ELECTROACTIVE POLYMERS THAT CONTRACT AND EXPAND, SENSE PRESSURE, AND ATTENUATE FORCE AND SYSTEMS USING THE SAME

Abstract

Novel robust electroactive polymers (EAPs) and EAP-based systems are described, which contract and expand at low voltages to provide for a shape-morphing system, which also sense mechanical pressure, from gentle touch to high impact, and which attenuate force. These EAPs and EAP-based systems can be used in a prosthetic liner, and potentially as the entire prosthetic liner, in a prosthetic hard socket, in shoe wear, sports gear, protective gear, and military gear, and in compression equipment, to contract and expand in strategic areas as needed to maintain a perfect fit, to sense pressure and provide feedback to automatically maintain perfect fit, and to attenuate force for an extremely comfortable fit.

Claims

1. An electroactive polymer-based system, comprising: a first electrode; a second electrode counter to the first electrode and spaced apart from the first electrode; an ionically conductive fluid; and an actuator electronically connected to the first electrode and in fluidic communication with the second electrode, and comprising a first electroactive ionic polymer layer comprising a first electroactive ionic polymer; and a second electroactive ionic polymer layer comprising a second electroactive ionic polymer; wherein the first and second electroactive polymers are selected to expand or contract on application of an electrical potential; wherein the Shore O durometer value of the second electroactive ionic polymer is higher than that of the first electroactive ionic polymer; and wherein the first and second electroactive ionic polymer layers are configured to transfer the force applied onto the first electroactive ionic polymer layer to the second electroactive ionic polymer layer to be attenuated.

2. The electroactive polymer-based system of claim 1, wherein the first and second electroactive ionic polymer layers are in direct contact with each other or in close proximity to each other.

3. The electroactive polymer-based system of claim 1, wherein the first and second electroactive ionic polymer layers are separated by a soft or elastic layer.

4. The electroactive polymer-based system of claim 1, wherein the difference of Shore O durometer values between the first and second electroactive ionic polymer layers is about 2-60.

5. The electroactive polymer-based system of claim 1, wherein the first electroactive ionic polymer has a cross-link density of at least about 1.5%-6.0% vol/wt of cross-linking agent/linear monomers.

6. The electroactive polymer-based system of claim 1, wherein the second electroactive ionic polymer has a cross-link density of less than about 1.5% vol/wt of cross-linking agent/linear monomers.

7. The electroactive polymer-based system of claim 1, wherein the second electroactive ionic polymer has a cross-link density of about 0.50%, 0.75%, 1.00%, 1.25%, 1.50%, 1.60%, 1.75%, 1.80%, 2.00%, 2.25%, or 2.50% higher for each cross-linking agent than that of the first electroactive ionic polymer.

8. The electroactive polymer-based system of claim 1, wherein the second electroactive ionic polymer layer has a shape selected from the group consisting of conical, half-ovoid, ovoid, sheet, pad, sphere, cylinder, cone, pyramid, prism, spheroid ellipse, ellipsoid, rectangular prism, toroid, parallelepiped, rhombic prism shapes and a combination thereof.

9. The electroactive polymer-based system of claim 1, wherein the second electroactive ionic polymer layer has a shape selected from the group consisting of a conical shape, a half-ovoid shape, an ovoid shape, and a combination thereof.

10. The electroactive polymer-based system of claim 1, wherein the first electroactive ionic polymer layer has a shape reciprocal to the shape of the second electroactive ionic polymer layer.

11. The electroactive polymer-based system of claim 1, further comprising one or more electrically conducting layers in electrical contact with the actuator and the first electrode.

12. The electroactive polymer-based system of claim 11, wherein the electroactive polymer-based system comprises a first and second electrically conducting layers in electrical contact with the first and second electroactive ionic polymer layers, respectively.

13. The electroactive polymer-based system of claim 11, wherein the electrically conducting layer comprises an array of a plurality of electrically conducting areas.

14. The electroactive polymer-based system of claim 1, further comprising a fluid reservoir in fluidic communication with the first and second electroactive ionic polymers and connected to the second electrode.

15. The electroactive polymer-based system of claim 14, wherein the fluid reservoir is in the second electroactive ionic polymer layer.

16. The electroactive polymer-based system of claim 1, wherein the first and/or second electroactive ionic polymers are each independently selected from the group consisting of polymethacrylic acid, poly-2-hydroxyethyl methacrylate, poly(vinyl alcohol), ionized poly(acrylamide), poly(acrylic acid), poly(acrylic acid)-co-(poly(acrylamide), poly(2-acrylamide-2-methyl-1-propane sulfonic acid), poly(methacrylic acid), poly(styrene sulfonic acid), quarternized poly(4-vinyl pyridinium chloride), poly(vinylbenzyltrimethyl ammonium chloride), sulfonated poly(styrene-b-ethylene-co-butylene-b-styrene), sulfonated poly(styrene), and a combination thereof.

17. The electroactive polymer-based system of claim 1, wherein the first and/or second electroactive ionic polymers are cross-linked with one or more cross-linking polymer agents each selected from the group consisting of a poly(dimethylsiloxane) (PDMS) dimethacrylate chain, a poly(ethylene glycol) dimethacrylate chain, an ethylene glycol dimethacrylate, 1,1,1-trimethylolpropane trimethacrylate, and a combination thereof.

18. The electroactive polymer-based system of claim 1, wherein the first electroactive ionic polymer is cross-linked with one or more first cross-linking polymer agents which is elastomeric or provides elasticity.

19. The electroactive polymer-based system of claim 18, wherein the first cross-linking polymeric agent comprising a poly(dimethylsiloxane) (PDMS) dimethacrylate chain.

20. The electroactive polymer-based system of claim 18, wherein the second electroactive ionic polymer is cross-linked with a second cross-linking polymeric agent selected from the group consisting of a poly(dimethylsiloxane) dimethacrylate, a poly(ethylene glycol) dimethacrylate chain, an ethylene glycol dimethacrylate, 1,1,1-trimethylolpropane trimethacrylate, and a combination thereof; wherein the second electroactive ionic polymer is cross-linked at a higher level than that of the first electroactive ionic polymer.

