Force sensing membrane

• US 20060137462A1
• Filed: 12/23/2004
• Published: 06/29/2006
• Est. Priority Date: 12/23/2004
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Scholz, Matthew T., Divigalpitiya, Ranjith, Patel, Vijay, Miholics, Gabriella, Kanno, David A., Chen, Pei-Jung
• Granted Patent: US 7,260,999 B2
• Time in Patent Office: Days
• US Class Current: 73/760
• CPC Class Codes: H01H 1/029 comprising conducting material dispersed in an elastic support or binding material

Abstract

A force sensing membrane comprises (a) a first conductor that is movable toward a second conductor; (b) a second conductor; and (c) a composite material disposed between the first and second conductors for electrically connecting the first and second conductors under application of sufficient pressure therebetween; and (d) means for measuring dynamic electrical response across the force sensing membrane, the composite material comprising conductive particles at least partially embedded in an elastomeric layer, the conductive particles having no relative orientation and being disposed so that substantially all electrical connections made between the first and second conductors are in the z direction, and the elastomeric layer being capable of returning to substantially its original dimensions on release of pressure.

Claims

1. A force sensing membrane comprising:

(a) a first conductor that is movable toward a second conductor;

(b) a second conductor;

(c) a composite material disposed between the first and second conductors for electrically connecting the first and second conductors under application of sufficient pressure therebetween;

and

(d) means for measuring dynamic electrical response across the force sensing membrane,

the composite material comprising conductive particles at least partially embedded in an elastomeric layer,

the conductive particles have no relative orientation and being disposed so that substantially all electrical connections made between the first and second conductors are in the z direction, and

the elastomeric layer being capable of returning to substantially its original dimensions on release of pressure.

2. The force sensing membrane of claim 1 wherein the elastomeric layer comprises an elastomeric material that has a substantially constant G′

between about 0°

C. and about 60°

C.

3. The force sensing membrane of claim 2 wherein the elastomeric layer comprises an elastomeric material that has a substantially constant G′

between about 0°

C. and about 60°

C.

4. The force sensing membrane of claim 1 wherein the elastomeric layer comprises an elasomeric material that has a G′

between about 1×

10³ Pa² and about 9×

10³ Pa² and a loss tangent between about 0.01 and about 0.06 at 1 Hz at 23°

C.

5. The force sensing membrane of claim 1 wherein the elastomeric layer comprises an elasomeric material that is self-healing.

6. The force sensing membrane of claim 1 wherein the elastomeric layer comprises an elastomeric material selected from the group consisting of silicones and styrenic block copolymers.

7. The force sensing membrane of claim 6 wherein the elastomeric layer comprises a silicone.

8. The force sensing membrane of claim 6 wherein the elastomeric layer comprises styrene-isoprene-styrene block copolymers or styrene-ethylene/butylene-styrene block copolymers.

9. The force sensing membrane of claim 1 wherein the conductive particles are disposed so that substantially all electrical connection made between the first and second conductors are through single particles.

10. The force sensing membrane of claim 9 wherein the conductive particles are disposed so that no more than two particles are in contact with each other.

11. The force sensing membrane of claim 10 wherein no two particles are in contact with each other.

12. The force sensing membrane of claim 1 wherein the conductive particles comprise a metal.

13. The force sensing membrane of claim 1 wherein the conductive particles comprise core particles having a conductive coating.

14. The force sensing membrane of claim 13 wherein the core particles comprise glass particles.

15. The force sensing membrane of claim 13 wherein the core particles comprise hollow particles

16. The force sensing membrane of claim 13 wherein the conductive coating comprises metal.

17. The force sensing membrane of claim 13 wherein the conductive coating comprises a conductive oxide.

18. The force sensing membrane of claim 1 wherein the conductive particles are substantially spherical.

19. The force sensing membrane of claim 1 wherein the conductive particles are fibers.

20. The force sensing membrane of claim 1 wherein the first and second conductors are disposed on first and second substrates respectively.

21. The force sensing membrane of claim 20 wherein at least one of the first and second substrates is flexible.

22. The force sensing membrane of claim 1 further comprising an overlay layer disposed on the first or second conductor.

23. The force sensing membrane of claim 1 wherein there is a gap between the composite material and one of the first and second conductors.

24. The force sensing membrane of claim 1 wherein the composite material further comprises non-conducting fillers.

25. The force sensing membrane of claim 1 wherein the thickness of the membrane is between about 1 mm about 500 mm.

26. The force sensing membrane of claim 25 wherein the thickness of the membrane is between about 1 mm and about 50 mm.

39. A device comprising the force sensing membrane of claim 1 incorporated into a sock, bandage, or insole.

41. A device comprising an array of a plurality of the force sensing membranes of claim 1.

45. A method of force sensing comprising applying pressure to the force sensing membrane of claim 1, and measuring the change in an electrical property across the force sensing membrane.

27. A force sensing membrane comprising:

(a) an elastomeric layer disposed on a first conductor; and

(b) a composite material comprising conductive particles at least partially embedded in an insulating material disposed on a second conductor;

at least one of the first and second conductors being movable toward the other conductor, the conductive particles electrically connecting the first and second conductors under application of sufficient pressure therebetween,

the conductive particles having no relative orientation and being disposed so that substantially all electrical connections made between the first and second conductors are in the z direction, and

the elastomeric layer being capable of returning to substantially its original dimensions on release of pressure.

28. The force sensing membrane of claim 27 wherein the insulating material is capable of returning to substantially its original dimensions on release of pressure.

29. The force sensing membrane of claim 27 wherein one or both of the elastomeric layer and the insulating material comprises an elastomeric material that has a substantially constant G′

between about 0°

C. and about 100°

C.

30. The force sensing membrane of claim 27 wherein one or both of the elastomeric layer and the insulating material comprises an elastomeric material that has a substantially constant G′

between about 0°

C. and about 60°

C.

31. The force sensing membrane of claim 27 wherein one or both of the elastomeric layer and the insulating material comprises an elastomeric material that has a G′

between about 1×

10³ Pa² and a loss tangent between about 0.01 and about 0.60 at 1 Hz at 23°

C.

32. The force sensing membrane of claim 27 wherein one or both of the elastomeric layer and the insulating material comprises an elastomeric material that is self-healing.

33. The force sensing membrane of claim 27 wherein the conductive particles are disposed so that substantially all electrical connections made between the first and second conductors are through single particles.

34. The force sensing membrane of claim 33 wherein the conductive particles are disposed so that no more than two particles are in contact with each other.

35. The force sensing membrane of claim 34 wherein no two particles are in contact with each other.

36. The force sensing membrane of claim 27 wherein the thickness of the composite layer is less than the average conductive particle size.

37. The force sensing membrane of claim 36 wherein at least some of the conductive particles are always in contact with the second conductor.

38. The force sensing membrane of claim 27 further comprising means for measuring dynamic electrical response across the force sensing membrane.

42. A device comprising the force sensing membrane of claim 27 incorporated into a sock, bandage, or insole.

44. A device comprising an array of a plurality of the force sensing membranes of claim 27.

46. A method of force sensing comprising:

(a) electrically connecting the first and second conductors of the force sensing membrane of claim 27 to a means for measuring dynamic electrical response, and

(b) measuring an electrical response across the force sensing membrane.

40. (canceled)

43. (canceled)