Rolled electroactive polymers

• US 20040217671A1
• Filed: 03/03/2004
• Published: 11/04/2004
• Est. Priority Date: 05/22/2001
• Status: Active Grant

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Bonwit, Neville A., Pei, Qibing, Rosenthal, Marcus A.
• Granted Patent: US 7,233,097 B2
• Time in Patent Office: Days
• US Class Current: 310/328
• CPC Class Codes: A61M 2205/0283 Electro-active polymers [EAP]
• CPC Class Codes: A61M 5/142 Pressure infusion, e.g. using pumps
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: F01L 1/46 Component parts, details, or accessories, not provided for in preceding subgroups
• CPC Class Codes: F01L 2301/00 Using particular materials
• CPC Class Codes: F01L 7/02 with cylindrical, sleeve, or part-annularly shaped valves of disc type F01L7/06; of conical type F01L7/08
• CPC Class Codes: F01L 9/20 by electric means
• CPC Class Codes: F04B 35/00 Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
• CPC Class Codes: F04B 43/043 Micropumps
• CPC Class Codes: H02N 11/006 Motors
• CPC Class Codes: H04R 19/00 Electrostatic transducers
• CPC Class Codes: H04R 2307/029 Diaphragms comprising fibres
• CPC Class Codes: H10N 30/05 Manufacture of multilayered piezoelectric or electrostrictive devices, or parts thereof, e.g. by stacking piezoelectric bodies and electrodes
• CPC Class Codes: H10N 30/098 Forming organic materials
• CPC Class Codes: H10N 30/2046 adapted for multi-directional bending displacement
• CPC Class Codes: H10N 30/206 using only longitudinal or thickness displacement, e.g. d33 or d31 type devices
• CPC Class Codes: H10N 30/302 Sensors
• CPC Class Codes: H10N 30/506 of cylindrical shape with stacking in radial direction, e.g. coaxial or spiral type rolls
• CPC Class Codes: H10N 30/802 Drive or control circuitry or methods for piezoelectric or electrostrictive devices not otherwise provided for
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF
• CPC Class Codes: Y10T 29/42 : Piezoelectric device making
• CPC Class Codes: Y10T 29/43 : Electric condenser making
• CPC Class Codes: Y10T 29/49117 : Conductor or circuit manufacturing
• CPC Class Codes: Y10T 29/49124 : On flat or curved insulated base, e.g., printed circuit, etc.
• CPC Class Codes: Y10T 29/49128 : Assembling formed circuit to base
• CPC Class Codes: Y10T 29/49139 : by inserting component lead or terminal into base aperture
• CPC Class Codes: Y10T 29/49155 : Manufacturing circuit on or in base

Abstract

The invention describes rolled electroactive polymer devices. The invention also describes employment of these devices in a wide array of applications and methods for their fabrication. A rolled electroactive polymer device converts between electrical and mechanical energy; and includes a rolled electroactive polymer and at least two electrodes to provide the mechanical/electrical energy conversion. Prestrain is typically applied to the polymer. In one embodiment, a rolled electroactive polymer device employs a mechanism, such as a spring, that provides a force to prestrain the polymer. Since prestrain improves mechanical/electrical energy conversion for many electroactive polymers, the mechanism thus improves performance of the rolled electroactive polymer device.

Claims

1. A device for converting between electrical and mechanical energy, the device comprising:

a polymer roll transducer comprising a) an electroactive polymer including at least one active area and b) at least two electrodes in electrical communication with the active area wherein at least a portion of the electroactive polymer is wrapped upon itself to form a roll;

at least one support member coupled to the polymer roll transducer for providing at least one of i) a force that strains at least a portion of the polymer, ii) a force for controlling bending in the polymer roll transducer and iii) combinations thereof; and

at least one mechanical linkage coupled to the polymer roll transducer for allowing a force or a moment generated in a first portion of the electroactive polymer to be communicated to a second portion of the electroactive polymer.

2. The device of claim 1, further comprising:

an end cap coupled to the support member in a manner allowing movement of the end cap in one or more directions.