21. An electroactive polymer-based system, comprising: one or more first electrodes; a second electrode counter to the first electrode and spaced apart from the first electrode; an ionically conductive fluid; and an actuator electronically connected to the first electrodes and in fluidic communication with the second electrode, and comprising an electroactive ionic polymer layer comprising an electroactive ionic polymer selected to expand or contract on application of an electrical potential; and an array of a plurality of isolated conductive areas each in electric communication with a plurality of areas of the electroactive ionic polymer layer; wherein the plurality of isolated conductive areas comprises at least one or more first isolated conductive areas in electric communication with the one or more first electrodes independent from other isolated conductive areas such that the areas of the electroactive ionic polymer layer in electric communication with the first isolated conductive areas are capable of being actuated independently.

22. The electroactive polymer-based system of claim 21, wherein the electroactive polymer-based system further includes one or more third electrodes; the plurality of isolated conductive areas comprises at least one or more second isolated conductive areas in electric communication with the one or more third electrodes independent from other isolated conductive areas such that the areas of the electroactive ionic polymer layer in electric communication with the second isolated conductive areas are capable of being actuated independently.

23. A liner for securing a limb in a prosthetic device or a prosthetic socket comprising: a flexible layer configured to surround a limb of a patient or conform to the inside circumference of a prosthesis; and at least one electroactive polymer-based system of claim 1 or 21 embedded in the flexible layer and configured to secure or engage a limb of a patient.

24. The liner or prosthetic socket of claim 23, wherein the flexible layer is made of silicone.

25. The liner or prosthetic socket of claim 23, wherein the liner or prosthetic socket comprises a plurality of the electroactive polymer-based system of any one of the preceding claims and embedded in the flexible layer; wherein the electroactive polymer-based systems are fluidically isolated from each other and arranged around the limb of a patient to secure the limb.

26. The liner or prosthetic socket of claim 23, wherein the prosthesis has a hard body and upon the application of an electrical potential to the first electrode, the actuator is configured to expand against the hard body towards the limb of the patient.

27. A shoe insole comprising an electroactive polymer-based system of claim 1 or 21.

28. A protective gear comprising an electroactive polymer-based system of claim 1 or 21.

29. The protective gear of claim 28, wherein the protective gear is a helmet.

30. A compression equipment comprising an electroactive polymer-based system of claim 1 or 21.

31. The compression equipment of claim 30, wherein the compression equipment is a compression boot for diabetic patients, a military anti-shock trouser (MAST, also called pneumatic anti-shock garments (PASG)) for trauma patients, a compression bandage, a compression tape, or a compressive therapy.

Description

DESCRIPTION OF THE DRAWINGS

[0076] The invention is described with reference to the following figures, which are presented for the purpose of illustration only and are not intended to be limiting. In the Drawings:

[0077] FIG. 1A is a schematic view of an encapsulated electroactive polymer (EAP)-based system, according to one or more embodiments described herein.

[0078] FIG. 1B is a schematic view of an electroactive polymer (EAP)-based shape-morphing system, sensing, and force attenuating system, which is multi-modal or multi-layer, where the lower EAP layer is of a higher cross-link density and thus higher durometer than the upper EAP layer, and the lower EAP layer has a conical shape.

[0079] FIG. 2 is a schematic view of an EAP-based shape-morphing system, sensing, and force attenuating system, which is multi-modal or multi-layer, where the lower EAP layer is of a higher cross-link density and thus higher durometer than the upper EAP layer, and the lower EAP layer has a half-ovoid shape.

[0080] FIG. 3 is a schematic view of an encapsulated EAP-based shape-morphing, sensing, and force attenuating system as a pad for the prosthetic liner or socket, according to one or more embodiments described herein.

[0081] FIG. 4 is a schematic view of an encapsulated EAP-based shape-morphing, sensing, and force attenuating system for shoe insoles, for example, with conductive layers above and below the EAP layer, where the conductive layer(s) can be pixelated.

[0082] FIG. 5 is a cross-sectional view of an encapsulated EAP-based shape-morphing, sensing, and force attenuating system within a flexible prosthetic liner, according to one or more embodiments described herein.

[0083] FIG. 6 is a schematic view of an encapsulated EAP-based shape-morphing, sensing, and force attenuating system within a flexible prosthetic liner, according to one or more embodiments described herein.

[0084] FIG. 7 is a schematic view of an encapsulated EAP-based shape-morphing, sensing, and force attenuating system within a prosthetic hard socket, according to one or more embodiments described herein.

[0085] FIG. 8 is a schematic view of an encapsulated EAP-based shape-morphing, sensing, and force attenuating system as a band in the prosthetic liner or prosthetic socket, according to one or more embodiments described herein.

[0086] FIG. 9 is a schematic view of an encapsulated EAP-based shape-morphing, sensing, and force attenuating system as a band in the prosthetic socket, according to one or more embodiments described herein.

[0087] FIG. 10 is a schematic view of an encapsulated EAP-based EAP shape-morphing, sensing, and force attenuating system as a band in the prosthetic liner, according to one or more embodiments described herein.

[0088] FIG. 11 is a schematic view of an encapsulated EAP-based EAP shape-morphing, sensing, and force attenuating system as a compression boot, according to one or more embodiments described herein.

[0089] FIG. 12 is a transparent view of an encapsulated EAP-based shape-morphing, sensing, and force attenuating system as a compression boot, according to one or more embodiments described herein.

[0090] FIG. 13 is a schematic view of an encapsulated EAP-based shape-morphing, sensing, and force attenuating system as compression tape, according to one or more embodiments described herein.

[0091] FIG. 14 illustrates drop tower data comparing EAPs in the instant invention (EAP samples in the instant invention are the RasFlex series) to traditional padding in Xenith and Riddell football helmets, according to one or more embodiments described herein.

