Interdigital force switches and sensors

• US 20070022828A1
• Filed: 07/29/2005
• Published: 02/01/2007
• Est. Priority Date: 07/29/2005
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Divigalpitiya, Ranjith, Chen, Pei-Jung
• Granted Patent: US 7,509,881 B2
• Time in Patent Office: Days
• US Class Current: 73/862.41
• CPC Class Codes: H01H 1/029 comprising conducting material dispersed in an elastic support or binding material
• CPC Class Codes: H01H 2239/078 Variable resistance by variable contact area or point

Abstract

An interdigital electronic device comprises a conductor, an interdigital electrode, and a composite material disposed between the conductor and the interdigital electrode for electrically connecting the conductor and the interdigital electrode under application of sufficient pressure therebetween. The composite material comprises conductive particles at least partially embedded in an electrically insulating layer. The conductive particles have no relative orientation and are disposed so that substantially all electrical connections made between the conductor and the interdigital electrode are in the z direction. At least one of the conductor and the interdigital electrode is movable toward the other.

Claims

1. An interdigital electronic device comprising:

(a) a conductor;

(b) an interdigital electrode; and

(c) a composite material disposed between the conductor and the interdigital electrode for electrically connecting the conductor and the interdigital electrode under application of sufficient pressure therebetween,

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

the conductive particles having no relative orientation and being disposed so that substantially all electrical connections made between the conductor and the interdigital electrode are in the z direction,

wherein at least one of the conductor and the interdigital electrode is movable toward the other.

2. The interdigital electronic device of claim 1 wherein the conductive particles are disposed so that substantially all electrical connections made between the conductor and the interdigital electrode are through single particles

3. The interdigital electronic device of claim 2 wherein the conductive particles are disposed so that no more than two particles are in contact with each other.

4. The interdigital electronic device of claim 3 wherein no two particles are in contact with each other.

5. The interdigital electronic device of claim 1 wherein the conductor comprises a metallic coating provided on a plastic film.

6. The interdigital electronic device of claim 5 wherein the metallic coating and plastic film are transparent.

7. The interdigital electronic device of claim 1 wherein the conductor comprises an interdigital electrode.

8. The interdigital electronic device of claim 1 wherein the interdigital electrode is disposed on a substrate.

9. The interdigital electronic device of claim 8 wherein the substrate is flexible.

10. The interdigital electronic device of claim 8 wherein the substrate is transparent.

11. The interdigital electronic device of claim 1 wherein the conductor and the interdigital electrode are transparent.

12. The interdigital electronic device of claim 11 wherein at least one of the conductor and the interdigital electrode comprises a transparent conductive oxide.

13. The interdigital electronic device of claim 1 further comprising means for measuring electrical response across the device.

14. The interdigital electronic device of claim 1 wherein the electrically insulating layer is capable of returning to substantially its original dimensions on the release of pressure.

15. The interdigital electronic device of claim 14 wherein the electrically insulating layer comprises an elastomeric material that has a substantially constant G′

between about 0°

C. and about 100°

C.

16. The interdigital electronic device of claim 15 wherein the electrically insulating layer comprises an elastomeric material that has a substantially constant G′

between about 0°

C. and about 60°

C.

17. The interdigital electronic device of claim 14 wherein the electrically insulating layer comprises an elastomeric material that has a G′

between about 1×

10³ Pa and about 9×

10⁵ Pa and a loss tangent between about 0.01 and about 0.60 at 1 Hz at 23°

C.

18. The interdigital electronic device of claim 14 wherein the electrically insulating layer comprises an elastomeric material that is self-healing.

19. The interdigital electronic device of claim 14 further comprising means for measuring dynamic electrical response across the device.

20. The interdigital electronic device of claim 1 wherein the device is a force activated switch or a force sensor.