrode region 194, where electrode pairs 104 are provided, and expandable fluid region 196 adjacent electrode region 194. Although not shown, housing 102 can be cut to fit the geometric shape of first electrical insulator layer 110 and second electrical insulator layer 112 and to reduce the size of artificial muscle 100, i.e., the size of sealed portion 190.

[0024] 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.

[0025] 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 proximal to the second end 123 of the first electrode 106 and the second end 127 of the second electrode 108, as shown in FIG. 3 . The first end 121 of the first electrode 106 and the first end 125 of the second electrode 108 remain in place relative to each other due to the sealed housing 102. 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, as shown in FIG. 4 , forcing the dielectric fluid 198 into the expandable fluid region 196. This causes the dielectric fluid 198 to flow into the expandable fluid region 196, causing it to expand. Specifically, it should be appreciated that the first stiffening member 113 and the second stiffening member 115 cause the first film layer 122 to be progressively more stiff within the electrode region 194 in a direction toward the expandable fluid region 196. Similarly, the third stiffening member 117 and the fourth stiffening member 119 cause the second film layer 124 to be progressively more stiff within the electrode region 194 in a direction toward the expandable fluid region 196. As such, during actuation of the electrode pair 104, the least stiff portions of the first film layer 122 and the second film layer 124, i.e., the portions without any stiffening members 113, 115, 117, 119, are initially drawn toward each other by the actuation of the electrode pair 104. Subsequently, adjacent portions of the first and second film layers 122, 124 that are stiffer than the least stiff portions, i.e., portions that include only the second stiffening member 115 or the fourth stiffening member 119 between them, are attracted toward each other. Then, the remaining portions of the first and second film layers 122, 124 that are stiffest, i.e., portions that include each of the stiffening members 113, 115, 117, 119 between them, are attracted toward each other, as shown in FIG.It should be understood that increasing the stiffness of the first film layer 122 and the second film layer 124 in the direction toward the expandable fluid region 196 encourages the electrodes to "zip" from the first end 121 of the first electrode 106 and the first end 125 of the second electrode 108 toward the second end 123 of the first electrode 106 and the second end 127 of the second electrode 108.

[0026] Referring again to FIG. 3 , the artificial muscle 100 is shown in an unactuated state. The electrode pair 104 is provided within an electrode region 194 of the unsealed portion 192 of the housing 102. In the unactuated state, the first electrode 106 and the second electrode 108 are partially spaced apart and non-parallel to each other. Due to the first film layer 122 being sealed to the second film layer 124, the first end 121 of the first electrode 106 and the first end 125 of the second electrode 108 are in contact with each other. Thus, a dielectric fluid 198 is provided between the first electrode 106 and the second electrode 108, thereby separating the second end 123 of the first electrode 106 and the second end 127 of the second electrode 108 proximal to the expandable fluid region 196. Stated another way, the distance between the second end 123 of the first electrode 106 and the second end 156 of the second electrode 108 is greater than the distance between the first end 121 of the first electrode 106 and the first end 125 of the second electrode 108. In some embodiments, the first electrode 106 and the second electrode 108 may be flexible. In the unactuated state, the expandable fluid region 196 has a height H1.

[0027] When actuated, as shown in FIG. 4 , the first electrode 106 and the second electrode 108 zip toward each other from the first end 121 of the first electrode 106 and the first end 125 of the second electrode 108, as discussed above, 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 height H2, which is greater than the height H1 of the expandable fluid region 196 when in the unactuated state. Note that, although not shown, electrode pair 104 can be partially actuated to a position between the unactuated and actuated states, allowing for partial expansion and adjustment of expandable fluid region 196 as needed.

[0028] A voltage is applied by a power source 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 by 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 deforms the first film layer 122 and the first electrical insulator layer 110 and deforms the second film layer 124 and the second electrical insulator layer 112 in an opposite second axial direction. When the voltage applied 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.

[0029] 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 difference in the lengths of the first and second electrical insulator layers 110 and 112 compared to the length L1 of the first electrode 106 and the length L2 of the second electrode 108. Thus, the degree of displacement within the expandable fluid region 196 is alternatively or additionally controlled by increasing or decreasing the length of the first and second electrical insulator layers 110 and 112.

[0030] 5-8, an artificial muscle 200 is shown. As shown in FIG. 5, artificial muscle 200 is substantially similar to artificial muscle 100 discussed herein, except that the individual layers have a generally plus sign-shaped geometry. As such, artificial muscle 200 includes a housing 202, an electrode pair 204 including a first electrode 206 and a second electrode 208, a first electrical insulator layer 210 secured to first electrode 206, and a second electrical insulator layer 212 secured to second electrode 208. Artificial muscle 200 also includes one or more stiffening members positioned between housing 202 and at least one of first electrode 206 and second electrode 208. As shown, first stiffening member 213 and second stiffening member 215 are positioned between housing 202 and first electrode 206, and third stiffening member 217 and fourth stiffening member 219 are positioned between housing 202 and second electrode 208.

[0031] In some embodiments, housing 202 is a one-piece, monolithic layer including a pair of opposing inner surfaces, such as first inner surface 214 and second inner surface 216, and a pair of opposing outer surfaces, such as first outer surface 218 and second outer surface 220. In some embodiments, first inner surface 214 and second inner surface 216 of housing 202 are heat-sealable. In other embodiments, housing 202 may be a pair of individually fabricated film layers, such as first film layer 222 and second film layer 224. Thus, first film layer 222 includes first inner surface 214 and first outer surface 218, and second film layer 224 includes second inner surface 216 and second outer surface 220.