[0092] FIG. 15 illustrates the compression testing of EAP Sample LA_12 using an Instron Model 4466 Universal Testing Machine, at a speed of 3 mm/min with a peak compressive force of 174.964 N, according to one or more embodiments described herein.

[0093] FIG. 16 illustrates cyclic stress-strain testing of EAP Sample LR_97_BJ using a Universal Testing Machine to 50% elongation, according to one or more embodiments described herein.

DETAILED DESCRIPTION

[0094] In one aspect, an electroactive polymer-based system is described, including:

a first electrode;

[0095] a second electrode counter to the first electrode and spaced apart from the first electrode;

[0096] an ionically conductive fluid; and

[0097] an actuator electronically connected to the first electrode and in fluidic communication with the second electrode, and comprising [0098] a first electroactive ionic polymer layer comprising a first electroactive ionic polymer; and [0099] a second electroactive ionic polymer layer comprising a second electroactive ionic polymer; wherein the first and second electroactive polymers are selected to expand or contract on application of an electrical potential; wherein the durometer value of the second electroactive ionic polymer is higher than that of the first electroactive ionic polymer; and wherein the first and second electroactive ionic polymer layers are configured to transfer the force applied onto the first electroactive ionic polymer layer to the second electroactive ionic polymer layer to be attenuated.

[0100] The phrase durometer value or durometer, as used herein, refers to the measurement of hardness of a material, where the numerical value, between 0 and 100, defines the hardness or softness of a material. Higher numbers indicate harder materials; lower numbers indicate softer materials. Durometer is typically used as a measure of hardness in polymers, elastomers, and rubbers. Durometer measures the depth of an indentation in the material created by a given force on a standardized pressure foot. A standard way of determining the durometer value of an EAP layer is to place an EAP sample that is at least 6.4 mm thick on top of a hard surface, and then used the durometer instrument to measure the durometer value by pressing the pressure foot on the top area of the EAP and noting the durometer value on the scale. Durometer comes in 12 different scales. The EAPs in the instant invention are typically measured using the Shore O and the Shore OO scale, to determine hardness in these relatively soft materials.

[0101] In certain embodiments, the actuator is apart from the second electrode. In certain embodiments, the electroactive polymer-based system further includes an electrically conducting backing or a conductive layer disposed along and in electrical contact with a surface of the actuator. The conducting backing or a conductive layer may be bonded to a surface of the actuator. Any level/manner of bonding is contemplated.

[0102] The EAP-based system disclosed herein is now described with reference to FIG. 1A. FIG. 1A shows an encapsulated electroactive polymer (EAP)-based system encapsulated in a flexible encapsulating coating 6. The EAP-based system includes a first electrode 20, a second electrode 21 counter to the first electrode and spaced apart from the first electrode 20, an ionically conductive fluid in the fluidic reservoir 19, and an actuator 3 including one or more EAP shape-morphing, sensing, and force attenuating layer which is electronically connected to the first electrode 20 through a conductive layer 5 and in fluidic communication with the second electrode 21. The EAP polymers are selected to expand or contract on application of an electrical potential. The fluidic reservoir 19 can be located in any other part of the EAP-based system. In some embodiments, the fluidic reservoir 19 can be between the upper and lower EAP layers as described below. In some embodiments, the fluidic reservoir 19 can be the second EAP layer or part of the second EAP layer.

[0103] In some embodiments, because these EAPs, in order to be electroactive, need to be moist and contain an electrolyte, the electroactive material may be further swollen with an electrolyte solution or electrolyte gel formulation. Other suitable materials and compositions for the electroactive material are described in U.S. Pat. Nos. 8,088,453, 7,935,743, and 5,736,590 and U.S. Ser. Nos. 13/843,959 and 14/476,646, the contents of which are expressly incorporated by reference.

[0104] In some embodiments, the actuator 3 described in FIG. 1A includes a first electroactive ionic polymer layer comprising a first electroactive ionic polymer; and a second electroactive ionic polymer layer comprising a second electroactive ionic polymer; wherein the first and second electroactive polymers are selected to expand or contract on application of an electrical potential; wherein the durometer value of the second electroactive ionic polymer is higher than that of the first electroactive ionic polymer; and wherein the first and second electroactive ionic polymer layers are configured to transfer the force applied onto the first electroactive ionic polymer layer to the second electroactive ionic polymer layer to be attenuated.

[0105] The multi-layer EAP-based actuator disclosed herein is now described with reference to FIGS. 1B and 2. FIG. 1B shows an electroactive polymer (EAP)-based system (left hand side), where the multi-modality for force attenuation is displayed (right hand side). The EAP-based system includes two EAP layers (1 and 2). The lower EAP layer 2 is of a higher cross-link density and thus higher durometer than the upper EAP layer 1. This multi-modal/multi-layer EAP system can have a conductive layer (which may be electrically connected to an electrode) above and below the EAP system for sensing and shape-morphing, and can be encapsulated, with a flexible silicone layer, for example. The lower layer 2 (e.g., a more cross-linked layer) would be closer to the head for helmets, bottom of the feet for shoe soles, or to any part of the body for padding. The upper layer (less cross-linked layer) would be closer to the outside environment. The lower EAP layer has a conical shape and the upper EAP layer has a reciprocal shape. This design allows for more force to be deflected laterally rather than through the system. However, any other shapes known in the art are contemplated.

[0106] FIG. 2 shows an electroactive polymer (EAP)-based system (left hand side), where the multi-modality for force attenuation is displayed (right hand side). The lower EAP layer 2 is of a higher cross-link density and thus higher durometer than the upper EAP layer 1. This multi-modal EAP system can have a conductive layer (which may be electrically connected to an electrode) above and below the EAP system for sensing and shape-morphing, and can be encapsulated, with a flexible silicone layer, for example. The lower layer 2 (more cross-linked layer) would be closer to the head for helmets, bottom of the feet for shoe soles, or to any part of the body for padding. The upper layer 1 (less cross-linked layer) would be closer to the outside environment. The lower EAP layer 2 has a half-ovoid shape and the upper EAP layer has a reciprocal shape. This design allows for more force to be deflected laterally rather than through the system. However, any other shapes known in the art are contemplated.