3. The device of claim 2, wherein the end cap is rotationally coupled to the support member.

4. The device of claim 2, wherein an actuation of the active area of the electroactive polymer provides a force to moves the end cap in the one or more directions.

5. The device of claim 2, wherein a non-active area of the electroactive polymer provides a force to the move the end cap in the one or more directions.

6. The device of claim 2, wherein the electroactive polymer is attached to the end cap.

7. The device of claim 6 wherein the electroactive polymer is attached to the end cap via at least one of an adhesive, a pin, a fastener, a cap or combinations thereof.

8. The device of claim 2 wherein the end cap is operable to act as the mechanical linkage.

9. The device of claim 2 further comprising a sensor for determining a position of the end cap.

10. The device of claim 1 further comprising a logic device for controlling the actuation of the polymer roll transducer.

11. The device of claim 1 further comprising a base rigidly coupled to the support member.

12. The device of claim 11 wherein the electroactive polymer is attached to the base.

13. The device of claim 11 wherein a plurality of mechanical linkages are rotationally coupled to a support member.

14. The device of claim 13 wherein the mechanical linkages and the support member are disposed within a hollow portion of the roll.

15. The device of claim 13 wherein the mechanical linkages are disk shaped.

16. The device of claim 13 wherein tensile forces, stored in a number of portions of the electroactive polymer, are transferred via the plurality of mechanical linkages to other portions of the electroactive polymer.

17. The device of claim 16, the transferred tensile forces reduce an energy required to actuate the active area of area of the electroactive polymer

18. The device of claim 1 wherein the electroactive polymer is attached to at least one of the support member, the mechanical linkage or combinations thereof.

19. The device of claim 1 wherein at least one of the support member, the mechanical linkage or combinations thereof are arranged in a manner to maintain a shape of the roll.

20. The device of claim 1 further comprising at least one sensor coupled to the device.

21. The device of claim 20 wherein the sensor is arranged for measuring or determining one or more of an angular position, an angular velocity or an angular position of more components of the device.

22. The device of claim 20 wherein the sensor is for measuring a strain of a component in the device.

23. The device of claim 1 wherein the roll is cut in one or more places for limiting a propagation of a force or a moment from a first portion of the roll to a second portion of the roll.

24. The device of claim 23, wherein the one or more cuts are for creating one or more muscle strands.

25. The device of claim 24, further comprising a plurality of muscle strands of varying lengths.

26. The device of claim 24, wherein the muscle strands are attached to the device at one or more points along their length.

27. The device of claim 26, wherein a first muscle strand is stretched or compressed prior to its attachment to the device to increase or decrease an initial strain in a portion of the muscle strand.

28. The device of claim 1, wherein the device includes a joint for coupling a first component of the device to a second component of the device and for allowing a relative rotation between the two components.

29. The device of claim 28, wherein the first component is a first support member and the second component is a second support member.

30. The device of claim 28, wherein the first component is the support member and the second component is the mechanical linkage.

31. The device of claim 1 wherein the mechanical linkage is a spring.

32. The device of claim 1 the support member comprises a first component rotationally coupled to a second component and the transducer is arranged in a manner to move the first component and the second component to different angular position relative to one another.

33. The device of claim 1 wherein the electroactive polymer is attached at one or more points to create moment arms of varying lengths about a rotational coupling point in the device wherein each moment arm is a distance between a force generated in the electroactive polymer and the rotational coupling point.

34. The device of claim 1, wherein at least a portion of the support member or the mechanical linkage is disposed in a hollow central part of the roll.

35. The device of claim 1 wherein at least one of the support member or the mechanical linkage provides anisotropic prestrain on the electroactive polymer.

36. The device of claim 1 wherein at least one of the support member or the mechanical linkage provides prestrain in an axial direction on the rolled electroactive polymer.

37. The device of claim 1 wherein at least one of the support member or the mechanical linkage provides prestrain in a circumferential direction on the rolled electroactive polymer.

38. The device of claim 1 wherein at least one of the support member or the mechanical linkage provides tensile prestrain on the polymer.