[0032] Throughout the following description, reference may be made to the housing 202 including a first film layer 222 and a second film layer 224, as opposed to a one-piece housing. It should be understood that either arrangement is contemplated. In some embodiments, the first film layer 222 and the second film layer 224 generally comprise the same structure and composition. For example, in some embodiments, the first film layer 222 and the second film layer 224 each comprise biaxially oriented polypropylene. In embodiments, the first film layer 222 and the second film layer 232 each have a total thickness of 3 mils. Although not shown, the first film layer 222 and the second film layer 232 may each comprise a pair of biaxially oriented polypropylene layers. In embodiments, each biaxially oriented polypropylene layer has a thickness between 1 mil and 2 mils, such as 1 mil, 1.5 mils, 2 mils, or any range of thicknesses between any two of these values. In an embodiment, each biaxially oriented polypropylene layer has a thickness of 1.5 mils, to provide a total thickness of 3 mils for each of the first and second film layers 222, 232.

[0033] First electrode 206 and second electrode 208 are each positioned between first film layer 222 and second film layer 224. In some embodiments, first electrode 206 and second electrode 208 are each an aluminum-coated polyester, such as Mylar®. Additionally, one of first electrode 206 and second electrode 208 is a negatively charged electrode, and the other of first electrode 206 and second electrode 208 is a positively charged electrode. For purposes discussed herein, either electrode 206, 208 can be positively charged as long as the other electrode 206, 208 of artificial muscle 200 is negatively charged.

[0034] The first electrode 206 has a film-facing surface 226 and an opposite inner surface 228. Additionally, the first electrode 206 includes a first terminal 230 that extends from the first electrode 206 past the edge of the first film layer 222 such that the first terminal 230 can be connected to a power source to activate the first electrode 206. Specifically, the terminal is coupled, either directly or in series, to a power source and controller of the actuation system 300, as shown in FIG. 9. Similarly, the second electrode 208 has a film-facing surface 248 and an opposite inner surface 250. The second electrode 208 includes a second terminal 252 that extends from the second electrode 208 past the edge of the second film layer 224 so that the second terminal 130 can be connected to a power source and controller of the actuation system 300 to actuate the second electrode 208.

[0035] The first electrode 206 includes two or more tab portions 232 and two or more bridge portions 240. Each bridge portion 240 is positioned between and interconnects adjacent tab portions 232. Each tab portion 232 has a first end 234 extending radially from a central axis C of the first electrode 206 to an opposing second end 236 of the tab portion 232, which defines a portion of an outer periphery 238 of the first electrode 206. Each bridge portion 240 has a first end 242 extending from the central axis C of the first electrode 206 to an opposing second end 244 of the bridge portion 240, which defines another portion of the outer periphery 238 of the first electrode 206. Each tab portion 232 has a tab length A1, and each bridge portion 240 has a bridge length A2 extending radially from the central axis C of the first electrode 206. Tab length A1 defines the distance from first end 234 to second end 236 of tab portion 232, and bridge length A2 defines the distance from first end 242 to second end 244 of bridge portion 240. Tab length A1 of each tab portion 232 is longer than bridge length A2 of each bridge portion 240. In some embodiments, bridge length A2 is between 20% and 50% of tab length A1, such as between 30% and 40% of tab length A1.

[0036] In some embodiments, the two or more tab portions 232 are arranged in one or more pairs of tab portions 232. Each pair of tab portions 232 includes two tab portions 232 disposed radially opposite one another. In some embodiments, the first electrode 206 may include only two tab portions 232 positioned on opposite sides or both ends of the first electrode 206. In some embodiments, as shown in FIG. 5 , the first electrode 206 includes four tab portions 232 and four bridge portions 240 interconnecting adjacent tab portions 232. In this embodiment, the four tab portions 232 are arranged such that two pairs of tab portions 232 are radially opposed to one another. Additionally, as shown, the first terminal 230 extends from and is integrally formed with the second end 236 of one of the tab portions 232.

[0037] Like the first electrode 206, the second electrode 208 includes at least a pair of tab portions 254 and two or more bridge portions 262. Each bridge portion 262 is positioned between and interconnects adjacent tab portions 254. Each tab portion 254 has a first end 256 that extends radially from a central axis C of the second electrode 208 to an opposing second end 258 of the tab portion 254, which defines a portion of an outer periphery 260 of the second electrode 208. Due to the first electrode 206 and the second electrode 108 being coaxial with each other, the central axis C of the first electrode 106 and the central axis C of the second electrode 108 are the same. Each bridge portion 262 has a first end 264 that extends from the central axis C of the second electrode 208 to an opposing second end 266 of the bridge portion 262 that defines another portion of the outer periphery 260 of the second electrode 208. Each tab portion 254 has a tab length A3, and each bridge portion 262 has a bridge length A4 that extends radially from the central axis C of the second electrode 208. The tab length A3 defines the distance from the first end 256 to the second end 258 of the tab portion 254, and the bridge length A4 defines the distance from the first end 264 to the second end 266 of the bridge portion 262. The tab length A3 is longer than the bridge length A4 of each bridge portion 262. In some embodiments, the bridge length A4 is between 20% and 50% of the tab length A3, such as between 30% and 40% of the tab length A3.