[0107] Non-limiting examples of the shapes for the lower EAP layer (also referred to as the second electroactive ionic polymer layer) include a shape selected from the group consisting of conical, half-ovoid, ovoid, sheet, pad, sphere, cylinder, cone, pyramid, prism, spheroid ellipse, ellipsoid, rectangular prism, toroid, parallelepiped, rhombic prism and a combination thereof. In some embodiments, the upper EAP layer (also referred to as the first electroactive ionic polymer layer) has a shape reciprocal to the shape of the lower EAP layer. In some embodiments, the two EAP layers (1 and 2) are in direct contact with each other or in close proximity to each other so that the force applied onto the upper layer 1 (lower durometer value) is transferred to the lower layer (higher durometer value) to be attenuated, and the force is dispersed laterally. In other embodiments, the two EAP layers (1 and 2) are not in direct contact but are separated by a soft or elastic layer so that through the soft or elastic layer, the force applied onto the upper layer 1 (lower durometer value) is transferred to the lower layer (higher durometer value) to be attenuated. The soft or elastic layer can be porous to allow electrolyte to pass through to maintain fluid communication. In some embodiments, the soft or elastic layer can serve as the fluidic reservoir 19 described in FIG. 1A.

[0108] In some embodiments, the lower EAP layer (also referred to as the second EAP layer) has a durometer value of about at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 higher than that of the upper EAP layer (also referred to as the first EAP layer). In some embodiments, the durometer value difference between the first and second EPA layers is in a range bounded by any two numbers disclosed above.

[0109] In some embodiments, the durometer value difference between the first and second EPA layers is about 2-60, 2-55, 2-50, 2-45, 2-40, 2-35, 2-30, 2-25, 2-20, 2-15, 2-10, 2-9, 2-8, 2-7, 2-6, 2-5, 2-4, 2-3. In some embodiments, the durometer value difference between the first and second EPA layers is about 3-60, 3-55, 3-50, 3-45, 3-40, 3-35, 3-30, 3-25, 3-20, 3-15, 3-10, 3-9, 3-8, 3-7, 3-6, 3-5, or 3-4. In some embodiments, the durometer value difference between the first and second EPA layers is about 4-60, 4-55, 4-50, 4-45, 4-40, 4-35, 4-30, 4-25, 4-20, 4-15, 4-10, 4-9, 4-8, 4-7, 4-6, or 4-5. In some embodiments, the durometer value difference between the first and second EPA layers is about 5-60, 5-55, 5-50, 5-45, 5-40, 5-35, 5-30, 5-25, 5-20, 5-15, 5-10, 5-9, 5-8, 5-7, or 5-6. In some embodiments, the durometer value difference between the first and second EPA layers is about 6-60, 6-55, 6-50, 6-45, 6-40, 6-35, 6-30, 6-25, 6-20, 6-15, 6-10, 6-9, 6-8, or 6-7. In some embodiments, the durometer value difference between the first and second EPA layers is about 7-60, 7-55, 7-50, 7-45, 7-40, 7-35, 7-30, 7-25, 7-20, 7-15, 7-10, 7-9, or 7-8. In some embodiments, the durometer value difference between the first and second EPA layers is about 8-60, 8-55, 8-50, 8-45, 8-40, 8-35, 8-30, 8-25, 8-20, 8-15, 8-10, or 8-9. In some embodiments, the durometer value difference between the first and second EPA layers is about 9-60, 9-55, 9-50, 9-45, 9-40, 9-35, 9-30, 9-25, 9-20, 9-15, or 9-10. In some embodiments, the durometer value difference between the first and second EPA layers is about 10-60, 10-55, 10-50, 10-45, 10-40, 10-35, 10-30, 10-25, 10-20, or 10-15. In some embodiments, the durometer value difference between the first and second EPA layers is about 15-60, 15-55, 15-50, 15-45, 15-40, 15-35, 15-30, 15-25, or 15-20. In some embodiments, the durometer value difference between the first and second EPA layers is about 20-60, 20-55, 20-50, 20-45, 20-40, 20-35, 20-30, or 20-25. In some embodiments, the durometer value difference between the first and second EPA layers is about 25-60, 25-55, 25-50, 25-45, 25-40, 25-35, or 25-30. In some embodiments, the durometer value difference between the first and second EPA layers is about 30-60, 30-55, 30-50, 30-45, 30-40, or 30-35. In some embodiments, the durometer value difference between the first and second EPA layers is about 35-60, 35-55, 35-50, 35-45, or 35-40. In some embodiments, the durometer value difference between the first and second EPA layers is about 40-60, 40-55, 40-50, or 40-45. In some embodiments, the durometer value difference between the first and second EPA layers is about 45-60, 45-55, or 45-50. In some embodiments, the durometer value difference between the first and second EPA layers is about 50-60, 50-55 or 55-60.

[0110] In some embodiments, the upper EAP layer (also referred to as the first EAP layer) has a Shore O durometer value of about 2-25. In some embodiments, the lower EAP layer (also referred to as the EAP second layer) has a Shore O durometer value of about 15-60.

