Multi-Layer Transparent Force Sensor

• US 20160062517A1
• Filed: 09/01/2015
• Published: 03/03/2016
• Est. Priority Date: 09/02/2014
• Status: Abandoned Application

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Pedder, James E., Zhong, John Z., Meyer, David J., Kang, Sunggu
• Application Number:
  US14/842,402
• Publication Number:
  US 20160062517A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 2203/04103 Manufacturing, i.e. details related to manufacturing processes specially suited for touch sensitive devices
• CPC Class Codes: G06F 3/04144 using an array of force sensing means position sensing using the local deformation of sensor cells G06F3/0447

Abstract

An optically transparent force sensor element includes multi-layer electrodes of two materials having different gauge factors to increase sensitivity of measured force magnitude. A passivation layer is positioned between the electrode layers in each element. One gauge factor may be positive while the other gauge factor may be negative.

Claims

1. An optically transparent force sensor adjacent to a force receiving surface comprising:

a substrate disposed below the force-receiving surface;

said substrate including a first and a second optically transparent electrode layer;

said first optically transparent electrode layer including a material having a different gauge factor from a gauge factor of a material comprising said second electrode layer; and

a passivation layer disposed between said first and second transparent electrode layers.

2. The force sensor of claim 1, wherein the first electrode layer material has a negative gauge factor and the second electrode layer material has a positive gauge factor.

3. The force sensor of claim 1, wherein the first transparent electrode layer material is indium-tin oxide.

4. The force sensor of claim 1, wherein the second transparent electrode layer material includes silver nanowire.

5. The force sensor of claim 1 further including a second substrate including:

a first and second optically transparent electrode layer;

said first electrode layer on said second substrate including a material having a different gauge factor from a gauge factor of material comprising said second electrode layer on said second substrate;

a passivation layer disposed between said transparent electrode layers; and

an adhesive layer between said second electrode layer of said second substrate and said second electrode layer of said first substrate.

6. The force sensor of claim 5, wherein the optically transparent first electrode layer on said second substrate has a negative gauge factor and said second optically transparent electrode layer on said second substrate has a positive gauge factor.

7. The force sensor of claim 5, wherein the first transparent electrode layer material on said second substrate includes indium-tin oxide.

8. The force sensor of claim 5, wherein the second transparent electrode layer material on said second substrate includes silver nanowire.

9. The force sensor of claim 6 wherein the adhesive layer comprises a thermally conductive and mechanically compliant material.

10. The force sensor of claim 6, wherein the adhesive layer comprises a pressure sensitive adhesive.

11. A method of manufacturing a force sensor comprising:

selecting a first substrate;

applying a first force-sensitive film to the first substrate;

applying a passivation layer to the first force-sensitive film; and

applying a second force-sensitive film to the passivation layer;

wherein the first force sensitive film and the second force sensitive film include materials with different gauge factors.

12. The force sensor of claim 11, wherein the first force sensitive film material has a negative gauge factor and the second force sensitive film layer material has a positive gauge factor.

13. The method of claim 11 further including:

selecting a second substrate;

applying a first force-sensitive film to the second substrate;

applying a passivation layer to the first force sensitive film on the second substrate;

applying a second force sensitive film to the passivation layer on the second substrate;

wherein the first force sensitive film on the second substrate and the second force sensitive film on the second substrate include materials with different gauge factors; and

bonding the first and second substrates with an adhesive layer;

wherein the adhesive layer comprises a thermally conductive and mechanically compliant material.

14. The method of claim 13, wherein the first and second force-sensitive films on the first and second substrates are made from at least one of the group consisting of an indium-tin oxide, carbon nanotubes, graphene, piezoresistive semiconductors, and piezoresistive metals.

15. The force sensor of claim 14, wherein the first force sensitive film material has a negative gauge factor and the second force sensitive film layer material has a positive gauge factor.

16. A method for detecting a magnitude of force applied to a portable electronic device comprising the steps of:

detecting a user touch on the electronic device;

measuring the electrical resistance difference between a first force sensor in first strain gauge layer and a first force sensor in a second strain gauge layer;

measuring the electrical resistance difference between a second force sensor in first strain gauge layer and a second force sensor in a second strain gauge layer;

calculating the magnitude of force applied by said user touch based upon said measured electrical resistance difference; and

sending said calculated force to said electronic device;

wherein said first force sensor and the second force sensor include materials with different gauge factors.

17. The method of claim 16 wherein the first force sensor has a negative gauge factor and the second force sensor has a positive gauge factor.

18. A method for detecting a magnitude of force applied to a portable electronic device comprising the steps of:

detecting a user touch on the electronic device;

measuring the electrical resistance change in a first force sensor;

measuring the electrical resistance change in a second force sensor;

calculating the magnitude of force applied by said user touch based upon said measured electrical resistance changes; and

sending said calculated force to said electronic device;

wherein said first force sensor and the second force sensor include materials with different gauge factors.

19. The method of claim 18 wherein the first force sensor includes a material with a negative gauge factor and the second force sensor includes a material with a positive gauge factor.

20. The method of claim 18 wherein the first and second force-sensor include at least one of the group consisting of an indium-tin oxide, carbon nanotubes, graphene, piezoresistive semiconductors, and piezoresistive materials.