[0038] In some embodiments, the two or more tab portions 254 are arranged in one or more pairs of tab portions 254. Each pair of tab portions 254 includes two tab portions 254 positioned radially opposite one another. In some embodiments, the second electrode 208 may include only two tab portions 254 positioned on opposite sides or opposite ends of the first electrode 206. In some embodiments, as shown in FIG. 5 , the second electrode 208 includes four tab portions 254 and four bridge portions 262 interconnecting adjacent tab portions 254. In this embodiment, the four tab portions 254 are arranged such that two pairs of tab portions 254 are radially opposed to one another. Furthermore, as shown, the second terminal 252 extends from and is integrally formed with the second end 258 of one of the tab portions 254.

[0039] 5 , at least one of the first electrode 206 and the second electrode 208 has a central opening formed between the first end 234 of the tab portion 232 and the first end 242 of the bridge portion 240. As shown, the first electrode 206 has a central opening 246. However, it should be understood that the first electrode 206 need not include the central opening 246 when the central opening 268 is provided in the second electrode 208. Alternatively, the second electrode 208 need not include the central opening 268 when the central opening 246 is provided in the first electrode 206.

[0040] As noted above, the first stiffening member 213 and the second stiffening member 215 are positioned between the first film layer 222 and the first electrode 206. As discussed in more detail herein, the first stiffening member 213 and the second stiffening member 215 provide a gradient stiffness to gradually or incrementally increase the stiffness of the first film layer 222. As shown, the first stiffening member 213 is positioned between the first film layer 222 and the second stiffening member 215, and the second stiffening member 215 is positioned between the first stiffening member 213 and the first electrode 206.

[0041] The first stiffener member 213 and the second stiffener member 215 each have a geometric shape that generally corresponds to the first electrode 206. As such, the first stiffener member 213 includes a tab portion 221 and a bridge portion 223 that extends between adjacent tab portions 221 and defines an outer perimeter 225. Similarly, the second stiffener member 215 includes a tab portion 227 and a bridge portion 229 that extends between adjacent tab portions 227 and defines an outer perimeter 231. However, the first stiffener member 213 and the second stiffener member 215 are dimensionally smaller than the first electrode 206. Specifically, the second stiffener member 215 is dimensionally smaller than the first electrode 206, and the first stiffener member 213 is dimensionally smaller than the second stiffener member 215. In embodiments in which the first electrode 206 has a central opening 246, the first stiffening member 213 has a central opening 233 and the second stiffening member 215 has a central opening 235, each coaxial with the central opening 246 of the first electrode 206.

[0042] With respect to the third stiffener member 217 and the fourth stiffener member 219, as noted above, the third stiffener member 217 and the fourth stiffener member 219 are provided between the second film layer 224 and the second electrode 208. As discussed in more detail herein, the third stiffener member 217 and the fourth stiffener member 219 provide a gradient stiffness to gradually or incrementally increase the stiffness of the second film layer 224. As shown, the third stiffener member 217 is positioned between the second film layer 224 and the fourth stiffener member 219, and the fourth stiffener member 219 is positioned between the third stiffener member 217 and the second electrode 208.

[0043] The third stiffener member 217 and the fourth stiffener member 219 each have a geometric shape that generally corresponds to the second electrode 208. As such, the third stiffener member 217 includes a tab portion 237 and a bridge portion 239 that extends between adjacent tab portions 237 and defines an outer perimeter 241. Similarly, the fourth stiffener member 219 includes a tab portion 243 and a bridge portion 245 that extends between adjacent tab portions 243 and defines an outer perimeter 247. However, the third stiffener member 217 and the fourth stiffener member 219 are dimensionally smaller than the second electrode 208. Specifically, the fourth stiffener member 219 is dimensionally smaller than the second electrode 208, and the third stiffener member 217 is dimensionally smaller than the fourth stiffener member 219. In embodiments in which the second electrode 208 has a central opening 268, the third stiffening member 217 has a central opening 249 and the fourth stiffening member 219 has a central opening 251, each coaxial with the central opening 268 of the second electrode 208.

[0044] In embodiments, stiffening members 213, 215, 217, and 219 are each biaxially oriented polypropylene layers having a thickness of 1 mil to 2 mils, such as 1 mil, 1.5 mil, or 2 mils, or any range of thicknesses between any two of these values. In embodiments, only one of first stiffening member 213 and second stiffening member 215 is provided between first film layer 222 and first electrode 206. Furthermore, in embodiments, first stiffening member 213 and second stiffening member 215 may be a one-piece monolithic member, such that the thickness of the monolithic member at the end opposite the central opening is less than the thickness of the monolithic member at the central opening. The thickness may gradually or incrementally increase in the length direction from the opposite end toward the central opening. Similarly, in embodiments, only one of third stiffening member 217 and fourth stiffening member 219 is provided between second film layer 224 and second electrode 208. Additionally, in embodiments, the third stiffening member 217 and the fourth stiffening member 219 may be a one-piece monolithic member such that the thickness of the monolithic member at the end opposite the central opening is less than the thickness of the monolithic member at the central opening, and the thickness may increase gradually or incrementally in the length direction from the opposite end toward the central opening.