[0111] In some embodiments, the lower EAP layer (also referred to as the second EAP layer) has a cross-link density of at least 1.5% vol/wt of cross-linking agent/linear monomers (e.g., with poly(ethylene glycol) dimethacrylate) and at least 6% vol/wt of cross-linking agent/linear monomers (e.g., with poly(dimethylsiloxane) dimethacrylate). In some embodiments, the upper EAP layer (also referred to as the first EAP layer) has a cross-link density of less than 1.5% vol/wt of cross-linking agent/linear monomers (e.g., with poly(ethylene glycol) dimethacrylate) and less than 6% vol/wt of cross-linking agent/linear monomers (e.g., with poly(dimethylsiloxane) dimethacrylate). In some embodiments, the lower EAP layer (also referred to as the second EAP layer) has a cross-link density of about 1.00%, 1.25%, 1.50%, 1.60%, 1.75%, 1.80%, 2.00%, 2.25%, or 2.50% higher for each cross-linking agent than that of the upper EAP layer (also referred to as the first EAP layer). In some embodiments, a small change in cross-link density causes a large change in the EAPs physical properties such as durometer.

[0112] In some embodiments, the first and/or second electroactive ionic polymers are selected from the group consisting of polymethacrylic acid, poly2-hydroxyethyl methacrylate, poly(vinyl alcohol), ionized poly(acrylamide), poly(acrylic acid), poly(acrylic acid)-co-poly(acrylamide), poly(2-acrylamide-2-methyl-1-propane sulfonic acid), poly(methacrylic acid), poly(styrene sulfonic acid), quarternized poly(4-vinyl pyridinium chloride), poly(vinylbenzyltrimethyl ammonium chloride), sulfonated poly(styrene-b-ethylene-co-butylene-b-styrene), sulfonated poly(styrene), and a combination thereof.

[0113] In some embodiments, the first and/or second electroactive ionic polymers are cross-linked with one or more cross-linking polymer agents each selected from the group consisting of a poly(dimethylsiloxane) (PDMS) dimethacrylate chain, a poly(ethylene glycol) dimethacrylate chain, an ethylene glycol dimethacrylate, 1,1,1-trimethylolpropane trimethacrylate, and a combination thereof. In some embodiments, the first and second electroactive polymers are cross-linked with different cross-linking agents and/or combinations of cross-lining agents so that the durometer value of the second electroactive ionic polymer is higher than that of the first electroactive ionic polymer.

[0114] In some specific embodiments, the first electroactive ionic polymer is cross-linked with one or more first cross-linking polymer agents which provides elasticity in the final EAP. Non-limiting examples of elastomeric causing cross-linking agents include poly(dimethylsiloxane) (PDMS) dimethacrylate. In some specific embodiments, the second electroactive ionic polymer is cross-linked with a second cross-linking polymeric agent selected from the group consisting of a poly(ethylene glycol) dimethacrylate chain, an ethylene glycol dimethacrylate, 1,1,1-trimethylolpropane trimethacrylate, and a combination thereof. In some specific embodiments, the second electroactive ionic polymer is cross-linked with poly(dimethylsiloxane) (PDMS) dimethacrylate and one or more other cross-linking agent selected from the group consisting of a poly(ethylene glycol) dimethacrylate chain, an ethylene glycol dimethacrylate, 1,1,1-trimethylolpropane trimethacrylate, and a combination thereof, such that the durometer value of the second electroactive ionic polymer is higher than that of the first electroactive ionic polymer.

[0115] In some embodiments, one or both of the lower and upper EAP layers are in electrical contact with a conductive layer electrically connected to an electrode (also referred to as the first electrode). In some embodiments, the conductive layer is made from a material selected from the group consisting of metal, carbon, and a combination thereof.

[0116] In some embodiments, the electroactive polymer-based system also includes a second electrode counter to the first electrode. In some embodiments, the first and/or second electrodes are flexible, bendable or stretchable electrodes. In some embodiments, the first and/or second electrodes are spiral-shaped or spring-shaped. In some embodiments, the first and/or second electrodes are made from a material selected from the group consisting of metal, carbon, other conductive materials, and a combination thereof. For simplicity, these elements, e.g., the first and second electrodes, conductive layers are not shown in FIGS. 1B and 2.

[0117] FIG. 3 shows the encapsulated EAP shape-morphing, sensing, and force attenuating system as a pad for the prosthetic liner or socket, where the lower (or outer) layer 15 of the pad comprises a firmer much less shape morphing (higher cross-link density) EAP zone, encapsulated in a flexible coating 6. The upper (or inner layer) of the pad 14 comprises a softer, much more shape-morphing (lower cross-link density) EAP zone. Alternatively, the lower layer 15 can be an open-cell foam reservoir. There can be additional open cell foam reservoirs for fluidic storage and fluidic flow. The two layers are separated by a conductive layer 5.

[0118] In another aspect, an electroactive polymer-based system is described, including:

[0119] one or more first electrodes;

[0120] a second electrode counter to the first electrode and spaced apart from the first electrode;

[0121] an ionically conductive fluid; and

[0122] an actuator electronically connected to the first electrodes and in fluidic communication with the second electrode, and comprising [0123] an electroactive ionic polymer layer comprising an electroactive ionic polymer selected to expand or contract on application of an electrical potential; and [0124] an array of a plurality of isolated conductive areas each in electric communication with an area of a plurality of areas of the electroactive ionic polymer layer; wherein the plurality of isolated conductive areas comprises at least one or more first isolated conductive areas in electric communication with the one or more first electrodes independent from other isolated conductive areas such that the areas of the electroactive ionic polymer layer in electric communication with the first isolated conductive areas are capable of being actuated independently.

[0125] In some embodiments, the electroactive polymer-based system further includes one or more third electrodes in electric communication with one or more second isolated conductive areas in the plurality of isolated conductive areas such that the areas of the electroactive ionic polymer layer in electric communication with the second isolated conductive areas are capable of being actuated independently from areas in the EAP layer in electric communication with the first isolated conductive areas.

