Conducting polymer actuator

• US 6,249,076 B1
• Filed: 04/14/1999
• Issued: 06/19/2001
• Est. Priority Date: 04/14/1998
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Madden, John D., Kanigan, Tanya S., Lafontaine, Serge, Hunter, Ian W.
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US09/292,041
• Time in Patent Office: 797 Days
• Field of Search: 310/363, 310/364, 310/365, 310/800
• US Class Current: 310/363
• CPC Class Codes: A61B 2017/00871 polymeric
• CPC Class Codes: F03G 7/005 Electro-chemical actuators; Actuators having a material for absorbing or desorbing gas, e.g. a metal hydride; Actuators using the difference in osmotic pressure between fluids; Actuators with elements stretchable when contacted with liquid rich in ions, with UV light, with a salt solution
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

Abstract

Embodiments of actuators having an active member including a polymer having a surface, an electrolyte coupled to the surface, and an electrolyte are provided. Actuators which, when an electrical potential is applied across the electrolyte between the active member and the counter electrode, exert force per unit area of at least 10 MPa are described. Particular designs utilizing stretch aligned conducting polymers as active members are discussed.

Claims

1. An actuator comprising:

an electrolyte;

a counter electrode coupled to the electrolyte; and

an active member comprising a polymer, the active member having an axis, a length defined along the axis, and having a surface coupled to the electrolyte, the active member capable of exerting, essentially along the axis, a force per unit area of at least 10 MPa concurrent with application of an electrical potential between the active member and the counter electrode.

2. An actuator according to claim 1, further comprising:

a flexible skin for separating the electrolyte from an ambient environment.

3. An actuator according to claim 1, wherein the polymer is selected from conducting polymers and non-conducting polymers, the non-conducting polymers having associated interpenetrating conducting networks.

4. An actuator according to claim 1, wherein the electrolyte is a liquid.

5. An actuator according to claim 4, wherein the liquid is propylene carbonate.

6. An actuator according to claim 5, wherein a salt is added to the propylene carbonate, the salt being tetraethylammonium hexafluorophosphate.

7. An actuator according to claim 3, wherein the polymer is a conducting polymer.

8. An actuator according to claim 7, wherein the active member is a film.

9. An actuator according to claim 7, wherein the active member is a fiber.

10. An actuator according to claim 7, wherein the active member is a set of substantially parallel fibers.

11. An actuator according to claim 10, wherein the application of the electrical potential activates at least one of the set of fibers.

12. An actuator according to claim 7, wherein the conducting polymer is polypyrrole.

13. An actuator according to claim 12, wherein the electrolyte is a gel.

14. An actuator according to claim 13, wherein the gel includes agar.

15. An actuator according to claim 14, the electrolyte having an electrolyte volume and the active member having a member volume, wherein the electrolyte volume is equal to at least five times the member volume.

16. An actuator according to claim 15, wherein the counter electrode is distributed substantially over the length of the active member and comprises a coiled metal wire.

17. An actuator according to claim 7, wherein the counter electrode is distributed substantially over the length of the active member and comprises a conducting polymer.

18. An actuator according to claim 17, wherein the counter electrode is a second active member, the electrical potential applied between the active members across the electrolyte.

19. An actuator according to claim 18, further comprising:

a drive arrangement;

so that the application of the electrical potential causes the active member and the second active member to exert forces in opposite directions essentially along the axis, resulting in torque being applied to the drive arrangement.

20. An actuator according to claim 1, wherein the electrolyte is a gel.

21. An actuator according to claim 1, wherein the counter electrode is distributed substantially over the length of the active member and comprises a coiled metal wire.

22. An actuator according to claim 1, wherein the counter electrode is distributed substantially over the length of the active member and comprises a metallic thin film.

23. An actuator according to claim 22, wherein the metallic thin film contains a metal selected from gold, palladium, platinum and combinations thereof.

24. An actuator comprising:

an electrically deformable, conducting polymer active member having a surface, a member volume, a length and an axis;

an electrolyte, having an electrolyte volume, coupled to the surface of the active member;

a counter electrode coupled to the electrolyte; and

a housing, including side walls, having an interior surface;

so that the active member, the electrolyte and the counter electrode are located substantially within the housing, the active member spatially displaced from the interior surface, and so that application of an electrical potential between the active member and the counter electrode causes the active member to deform essentially along the axis without exerting force on the walls.

25. An actuator according to claim 24, wherein the active member is a film.

26. An actuator according to claim 24, wherein the active member is a fiber.

27. An actuator according to claim 24, wherein the active member is a set of substantially parallel fibers.

28. An actuator according to claim 27, wherein the application of the electrical potential causes at least one of the set of fibers to deform.

29. An actuator according to claim 24, wherein the conducting polymer is polypyrrole.

30. An actuator according to claim 29, wherein the electrolyte is a gel.

31. An actuator according to claim 30, wherein the gel includes agar.

32. An actuator according to claim 31, wherein the electrolyte volume is equal to at least five times the member volume.

33. An actuator according to claim 32, wherein the counter electrode is distributed substantially over the length of the active member and is a coiled metal wire.

34. An actuator according to claim 24, wherein the electrolyte is a gel.

35. An actuator according to claim 24, wherein the counter electrode is distributed substantially over the length of the active member and is a coiled metal wire.

36. An actuator according to claim 24, wherein the counter electrode is distributed substantially over the length of the active member and is a conducting polymer.

37. An actuator according to claim 36, wherein the counter electrode is a second active member, the electrical potential applied between the active members across the electrolyte.

38. An actuator according to claim 37, further comprising:

a drive arrangement;

so that the application of the electrical potential causes the active member and the second active member to exert forces in opposite directions essentially along the axis, resulting in torque being applied to the drive arrangement.

39. An actuator according to claim 24, wherein the counter electrode is distributed substantially over the length of the active member and is a metallic thin film.

40. An actuator according to claim 39, wherein the metallic thin film contains a metal selected from gold, palladium, platinum and combinations thereof.

41. An actuator according to claim 24, wherein the housing is made from polyethylene.

42. An actuator according to claim 41, the housing having a wall thickness, wherein the thickness is no more than 20% of an actuator dimension, the actuator dimension and the wall thickness measured along a common axis normal to the axis of the active member.

43. An actuator comprising:

an active member having a surface, a member volume, a length, and an axis, the active member including a polymer and including a plurality of electrically conductive attachment areas, the areas spaced at locations along the length;

an electrolyte, having an electrolyte volume, coupled to the surface of the active member;

and a counter electrode coupled to the electrolyte;

so that application of an electrical potential between the counter electrode and an area causes the active member to deform essentially along the axis.