[0045] 5 , the first and second electrical insulator layers 210, 212 have geometric shapes that generally correspond to the first and second electrodes 206, 208, respectively. As such, the first and second electrical insulator layers 210, 212 each have tab portions 270, 272 and bridge portions 274, 276 that correspond to the same portions of the first and second electrodes 206, 208. Furthermore, the first and second electrical insulator layers 210, 212 each have outer perimeters 278, 280 that correspond to the outer perimeter 238 of the first electrode 106 and the outer perimeter 260 of the second electrode 108, respectively, when positioned over the first and second electrodes 206, 208.

[0046] It should be understood that in some embodiments, first electrical insulator layer 210 and second electrical insulator layer 212 generally comprise the same structure and composition. As such, in some embodiments, first electrical insulator layer 210 and second electrical insulator layer 212 each comprise adhesive surfaces 282, 284 and opposing non-sealable surfaces 286, 288, respectively. In some embodiments, first electrical insulator layer 210 and second electrical insulator layer 212 are each polymeric tapes adhered to inner surface 228 of first electrode 206 and inner surface 250 of second electrode 208, respectively.

[0047] 6, a top view of artificial muscle 200 is shown in assembled form with first terminal 230 of first electrode 206 and second terminal 252 of second electrode 208, i.e., first film layer 222 and second film layer 224, extending past the outer periphery of housing 202. As shown, second electrode 208 is laminated on top of first electrode 206; therefore, only second film layer 224, third stiffening member 217, fourth stiffening member 219, and second electrode 208 are illustrated, as other components are hidden in this view.

[0048] 7 , in the assembled configuration, first electrode 206, second electrode 208, first electrical insulator layer 210, and second electrical insulator layer 212 are sandwiched between first film layer 222 and second film layer 224. Additionally, first stiffening member 213 and second stiffening member 215 are positioned between first film layer 222 and first electrode 206, and third stiffening member 217 and fourth stiffening member 219 are positioned between second film layer 224 and second electrode 208. First film layer 222 is partially sealed to second film layer 224 in areas surrounding outer perimeter 238 of first electrode 206 and outer perimeter 260 of second electrode 208. Specifically, in some embodiments, first film layer 222 is sealed to second film layer 224 to define a sealed portion 290 that surrounds first electrode 206 and second electrode 208. In some embodiments, first film layer 222 is heat sealed to second film layer 224. However, first film layer 222 and second film layer 224 may be sealed in any suitable manner, such as using an adhesive or the like.

[0049] First electrical insulator layer 210 and second electrical insulator layer 212 provide a barrier that prevents a portion of first film layer 222 from sealing to an opposing portion of second film layer 224, thereby forming unsealed portion 292. Unsealed portion 292 of housing 202 includes electrode region 294, where electrode pair 204 is provided, and expandable fluid region 296 that is surrounded by electrode region 294. Central openings 246, 268 of first electrode 206 and second electrode 208 and central openings of the stiffener member define expandable fluid region 296 and are arranged to be axially stacked on top of each other. Although not shown, housing 202 can be cut to fit the geometric shape of first electrical insulator layer 210 and second electrical insulator layer 212 and to reduce the size of artificial muscle 200, i.e., the size of sealed portion 290.

[0050] A dielectric fluid 298, such as dielectric fluid 198, is provided within the unsealed portion 292 and flows freely between the first electrode 206 and the second electrode 208. Similar to the artificial muscles 100 discussed herein, the artificial muscle 200 is actuable between an unactuated state and an actuated state. In the unactuated state, the first electrode 206 and the second electrode 208 are partially spaced apart from each other proximate their central openings 246, 268 and the first ends 234, 256 of the tab portions 232, 254, as shown in FIG. 7 . The second ends 236, 258 of the tab portions 232, 254 remain in place relative to each other due to the housing 202 being sealed at the outer perimeter 238 of the first electrode 206 and the outer perimeter 260 of the second electrode 208. 8 , the first electrode 206 and the second electrode 208 are in contact with each other and oriented parallel to each other, forcing the dielectric fluid 298 into the expandable fluid region 296. This causes the dielectric fluid 298 to flow through the central openings 246, 268 of the first electrode 206 and the second electrode 208, expanding the expandable fluid region 296. Specifically, it should be appreciated that the first stiffener member 213 and the second stiffener member 215 cause the first film layer 222 to become progressively more stiff within the electrode region 294 in a direction toward the expandable fluid region 296. Similarly, the third stiffener member 217 and the fourth stiffener member 219 cause the second film layer 224 to become progressively more stiff within the electrode region 294 in a direction toward the expandable fluid region 296. As such, during actuation of the electrode pair 204, the least stiff portions of the first film layer 222 and the second film layer 224, i.e., the portions that do not have any stiffening members 213, 215, 217, 219, are initially attracted toward each other by actuation of the electrode pair 204. Subsequently, adjacent portions of the first film layer 222 and the second film layer 224 that have a stiffness greater than the least stiff portions, i.e., the portions that include only the second stiffening member 215 or the fourth stiffening member 219 between them, are attracted toward each other.The remaining portions of the first and second film layers 222, 224 having the greatest stiffness, i.e., the portions including the stiffening members 213, 215, 217, 219 therebetween, are then attracted toward each other, as shown in Figure 8. It should be appreciated that increasing the stiffness of the first and second film layers 222, 224 in a direction toward the expandable fluid region 296 encourages the electrodes to "zip" from the second ends 236, 258 of the tab portions 232, 254 of the first and second electrodes 206, 208 toward the first ends 234, 256 of the tab portions 232, 254 of the first and second electrodes 206, 208.