[0126] FIG. 4 shows an encapsulated EAP shape-morphing, sensing, and force attenuating system for shoe insoles, for example, with conductive layer 5 (which can be lined electrically to the first electrode) below the EAP layer 3, and a conductive layer above the EAP layer 3 and including an array of a plurality of isolated small (pixelated) conductive areas. This allows for shape-morphing in desired areas, by separately applying electric potential to one or more of the conductive areas. This also allows for sensing, from simple sensing, such as number of steps, to sophisticated pressure map sensing of the foot and foot strike during ambulation (walking and running) using pixilation of one or both conductive layers. The conductive layers can be carbon based particles, fibers, and/or weaves, or metal based particles, wires, or meshes, or a combination thereof. The EAPs being a non-Newtonian material (is a semi-solid hydrogel, with solid and liquid properties) also attenuates force, providing for a comfortable, healthy shoe insole.

[0127] FIG. 5 shows an encapsulated EAP shape-morphing, sensing, and force attenuating system within a flexible prosthetic liner, where the EAP system shape-morphs for perfect fit, senses pressure to maintain perfect fit through an algorithm, and attenuates force, with good creep resistance and low hysteresis effects, for an extremely comfortable fit, particularly during ambulation (walking and running).

[0128] FIG. 6 shows the encapsulated EAP shape-morphing, sensing, and force attenuating system 8 within a flexible prosthetic liner, where the EAP system shape-morphs for perfect fit, senses pressure to maintain perfect fit through an algorithm, and attenuates force, with good creep resistance and low hysteresis effects, for an extremely comfortable fit, particularly during ambulation (walking and running) Also shown is a battery pack 11, which can have a three-way switch for EAP contraction, EAP expansion, and no electric input.

[0129] FIG. 7 is a cross-sectional of the encapsulated EAP shape-morphing, sensing, and force attenuating system 8 as pads in strategic locations within a prosthetic hard socket 12, where the EAP-based pads shape-morph for perfect fit, senses pressure to maintain perfect fit through an algorithm, and attenuates force, with good creep resistance and low hysteresis effects, for an extremely comfortable fit, particularly during ambulation (walking and running) Not shown are battery packs and switches, which can have a three-way switch for EAP contraction, EAP expansion, and no electric input.

[0130] FIG. 8 shows an encapsulated EAP shape-morphing, sensing, and force attenuating system as a band in the prosthetic liner or prosthetic socket, where there are alternating zones within the band of more shape-morphing EAPs 14 (less cross-linked) and less shape-morphing EAPs 15 (more cross-linked) or open-cell foams. This can be expanded to describe an entire prosthetic liner comprising the EAP shape-morphing, sensing, and force attenuating materials, with different zones for different levels of desired shape-morphing abilities. Not shown is encapsulation, wiring, battery packs, and switches.

[0131] FIG. 9 shows the encapsulated EAP shape-morphing, sensing, and force attenuating system as an EAP band 16 in the prosthetic hard socket, located within the circumference of the prosthetic socket 12 to maintain fit around the residual limb. Not shown is wiring, battery packs, and switches.

[0132] FIG. 10 shows the encapsulated EAP shape-morphing, sensing, and force attenuating system as an EAP band 16 in the prosthetic liner 7, located within the circumference of the prosthetic liner to maintain fit around the residual limb. Not shown is wiring, battery packs, and switches.

[0133] FIG. 11 shows the encapsulated EAP shape-morphing, sensing, and force attenuating system as a compression boot, where one or more layers of the EAP-based system comprising a conductive layer 5 and EAP layer 3, all encapsulated, compress the foot and/or leg. This can be programmed to compress the foot and/or leg in circumferential wave-like pattern(s), to massage and push excess fluid out of the limb towards the central body.

[0134] FIG. 12 shows the encapsulated EAP shape-morphing, sensing, and force attenuating system as a compression boot, in zones within the boot, including a plurality of EAP-based zones 8. Each of the EAP-based zone 8 may comprise a conductive layer and EAP layer, all encapsulated, compress the foot and/or leg. This can be programmed to compress the foot and/or leg in circumferential wave-like pattern(s), to massage and push excess fluid out of the limb towards the central body.

[0135] FIG. 13 shows the encapsulated EAP shape-morphing, sensing, and force attenuating system as compression tape, where one or more layers of the EAP-based system comprising a conductive layer 5 and EAP layer 3, all encapsulated, create a dynamic compressive tape or bandage. This can be programmed to compress the foot and/or leg in circumferential wave-like pattern(s), to massage and push excess fluid out of the limb towards the central body.

LIST OF REFERENCE NUMERALS

[0136] 1electroactive polymer (EAP) layer of softer durometer [0137] 2EAP layer of firmer durometer [0138] 3actuator including one or more EAP shape-morphing, sensing, and force attenuating layer [0139] 4small (pixel) conductive area [0140] 5conductive layer [0141] 6flexible coating (encapsulation) [0142] 7 surrounding flexible prosthetic liner [0143] 8encapsulated EAP shape-morphing, sensing, and force attenuating system [0144] 9 human residual limb [0145] 10flexible or bendable electrode(s) [0146] 11battery pack [0147] 12hard socket [0148] 13standard flexible prosthetic liner [0149] 14softer, more shape-morphing EAP zone [0150] 15open cell foam or firmer, less shape-morphing EAP zone [0151] 16EAP band [0152] 17opposite charged conductive electrode layer [0153] 18external hard component of compression boot [0154] 19fluid reservoir containing electrolyte [0155] 20first electrode [0156] 21second electrode