39. The device of claim 1 wherein the electroactive polymer is a dielectric elastomer.

40. The device of claim 1 wherein the electroactive polymer has an elastic modulus at most about 100 MPa.

41. The device of claim 1, wherein the support member comprises of plurality of telescoping tubes.

42. The device of claim 1 wherein the electroactive polymer is attached to the support member or the mechanical linkage via at least one of an adhesive, a pin, a fastener, a cap or combinations thereof.

43. The device of claim 42 wherein the adhesive, the pin, the fastener or the cap is electrically conductive and provide electrical communication to the active area.

44. The device of claim 1 wherein the device is part of a biomemetic robot.

45. The device of claim 1 wherein the device is part of a sensor.

46. The device of claim 45 wherein the sensor is for detecting at least one of an angular position, a linear position, an angular velocity, a linear velocity, an angular acceleration, a linear acceleration or combinations thereof.

47. The device of claim 1 wherein the device is arranged to receive at least one of a force, a moment or combinations thereof generated outside of the device via at least one of the support member and the mechanical linkage.

48. The device of claim 45 wherein the device is arranged to generate a feed back force, a feed back moment or combinations thereof in response to the received force or the received moment.

49. The device of claim 1 wherein the device is a part of a joystick.

50. The device of claim wherein the device is part of an automobile.

51. A method for fabricating an electroactive polymer device, the method comprising:

disposing at least two electrodes on an electroactive polymer;

rolling the electroactive polymer about at least one of a support member, a mechanical linkage, an end cap, a base or combinations thereof to produce an electroactive polymer roll; and

securing the electroactive polymer roll to maintain its rolled configuration.

52. The method of claim 51 wherein the electroactive polymer is rolled about the support member coupled to the mechanical linkage.

53. The method of claim 51 wherein the electroactive polymer is rolled about the end cap rotationally coupled to the support member and the support member rigidly coupled to the base.

54. The method of claim 51 wherein the electroactive polymer is secured to at least one of the support member, the mechanical linkage, the end cap, the base or combinations thereof.

55. The method of claim 54 wherein the polymer roll is secured using at least one of adhesive, a fastener, a pin, a cap or combinations thereof.

56. The method of claim 51, wherein one or more portions of the electroactive polymer is secured in tension.

57. The method of claim 51 wherein the mechanical linkage is for allowing a force or moment generated in a first portion of the electroactive polymer to be communicated to a second portion of the electroactive polymer

58. The method of claim 51 wherein the support member is for providing at least one of i) a force that strains at least a portion of the electroactive polymer roll, ii) a force for controlling bending in the electroactive polymer roll and iii) combinations thereof.

59. The method of claim 51 further comprising cutting the electroactive polymer roll at one or more locations to limit a propagation of a force or a moment from a first portion of the electroactive polymer roll to a second portion of the electroactive polymer roll.

60. The method of claim 59 wherein the electroactive polymer roll is cut into a plurality of muscle strands.

61. The method of claim 60 wherein the muscle strands are of varying lengths.

62. The method of claim 60 wherein the muscle strands are secured at three or more points.

63. The device of claim 60 further comprising securing end points of a first muscle strand, stretching or compressing the first muscle strand about an attachment point between the end points to alter a strain in a portion of the first muscle strand and securing the attachment point.

64. The method of claim 51 wherein the electroactive polymer is a dielectric elastomer.

65. A device for converting between electrical and mechanical energy, the device comprising:

a polymer roll transducer comprising a) an electroactive polymer including at least one active area wherein the active area is arranged to deform in response to an electric field and b) at least two electrodes in electrical communication with the active area wherein at least a portion of the electroactive polymer is wrapped upon itself to form a roll;

at least one support member coupled to the polymer roll transducer for providing at least one of i) a force that strains at least a portion of the polymer, ii) a force for controlling bending in the polymer roll transducer and iii) combinations thereof; and

a plurality of mechanical linkages coupled to the support member and coupled to the polymer roll transducer for allowing a force or a moment generated in a first portion of the electroactive polymer to be communicated to a second portion of the electroactive polymer.

66. The device of claim 65, wherein the mechanical linkages are rotationally coupled to the support member.

67. The device of claim 65, wherein the mechanical linkages are disc-shaped.