[0051] 7 , the artificial muscle 200 is shown in an unactuated state. The electrode pair 204 is provided within the electrode region 294 of the unsealed portion 292 of the housing 202. The central opening 246 of the first electrode 206 and the central opening 268 of the second electrode 208 are coaxially aligned within the expandable fluid region 296. In the unactuated state, the first electrode 206 and the second electrode 208 are partially spaced apart from each other and non-parallel to each other. Due to the first film layer 222 being sealed to the second film layer 224 around the electrode pair 204, the second ends 236, 258 of the tab portions 232, 254 are in contact with each other. Thus, the dielectric fluid 298 is provided between the first electrode 206 and the second electrode 208, thereby separating the first ends 234, 256 of the tab portions 232, 254 proximal to the expandable fluid region 196. In other words, the distance between the first end 234 of the tab portion 232 of the first electrode 206 and the first end 256 of the tab portion 254 of the second electrode 208 is greater than the distance between the second end 236 of the tab portion 232 of the first electrode 206 and the second end 258 of the tab portion 254 of the second electrode 208. In some embodiments, the first electrode 206 and the second electrode 208 may be flexible. 7, the first electrode 206 and the second electrode 208 are convex such that the second ends 236, 258 of their tab portions 232, 254 may remain close to each other but are spaced apart from each other proximal to the central openings 246, 268. In the unactuated state, the expandable fluid region 296 has a height B1.

[0052] When actuated, as shown in FIG. 8 , the first electrode 206 and the second electrode 208 zip toward each other from the second ends 244, 258 of their tab portions 232, 254, thereby forcing the dielectric fluid 298 into the expandable fluid region 296. As shown, in the actuated state, the first electrode 206 and the second electrode 208 are parallel to each other. In the actuated state, the dielectric fluid 298 flows into the expandable fluid region 296, causing it to expand. As such, the first film layer 222 and the second film layer 224 expand in opposite directions. In the actuated state, the expandable fluid region 296 has a height B2, which is greater than the height B1 of the expandable fluid region 296 when in the unactuated state. Note that, although not shown, the electrode pair 204 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 296 as needed.

[0053] A voltage is applied by a power source to move the first electrode 206 and the second electrode 208 toward each other. In some embodiments, a voltage of up to 10 kV can be provided by the power source to induce an electric field through the dielectric fluid 298. The resulting attractive force between the first electrode 206 and the second electrode 208 forces the dielectric fluid 298 into the expandable fluid region 296. Pressure from the dielectric fluid 298 within the expandable fluid region 296 causes the first film layer 222 and the first electrical insulator layer 210 to deform in a first axial direction along the central axis C of the first electrode 206 and the second film layer 224 and the second electrical insulator layer 212 to deform in an opposite second axial direction along the central axis C of the second electrode 208. When the voltage supplied to the first electrode 206 and the second electrode 208 is discontinued, the first electrode 206 and the second electrode 208 return to their initial non-parallel position in the unactuated state.

[0054] It should be appreciated that the present embodiments disclosed herein, specifically the tab portions 232, 254 with the interconnecting bridge portions 274, 276, offer several improvements over actuators such as HASEL actuators that do not include the tab portions 232, 254. An embodiment of the artificial muscle 200 that includes two pairs of tab portions 232, 254 on each of the first electrode 206 and the second electrode 208, reduces the overall mass and thickness of the artificial muscle 200, reduces the amount of voltage required during actuation, and reduces the total volume of the artificial muscle 200 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 232, 254 of the artificial muscle 200 provide a zipping front that results in increased actuation power by providing localized and uniform hydraulic actuation of the artificial muscle 200 compared to HASEL actuators that include donut-shaped electrodes. Specifically, a pair of tab portions 232, 254 provides twice the amount of actuator power per unit volume compared to a donut-shaped HASEL actuator, while two pairs of tab portions 232, 254 provide four times the amount of actuator power per unit volume. The bridge portions 274, 276 interconnecting the tab portions 232, 254 also limit buckling of the tab portions 232, 254 by maintaining the distance between adjacent tab portions 232, 254 during actuation. Because the bridge portions 274, 276 are integrally formed with the tab portions 232, 254, they also prevent leakage between the tab portions 232, 254 by eliminating adhesion points that increase the risk of blockage.

[0055] In operation, when the artificial muscle 200 is actuated by providing a voltage, the expansion of the expandable fluid region 296 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 cm3 7N.mm or more per cm 3 Such as 8 N.mm or more per unit load, or the like. Providing a voltage can include generating a voltage, for example, in embodiments where the power source is a battery, converting a voltage, for example, in embodiments where the power source is a power adapter, or any other known or yet to be developed technique for preparing a voltage for application. In one example, when the artificial muscle 100 is actuated with a voltage of 9.5 kilovolts (kV), the artificial muscle 200 produces a resultant force of 5 N. In another example, when the artificial muscle 200 is actuated with a voltage of 10 kV, the artificial muscle 200 produces a 440% strain at a 500 gram load.

[0056] Furthermore, the size of the first electrode 206 and the second electrode 208 is proportional to the amount of displacement of the dielectric fluid 298. Thus, the greater the displacement desired within the expandable fluid region 296, the larger the size of the electrode pair 204 is increased relative to the size of the expandable fluid region 296. It should be understood that the size of the expandable fluid region 296 is defined by the central openings 246, 268 in the first electrode 206 and the second electrode 208. Thus, the degree of displacement within the expandable fluid region 296 can alternatively or additionally be controlled by increasing or decreasing the size of the central openings 246, 268.