[0157] Electroactive Polymers

[0158] In some embodiments, the first electroactive ionic polymer is cross-linked with a first cross-linking polymeric chain. In certain specific embodiments, the first electroactive ionic polymer is an elastomeric polymer chain. Non-limiting examples of the elastomeric polymer chains include a poly(dimethylsiloxane) (PDMS) chain, and a poly(dimethylsiloxane) (PDMS) dimethacrylate chain. In certain specific embodiments, the first electroactive ionic polymer is cross-linked with a first cross-linking polymeric agent comprising a poly(dimethylsiloxane) (PDMS) dimethacrylate chain and a second crossing-linking polymeric agent different from the first cross-linking polymeric agent. In some embodiments, the first electroactive ionic polymer is cross-linked with a first cross-linking polymeric chain comprising a poly(dimethylsiloxane) (PDMS) dimethacrylate chain and a second crossing-linking polymeric agent different from the first cross-linking polymeric agent. As described herein, the first electroactive ionic polymer may be cross-linked with a first cross-linking polymeric chain and a second crossing-linking polymeric agent different from the first cross-linking polymeric agent. In certain embodiments, the first cross-linking polymer agent has elastic characteristics. Non-limiting examples of the first cross-linking polymer agent include a poly(dimethylsiloxane) (PDMS) dimethacrylate polymeric chain. In certain embodiments, the second cross-linking polymeric agent is selected from the group consisting of a poly(ethylene glycol) dimethacrylate chain, an ethylene glycol dimethacrylate, 1,1,1-trimethylolpropane, and a combination thereof. In certain embodiments, the first electroactive ionic polymeric material is selected from the group consisting of polymers of methacrylic acid, copolymers of methacrylic acid and methacrylic acetate salt, such as potassium or sodium salt, other ion-containing polymers or copolymers, and combinations thereof.

[0159] Therefore, in these embodiments, the electroactive polymer may be multimodal. In these embodiments, the first electroactive ionic polymer may comprise two or more cross-linking polymeric agents and thus have more than one desirable property. In certain specific embodiments, the property is one or more characteristics selected from the group consisting of resistance, elasticity, firmness, shape-morphing ability, resiliency and a combination thereof. Further use of third and/or fourth cross-linking polymer agents different from the first and second cross-lining polymer agents is contemplated. That is, the electroactive polymer may further comprise a fourth cross-linking polymer agent different from the first, second, and third cross-linking polymer agents.

[0160] In some embodiments, the first and/or second electroactive ionic polymers are described. The first and/or second electroactive ionic polymers can be polymers of one or more ion-containing monomers or generally any polymer containing one or more ionizable groups. In certain embodiments, the first and/or second electroactive ionic polymers comprise ion-containing monomers such as methacrylic acid, which can also contain polymers comprising non-ionic monomers such as 2-hydroxyethyl methacrylate, cross-linked with poly(ethylene glycol) dimethacrylate or other suitable cross-linking agents, such as ethylene glycol dimethacrylate, 1,1,1-trimethylolpropane trimethacrylate, or a combination of cross-linking agents. Other electroactive polymers may also be used as the electroactive material or as a component of the electroactive material, such as poly(vinyl alcohol), ionized poly(acrylamide), poly(acrylic acid), poly(acrylic acid)-co-(poly(acrylamide), poly(2-acrylamide-2-methyl-1-propane sulfonic acid), poly(methacrylic acid), poly(styrene sulfonic acid), quartemized poly(4-vinyl pyridinium chloride), poly(vinylbenzyltrimethyl ammonium chloride), sulfonated poly(styrene-b-ethylene-co-butylene-b-styrene), sulfonated poly(styrene), or materials that respond to electricity by movement, expansion, contraction, curling, bending, buckling, or rippling. The preferred electroactive material comprises the monomer methacrylic acid, polymerized and cross-linked, preferably with the cross-linking agent poly(ethylene glycol) dimethacrylate with a number average molecular weight around 330 grams per mole, cross-linked at a low level, less than 0.78 mole percent poly(ethylene glycol) dimethacrylate with respect to methacrylic acid, preferably cross-linked within a range of 0.31 to 0.44 mole percent poly(ethylene glycol) dimethacrylate with respect to methacrylic acid. In certain embodiments, prior to polymerization, the monomer and cross-linking agent is diluted with a solvent miscible or compatible with the ion-containing monomer(s). Once polymerized and cross-linked, the electroactive material may be further swollen with an electrolyte solution or electrolyte gel formulation. Other suitable materials and compositions for the electroactive material are described in U.S. Pat. Nos. 8,088,453, 7,935,743, and 5,736,590 and U.S. Ser. Nos. 13/843,959 and 14/476,646, the contents of which are expressly incorporated by reference.

[0161] In certain embodiments, different formulations, preferably with respect to cross-linking formulations containing electroactive polymers with different levels of cross-linking, can be used in different regions of the polymer in the prosthetic liner or other actuating or void-filling system to provide for different levels of softness, hardness, or shape-morphing as needed. In certain embodiments, multiple cross-linking strategies can be used to provide for multi-modality and impact resistance over a wide range of impact scenarios, and to be able to withstand repeated impacts from typical use.

[0162] In yet another aspect, an actuation device comprising one or more of the shape-morphing systems disclosed herein is described, wherein upon the application of an electrical potential to the first electrode, the first electroactive ionic polymer is configured to expand or contract to generate an actuation force to result in a movement of at least a portion of the actuation device from a first position to a second position.

[0163] In some embodiments, the electroactive polymer-based system also includes an electroconductivity-enhancing material in ionic communication with the first and/or electroactive ionic polymer. In some embodiments, the electroconductivity-enhancing material is selected from the group consisting of solvent, electrolyte solution, electrolyte gel formulation, carbon particles, conductive fibers, preceding weaves, preceding felts, preceding nano-particles, preceding nanotubes, metal ions, salt, and a combination thereof. In some embodiments, the electrolytes in the EAPs and EAP-based systems can be of the group comprising Group 1 ions and Group 7 ions, the group comprising Group 1 ions and sulfate or other anionic counter ions, the group comprising Group 2 ions and sulfate or other anionic counter ions, and combinations thereof. Non-Group 7 anions in the electrolyte solution component of the EAPs have the advantage of releasing oxygen gas when these EAPs are electrically activated and above the electrophoresis threshold of 1.23 V. Small amounts of oxygen expression in the prosthetic liner or hard socket can be therapeutic to the skin of residual limbs, and very therapeutic to the skin of the foot and/or leg being treated in the compression boot. Standard fuel cells require hydrogen and oxygen, releasing water and providing electricity. The EAPs and EAP-based systems in the instant invention operate best moist, so require water, and actuate with electric input.

