DUAL LAYER FORCE SENSITIVE RESISTOR SENSOR

• US 20170153738A1
• Filed: 11/30/2016
• Published: 06/01/2017
• Est. Priority Date: 11/30/2015
• Status: Abandoned Application

• Current Assignee: Flextronics America LLC (Flextronics International Limited)
• Original Assignee: Flex, Ltd.
• Inventors: Ma, Jiayin, Deva, Shaily
• Application Number:
  US15/365,203
• Publication Number:
  US 20170153738A1
• Time in Patent Office: Days
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G01L 1/20 by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids of piezo-resistive materials G01L1/18; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
• CPC Class Codes: G01L 1/205 using distributed sensing elements

Abstract

According to one embodiment, a multi-layer force sensor can comprise two or more Force Sensitive Resistors (FSRs), Force Sensitive Capacitors (FSCs), or other force sensitive devices. Each of these force sensitive devices can comprise a different layer of the multi-layer force sensor. Additionally, each of these different layers can be constructed of a different material providing different responses, i.e., different resistance, conductance, etc., over the same range of pressure or force. As a force is applied to the multi-layer sensor, this difference in response to the force between the layers can be used to determine a value for the force. The multi-layer force sensor can be implemented in a bridge circuit. The bridge circuit can be used to measure the differences in resistance, conductance, etc. between the different layers of the multi-layer sensor.

Claims

1. A multi-layer force sensor comprising:

a first force sensitive layer of a first force sensitive material; and

a second force sensitive layer of a second force sensitive material, wherein a response of a characteristic of the first force sensitive material for a range of force applied to the multi-layer force sensor is different from a response of the same characteristic of the second force sensitive material for the same range of force applied to the multi-layer force sensor and wherein a difference between the response of the first force sensitive material and the response of the second force sensitive material indicates an amount of force applied to the multi-layer force sensor.

2. The multi-layer force sensor of claim 1, further comprising an intermediate layer between the first force sensitive layer and the second force sensitive layer.

3. The multi-layer force sensor of claim 1, further comprising one or more conductive leads electrically connected with each or the first force sensitive layer and the second force sensitive layer.

4. The multi-layer force sensor of claim 1, wherein the first force sensitive layer comprises a first Force Sensitive Resistor (FSR), wherein the second force sensitive layer comprises a second FSR, and wherein the characteristic comprises resistance of the first force sensitive material and the second force sensitive material.

5. The multi-layer force sensor of claim 4, wherein the first force sensitive material and the second force sensitive material comprise a conductive elastomer, a conductive foam, or a conductive ink.

6. The multi-layer force sensor of claim 1, wherein the first force sensitive layer comprises a first Force Sensitive Capacitor (FSC), wherein the second force sensitive layer comprises a second FSC, and wherein the characteristic comprises capacitance of the first force sensitive material and the second force sensitive material.

7. A bridge circuit comprising:

a first force sensitive layer of a multi-layer force sensor and comprising a first force sensitive material;

a second force sensitive layer of the multi-layer force sensor, the second force sensitive layer electrically connected with the first force sensitive layer at a first intermediate point of the bridge circuit and comprising a second force sensitive material, wherein a response of a characteristic of the first force sensitive material for a range of force applied to the multi-layer force sensor is different from a response of the same characteristic of the second force sensitive material for the same range of force applied to the multi-layer force sensor;

a first bridge resistor electrically connected with the first force sensitive layer of the multi-layer sensor at a second intermediate point of the bridge circuit; and

a second bridge resistor electrically connected with the first bridge resistor at a third intermediate point of the bridge circuit and the second force sensitive layer of the multi-layer force sensor at a fourth intermediate point of the bridge circuit, wherein a difference between the response of the first force sensitive material and the response of the second force sensitive material measured between the second intermediate point of the bridge circuit and fourth intermediate point of the bridge circuit indicates an amount of force applied to the multi-layer force sensor.

8. The bridge circuit of claim 7, further comprising an intermediate layer between the first force sensitive layer and the second force sensitive layer.

9. The bridge circuit of claim 7, wherein the first force sensitive layer comprises a first Force Sensitive Resistor (FSR), wherein the second force sensitive layer comprises a second FSR, and wherein the characteristic comprises resistance of the first force sensitive material and the second force sensitive material.

10. The bridge circuit of claim 9, wherein the first force sensitive material and the second force sensitive material comprise a conductive elastomer, a conductive foam, or a conductive ink.

11. The bridge circuit of claim 7, wherein the first force sensitive layer comprises a first Force Sensitive Capacitor (FSC), wherein the second force sensitive layer comprises a second FSC, and wherein the characteristic comprises capacitance of the first force sensitive material and the second force sensitive material.

12. A method for measuring force using a multi-layer force sensor, the method comprising:

receiving a force applied to the multi-layer force sensor, the multi-layer force sensor comprising a first force sensitive layer of a first force sensitive material and a second force sensitive layer of a second force sensitive material, wherein a response of a characteristic of the first force sensitive material for a range of force applied to the multi-layer force sensor is different from a response of the same characteristic of the second force sensitive material for the same range of force applied to the multi-layer force sensor;

detecting a difference between the response of the first force sensitive material and the response of the second force sensitive material; and

determining a value for a amount of force applied to the multi-layer force sensor based on the detected difference between the response of the first force sensitive material and the response of the second force sensitive material.

13. The method of claim 12, wherein the multi-layer force sensor further comprises a bridge circuit, wherein the second force sensitive layer is electrically connected with the first force sensitive layer at a first intermediate point of the bridge circuit, wherein a first bridge resistor is electrically connected with the first force sensitive layer of the multi-layer sensor at a second intermediate point of the bridge circuit, wherein a second bridge resistor electrically connected with the first bridge resistor at a third intermediate point of the bridge circuit and the second force sensitive layer of the multi-layer force sensor at a fourth intermediate point of the bridge circuit, and wherein the difference between the response of the first force sensitive material and the response of the second force sensitive material is detected between the second intermediate point of the bridge circuit and fourth intermediate point of the bridge circuit.

14. The method of claim 12, wherein the first force sensitive layer comprises a first Force Sensitive Resistor (FSR), wherein the second force sensitive layer comprises a second FSR, and wherein the characteristic comprises resistance of the first force sensitive material and the second force sensitive material.

15. The method of claim 14, wherein the first force sensitive material and the second force sensitive material comprise a conductive elastomer, a conductive foam, or a conductive ink.

16. The method of claim 12, wherein the first force sensitive layer comprises a first Force Sensitive Capacitor (FSC), wherein the second force sensitive layer comprises a second FSC, and wherein the characteristic comprises capacitance of the first force sensitive material and the second force sensitive material.