[0057] 9, an actuation system 300 for moving artificial muscles, such as artificial muscles 100, 200, can be provided between an unactuated state and an actuated state. As such, actuation system 300 can include a controller 302, an operating device 304, a power source 306, and a communication path 308. Various components of actuation system 300 will now be described.

[0058] The controller 302 includes a processor 310 and a non-transitory electronic memory 312, with various components communicatively coupled. In some embodiments, the processor 310, the non-transitory electronic memory 312, and / or other components are contained within a single device. In other embodiments, the processor 310, the non-transitory electronic memory 312, and / or other components may be distributed among multiple communicatively coupled devices. The controller 302 includes a non-transitory electronic memory 312 that stores a set of machine-readable instructions. The processor 310 executes the machine-readable instructions stored in the non-transitory electronic memory 312. The non-transitory electronic memory 312 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 310. Accordingly, the operating system 300 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 312 may be implemented as a single memory module or multiple memory modules.

[0059] In some embodiments, the non-transitory electronic memory 312 includes instructions for carrying out the functions of the actuation system 300. The instructions may include instructions for operating the artificial muscles 100, 200 based on user commands.

[0060] The processor 310 may be any device capable of executing machine-readable instructions. For example, the processor 310 may be an integrated circuit, a microchip, a computer, or any other computing device. The non-transitory electronic memory 312 and the processor 310 are coupled to a communication path 308, which provides signal interconnectivity between various components and / or modules of the operating system 300. Thus, the communication path 308 may communicatively couple any number of processors to each other, enabling the modules coupled to the communication path 308 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.

[0061] 9, a communication path 308 communicatively couples a processor 310 and non-transitory electronic memory 312 of the controller 302 to several other components of the operating system 300. For example, the operating system 300 depicted in FIG. 9 includes a processor 310 and non-transitory electronic memory 312 communicatively coupled to an operating device 304 and a power source 306.

[0062] The operating device 304 allows a user to control the operation of the artificial muscles 100, 200. In some embodiments, the operating device 304 can be a switch, a toggle, a button, or any combination of controls to provide user action. As a non-limiting example, a user can activate the artificial muscles 100, 200 to an activated state by activating the control of the operating device 304 to a first position. While in the first position, the artificial muscles 100, 200 remain in an activated state. A user can switch the artificial muscles 100, 200 to a deactivated state by operating the control of the operating device 304 from the first position to a second position.

[0063] The operating device 304 is coupled to a communication path 308 such that the communication path 308 communicatively couples the operating device 304 to other modules of the actuation system 300. The operating device 304 may provide a user interface for receiving user instructions regarding certain operational configurations of the artificial muscles 100, 200. Additionally, the user instructions may include instructions to operate the artificial muscles 100, 200 only under certain conditions.

[0064] The power source 306 (e.g., a battery) provides power to the artificial muscles 100, 200. In some embodiments, the power source 306 is a rechargeable DC power source. It should be understood that the power source 306 can be a single power source or battery for providing power to the artificial muscles 100, 200. A power adapter (not shown) can be provided and electrically coupled via a wiring harness or the like for providing power to the artificial muscles 100, 200 via the power source 306. In effect, the power source 306 is a device that can receive power at one level (e.g., a first voltage, power level, or current) and output power at a second level (e.g., a second voltage, power level, or current).

[0065] In some embodiments, the actuation system 300 also includes a display device 314. The display device 314 is coupled to the communication path 308 such that the communication path 308 communicatively couples the display device 314 to other modules of the actuation system 300. The display device 314 may output notifications responsive to the actuation state of the artificial muscles 100, 200 or indications of changes in the actuation state of the artificial muscles 100, 200. Furthermore, the display device 314, in addition to providing optical information, may be a touchscreen that detects the presence and location of tactile input on a surface of the display device 314 or a surface adjacent to the display device 314. Thus, the display device 314 may include the operating device 304 and receive mechanical input directly while an optical output is provided by the display device 314.

[0066] In some embodiments, the actuation system 300 includes network interface hardware 316 for communicatively coupling the actuation system 300 to a portable device 318 via a network 320. The portable device 318 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 318 may serve to provide user commands to the controller 302 instead of the operating device 304. As such, a user may be able to control or set programs for controlling the artificial muscles 100, 200 without utilizing control of the operating device 304. Thus, the artificial muscles 100, 200 may be remotely controlled via the portable device 318, which communicates wirelessly with the controller 302 via the network 320.

[0067] From the above, what is defined herein is an artificial muscle having an electrode pair and one or more stiffening members to provide increasing stiffness of the artificial muscle toward the expandable fluid region at opposite ends of the electrode pair or at a central portion of the electrode pair. This ensures that the artificial muscle zips inward to direct dielectric fluid into the expandable fluid region on demand.

[0068] 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.