[0164] In some embodiments, the electroactive polymer-based system further includes a power source. In some embodiments, the power source is a rechargeable or non-rechargeable battery pack. In some embodiments, above the electrophoresis threshold of 1.23 V, these EAPs may release hydrogen and oxygen. EAP actuation above the electrophoresis threshold of 1.23 V can allow for tie-in with a fuel cell(s), for energy efficient actuation of the EAPs and EAP-based systems in the instant invention.

[0165] In some embodiments, the electroactive polymer-based system is in a form selected from the group consisting of fibers, bulk, slabs, bundles, and combinations thereof.

FURTHER DESCRIPTION OF EMBODIMENT(S)

[0166] The EAPs and EAP-based systems in the instant invention are ideally suited for impact attenuation since these EAPs are neither a pure solid nor pure liquid. Due to the material's semi-solid composition and viscoelastic and damping properties, these EAPs and EAP-based systems exhibit non-Newtonian behavior. FIG. 14 illustrates drop tower data comparing EAPs in the instant invention (EAP samples in the instant invention are the RasFlex series) to traditional padding in Xenith and Riddell football helmets. Note the superior performance data of RasFlexSH18-22 from the high impact 4-foot impactor drops. From impact testing, in addition to the attenuation of impact force directly through the material (FIG. 14), the 20202.5 cm sample also propagated the force laterally with distinct wave-like behavior, which was observed using high-speed photography. The architecture of helmet padding using the EAPs and EAP-based systems in the instant invention can also come into play, where different layers or areas of the EAPs and EAP-based systems in the instant invention may be able to turn direct impact into glancing impact within the same EAP-based system (FIG. 1). Shaped and layered approaches, including anisotropy, potentially provide the EAPs and EAP-based systems with the ability to both attenuate the impact force through the padding and concurrently mitigate or spread the impact force laterally. Nano-level considerations in design and production of these EAPs and EAP-based systems can improve the speed of electro-actuation for potential shape-morphing in response to incoming impacts.

[0167] In an iterative design-test-redesign-retest cycle, EAP samples in the instant invention (RasFlex series in FIG. 14) of varying stiffness were developed, and exposed to drop tower impacts at approximately 2.5 or 4.2 m/s. The impactor consisted of a 5 kg carriage with cylindrical impact face that was dropped from a height onto a rigidly-held padding specimen. For comparison, the aforementioned test procedure was performed on football helmet padding from off-the-shelf helmets (Riddell and Xenith), which were selected because of their use by the NFL and because of their high ranking in helmet testing (Virginia Tech, http://www.beam.vt.edu/helmet/helmets_football.php). Note that the RasFlexSH18-22 EAP formulation provides impact attenuation that is comparable to the Riddell and Xenith padding at 2 foot drop (2.5 m/s), and provides better attenuation at drops from 4 feet (4.2 m/s). Drop testing was also conducted on samples previously frozen to 79 C. and then thawed to room temperature, on samples at 0 C., on samples at 40 C., and on samples heated to 100 C. and then returned to room temperature. No change in drop test performance or damage to material structure was found. An EAP RasFlex sample was also exposed to repeated low level impacts (1200 impacts at 908 N, 0.1s duration triangular wave, with 30 s wait time between impacts) and detected no damage to the material and no difference between pre- and post-drop testing at 2.4 and 4.5 m/s. In addition, the EAP and EAP systems in the instant invention operate well within the relative humidity range of 40% to 100%, and even uncoated, Ras Labs smart materials operate well in water, including the salinity of ocean water. For use as padding or liners, these EAPs and EAP-based systems are coated, such as with medical grade silicone.

[0168] The EAPs and EAP-based systems in the instant invention are variable resistors, and can sense mechanical pressure, from high impact (FIG. 14) to gentle pressure (FIG. 15). FIG. 15 shows the sensing abilities of these EAP and EAP-based systems under much gentler mechanical pressure than FIG. 14. The compression sensing of EAP Sample LA_12 was determined using an Instron Model 4466 Universal Testing Machine, at a speed of 3 mm/min with a peak compressive force of 174.964 N. Once the plates reached close to touching, the automatic stop provided an immediate release of pressure, which was also observed (FIG. 15). To track the pressure on the EAP, conductive layers were attached above and below the EAP, with wiring attached to an Arduino micro-processor, which was connected to a laptop computer for real-time analysis and data capture during the compression testing. For both prosthetic and robotics, what is missing is a convenient, streamlined system to provide sensory feedback, such a mechanical pressurewhat we know as touch. The EAPs and EAPs in the instant invention provide for shape-morphing, good sensing abilities (gentle touch to high impact), and force attenuation.

[0169] In addition to the shape-morphing, sensing, and force attenuation abilities, the EAPs and EAPs in the instant invention also provide for good creep resistance, good elasticity, and low hysteresis effects (FIG. 16). The creep resistance and hysteresis effects are magnitudes better than standard liner materials currently in the marketplace. This attribute in these EAP and EAP-based systems provide for very good elastic rebound of the material in the prosthetic liner (or as the prosthetic liner) and in pads for the hard socket, which will provide for improved comfort for the amputee, particularly during ambulation (walking and running).

[0170] This EAP-based thin film can be applied to many other applications, such as a sensing skin for pressure feedback (touch) on a robotic or prosthetic arm, for example. These EAPs and EAP-based systems in the instant invention could also be used as sensing pads, such as fingertips on a robotic or prosthetic hand, for example. Robotic hands are also known as grippers or end effectors. As a covering for a prosthetic or robotic arm or hand, in addition to sensing pressure, like skin, the covering could also be shape-morphing, with underlying areas attached to the linkages making the hand or arm, so in addition to sensing and looking life-like, the EAP-based covering could also assist with desired movement rather than being passive weight, thus act as muscles, alone or acting in combination (hybrid approach) with traditional prosthetic and robotic hands and arms.