[0069] 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. The invention disclosed in this specification includes the following aspects. [Aspect 1] An artificial muscle, a housing having an electrode region and an expandable fluid region; an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; a dielectric fluid contained within the housing; a stiffening member positioned between the housing and at least one of the first electrode and the second electrode, the stiffening member increasing the stiffness of the housing in a direction from a side edge of the electrode region toward the expandable fluid region; Equipped with the electrode pair is actuable between an unactuated state and an actuated state such that actuation from the unactuated state to the actuated state directs the dielectric fluid toward the expandable fluid region. Artificial muscles. [Aspect 2] 10. The artificial muscle of embodiment 1, further comprising a stiffening member positioned between the housing and each of the first electrode and the second electrode. Aspect 3 10. The artificial muscle of claim 1, further comprising a pair of stiffening members positioned between the housing and at least one of the first electrode and the second electrode, a first stiffening member of the pair of stiffening members having a first length and a second stiffening member of the pair of stiffening members having a second length that is greater than the first length, and the first stiffening member being positioned between the housing and the second stiffening member. Aspect 4 3. The artificial muscle of claim 2, further comprising a pair of stiffening members positioned between the housing and each of the first electrode and the second electrode, wherein a first stiffening member of the pair of stiffening members has a first length and a second stiffening member of the pair of stiffening members has a second length that is greater than the first length, and wherein the first stiffening member is positioned between the housing and the second stiffening member. Aspect 5 2. The artificial muscle of embodiment 1, wherein the housing is a flexible housing comprising an elastomeric material. Aspect 6 6. The artificial muscle of embodiment 5, wherein the housing comprises a biaxially oriented polypropylene layer. Aspect 7 7. The artificial muscle of embodiment 6, wherein the housing comprises a pair of biaxially oriented polypropylene layers. Aspect 8 5. The artificial muscle of embodiment 4, wherein each stiffening member comprises a biaxially oriented polypropylene layer. Aspect 9 2. The artificial muscle of aspect 1, wherein the first electrode and the second electrode each comprise 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 comprises a central opening circumscribing the expandable fluid region. Aspect 10 An artificial muscle, a housing having an electrode region and an expandable fluid region; an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; a dielectric fluid contained within the housing; a pair of stiffening members positioned between the housing and each of the first and second electrodes, the pair of stiffening members increasing the stiffness of the housing in a direction from the side edges of the electrode region toward the expandable fluid region; the electrode pairs are actuable between the unactuated state and the actuated state such that actuation from the unactuated state to the actuated state decreases the distance between the electrode pairs proximate the lateral ends of the electrode region before decreasing the distance between the electrode pairs proximate the expandable fluid region. Aspect 11 11. The artificial muscle of claim 10, wherein a first stiffener member of the pair of stiffener members has a first length, a second stiffener member of the pair of stiffener members has a second length that is greater than the first length, and the first stiffener member is positioned between the housing and the second stiffener member. Aspect 12 11. The artificial muscle of embodiment 10, wherein the housing comprises a pair of biaxially oriented polypropylene layers. Aspect 13 11. The artificial muscle of embodiment 10, wherein each stiffening member comprises a biaxially oriented polypropylene layer. Aspect 14 11. The artificial muscle of aspect 10, wherein the first electrode and the second electrode each comprise 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 comprises a central opening circumscribing the expandable fluid region. Aspect 15 15. The artificial muscle of embodiment 14, wherein each of the stiffener members comprises 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 stiffener members is positioned between the two or more tab portions and comprises a central opening circumscribing the expandable fluid region. Aspect 16 1. A method for actuating an artificial muscle, comprising: providing a voltage using a power source electrically coupled to an electrode pair of an artificial muscle, the artificial muscle comprising: a housing having an electrode region and an expandable fluid region; the electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; a dielectric fluid contained within the housing; providing a voltage comprising a stiffening member positioned between the housing and at least one of the first electrode and the second electrode, the stiffening member increasing the stiffness of the housing in a direction from a side edge of the electrode region toward the expandable fluid region; applying the voltage to the electrode pair of the artificial muscle, thereby actuating the electrode pair from an unactuated state to an actuated state, such that the dielectric fluid is directed into the expandable fluid region of the housing and expands the expandable fluid region; A method comprising: Aspect 17 The method of claim 16, wherein the housing comprises a first film layer and a second film layer, the first film layer and the second film layer being partially heat-sealed to each other to define a sealed portion of the housing, the housing further comprising a non-sealed portion surrounded by the sealed portion, and the electrode region and the expandable fluid region of the housing being disposed in the non-sealed portion. Aspect 18 A method according to aspect 16, wherein a pair of stiffening members are positioned between the housing and each of the first electrode and the second electrode, a first stiffening member of the pair of stiffening members having a first length, a second stiffening member of the pair of stiffening members having a second length greater than the first length, and the first stiffening member is positioned between the housing and the second stiffening member. Aspect 19 20. The method of claim 18, wherein the housing and the pair of stiffening members each comprise a biaxially oriented polypropylene layer. Aspect 20 17. The method of embodiment 16, wherein expanding the expandable fluid region results in a force greater than 4 N.mm per cm3 of actuator volume.

Claims

1. An artificial muscle, a housing having an electrode region and an expandable fluid region; an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; a dielectric fluid contained within the housing; a stiffening member positioned between the housing and at least one of the first electrode and the second electrode, the stiffening member increasing the stiffness of the housing in a direction from a side edge of the electrode region toward the expandable fluid region; and Equipped with the electrode pair is actuable between an unactuated state and an actuated state such that actuation from the unactuated state to the actuated state directs the dielectric fluid toward the expandable fluid region; a pair of stiffening members positioned between the housing and at least one of the first electrode and the second electrode, wherein a first stiffening member of the pair of stiffening members has a first length and a second stiffening member of the pair of stiffening members has a second length greater than the first length, and the first stiffening member is positioned between the housing and the second stiffening member; Artificial muscles.

2. An artificial muscle, a housing having an electrode region and an expandable fluid region; an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; a dielectric fluid contained within the housing; a stiffening member positioned between the housing and at least one of the first electrode and the second electrode, the stiffening member increasing the stiffness of the housing in a direction from a side edge of the electrode region toward the expandable fluid region; and Equipped with the electrode pair is actuable between an unactuated state and an actuated state such that actuation from the unactuated state to the actuated state directs the dielectric fluid toward the expandable fluid region; a stiffening member positioned between the housing and each of the first electrode and the second electrode; a pair of stiffening members positioned between the housing and each of the first electrode and the second electrode, wherein a first stiffening member of the pair of stiffening members has a first length and a second stiffening member of the pair of stiffening members has a second length greater than the first length, and the first stiffening member is positioned between the housing and the second stiffening member; Artificial muscles.

3. An artificial muscle, a housing having an electrode region and an expandable fluid region; an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; a dielectric fluid contained within the housing; a stiffening member positioned between the housing and at least one of the first electrode and the second electrode, the stiffening member increasing the stiffness of the housing in a direction from a side edge of the electrode region toward the expandable fluid region; and Equipped with the electrode pair is actuable between an unactuated state and an actuated state such that actuation from the unactuated state to the actuated state directs the dielectric fluid toward the expandable fluid region; 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 circumscribing the expandable fluid region. Artificial muscles.

4. The artificial muscle of claim 1 , wherein the housing is a flexible housing comprising an elastomeric material.

5. 5. The artificial muscle of claim 4, wherein the housing comprises a biaxially oriented polypropylene layer.

6. 6. The artificial muscle of claim 5, wherein the housing comprises a pair of biaxially oriented polypropylene layers.

7. 3. The artificial muscle of claim 2, wherein each stiffening member comprises a layer of biaxially oriented polypropylene.

8. An artificial muscle, a housing having an electrode region and an expandable fluid region; an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; a dielectric fluid contained within the housing; a pair of stiffening members positioned between the housing and each of the first and second electrodes, the pair of stiffening members increasing the stiffness of the housing in a direction from the side edges of the electrode region toward the expandable fluid region; the electrode pairs are actuable between the unactuated state and the actuated state such that actuation from the unactuated state to the actuated state reduces the distance between the electrode pairs proximate the lateral ends of the electrode region before the distance between the electrode pairs proximate the expandable fluid region is reduced; a first stiffening member of the pair of stiffening members having a first length and a second stiffening member of the pair of stiffening members having a second length greater than the first length, the first stiffening member being positioned between the housing and the second stiffening member; Artificial muscles.

9. An artificial muscle, a housing having an electrode region and an expandable fluid region; an electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; a dielectric fluid contained within the housing; a pair of stiffening members positioned between the housing and each of the first and second electrodes, the pair of stiffening members increasing the stiffness of the housing in a direction from the side edges of the electrode region toward the expandable fluid region; the electrode pairs are actuable between the unactuated state and the actuated state such that actuation from the unactuated state to the actuated state reduces the distance between the electrode pairs proximate the lateral ends of the electrode region before the distance between the electrode pairs proximate the expandable fluid region is reduced; 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 circumscribing the expandable fluid region. Artificial muscles.

10. The artificial muscle of claim 8 or 9, wherein the housing comprises a pair of biaxially oriented polypropylene layers.

11. 10. The artificial muscle of claim 8 or 9, wherein each stiffening member comprises a biaxially oriented polypropylene layer.

12. 10. The artificial muscle of claim 9 , wherein each of the stiffener members comprises 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 stiffener members comprises a central opening positioned between the two or more tab portions and circumscribing the expandable fluid region.

13. 1. A method for actuating an artificial muscle, comprising: providing a voltage using a power source electrically coupled to an electrode pair of an artificial muscle, the artificial muscle comprising: a housing having an electrode region and an expandable fluid region; the electrode pair including a first electrode and a second electrode positioned in the electrode region of the housing; a dielectric fluid contained within the housing; providing a voltage comprising a stiffening member positioned between the housing and at least one of the first electrode and the second electrode, the stiffening member increasing the stiffness of the housing in a direction from a side edge of the electrode region toward the expandable fluid region; applying the voltage to the electrode pair of the artificial muscle, thereby actuating the electrode pair from an unactuated state to an actuated state, such that the dielectric fluid is directed into the expandable fluid region of the housing and expands the expandable fluid region; Including, a pair of stiffening members are positioned between the housing and each of the first electrode and the second electrode, a first stiffening member of the pair of stiffening members having a first length and a second stiffening member of the pair of stiffening members having a second length greater than the first length, and the first stiffening member is positioned between the housing and the second stiffening member; method.

14. 14. The method of claim 13, wherein the housing comprises a first film layer and a second film layer, the first film layer and the second film layer being partially heat-sealed to one another to define a sealed portion of the housing, the housing further comprising a non-sealed portion surrounded by the sealed portion, and the electrode region and the expandable fluid region of the housing being disposed in the non-sealed portion.

15. The method of claim 13 , wherein the housing and the pair of stiffening members each comprise a layer of biaxially oriented polypropylene.

16. Expanding the expandable fluid region is achieved by increasing the actuator volume by a factor of cm. ３ 14. The method of claim 13, wherein the force is greater than 4 N.mm per minute.

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