Metallic nanoparticle pressure sensor

• US 8,669,952 B2
• Filed: 06/09/2011
• Issued: 03/11/2014
• Est. Priority Date: 06/09/2011
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Hashimura, Akinori, Tang, Liang, Voutsas, Apostolos T.
• Primary Examiner(s): Hicks, Charles V
• Application Number:
  US13/157,206
• Publication Number:
  US 20120313860A1
• Time in Patent Office: 1,006 Days
• Field of Search: 345/173
• US Class Current: 345/173
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• 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: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

An electrical pressure sensor is provided with a method for measuring pressure applied to a sensor surface. The method provides an electrical pressure sensor including a sealed chamber with a top surface, first electrode, second electrode, an elastic polymer medium, and metallic nanoparticles distributed in the elastic polymer medium. When the top surface of the sensor is deformed in response to an applied pressure, the elastic polymer medium is compressed. In response to decreasing the metallic nanoparticle-to-metallic nanoparticle mean distance between metallic nanoparticles, the electrical resistance is decreased between the first and second electrodes through the elastic polymer medium.

Claims

1. A method for measuring pressure applied to a sensor surface, the method comprising:

providing an electrical pressure sensor including a sealed chamber with a top surface, first electrode, second electrode, an elastic polymer medium, and metallic nanoparticles distributed in the elastic polymer medium;

deforming the top surface in response to an applied pressure;

compressing the elastic polymer medium;

decreasing a metallic nanoparticle-to-metallic nanoparticle mean distance; and

,

in response to decreasing the metallic nanoparticle-to-metallic nanoparticle mean distance, decreasing electrical resistance between the first and second electrodes through the elastic polymer medium.

2. The method of claim 1 wherein providing the electrical pressure sensor includes providing the electrical pressure sensor with the first electrode formed in the top surface and the second electrode formed on a bottom surface of the sealed chamber.

3. The method of claim 1 wherein providing the electrical pressure sensor includes providing the electrical pressure sensor with the first electrode formed in a first portion of a bottom surface of the sealed chamber and the second electrode formed in a second portion of the bottom surface, where the first portion is separated from the second portion.

4. The method of claim 1 wherein providing the electrical pressure sensor includes providing a metallic nanoparticle-to-metallic nanoparticle first mean distance of greater than 10 nanometers (nm), with no pressure applied to the top surface;

the method further comprising;

measuring a first electrical resistance between the first and second electrodes with no pressure applied to the pressure sensor top surface;

wherein deforming the top surface in response to the applied pressure includes deforming the top surface in response to a first applied pressure;

wherein decreasing the metallic nanoparticle-to-metallic nanoparticle mean distance includes decreasing the metallic nanoparticle-to-metallic nanoparticle mean distance to a second mean distance, less than 10 nm; and

,

wherein decreasing electrical resistance between the first and second electrodes through the elastic polymer medium includes decreasing to a second electrical resistance, less than the first electrical resistance.

5. The method of claim 4 wherein deforming the top surface in response to the applied pressure includes deforming the top surface in response to a second applied pressure, greater than the first applied pressure;

wherein decreasing the metallic nanoparticle-to-metallic nanoparticle mean distance includes decreasing the metallic nanoparticle-to-metallic nanoparticle mean distance to a third mean distance, less than the second mean distance; and

,

wherein decreasing electrical resistance between the first and second electrodes through the elastic polymer medium includes decreasing to a third electrical resistance, less than the second electrical resistance.

6. The method of claim 5 wherein decreasing electrical resistance between the first and second electrodes to the second electrical resistance includes the second electrical resistance decreasing as a result of electric field assisted tunneling between adjacent metallic nanoparticles.

7. The method of claim 6 wherein decreasing electrical resistance between the first and second electrodes to the third electrical resistance includes the third electrical resistance being a result of microscopic contacts between adjacent metallic nanoparticles.

8. The method of claim 6 decreasing the second electrical resistance as a result of electric field assisted tunneling includes creating a current as follows:

9. The method of claim 5 wherein providing the electrical pressure sensor with the metallic nanoparticle-to-metallic nanoparticle first mean distance includes providing a metallic nanoparticle fill volume of less than about 20% in the elastic polymer medium.

10. The method of claim 9 wherein decreasing the metallic nanoparticle-to-metallic nanoparticle mean distance to the third mean distance includes creating a fill volume percentage of greater than about 25%.

11. The method of claim 1 wherein providing the electrical pressure sensor including providing a polymer network liquid crystal (PNLC) medium and Ag metallic nanoparticles separated by a mean distance of greater than 10 nm, when no pressure is applied to the pressure sensor top surface.

12. A pressure sensor comprising:

a sealed chamber with a top surface;

a first electrode;

a second electrode;

an elastic polymer medium, with distributed metallic nanoparticles, at least partially filling the sealed chamber and in contact with the first and second electrodes when the top surface is deformed by an applied pressure.

13. The pressure sensor of claim 12 wherein the metallic nanoparticles have a metallic nanoparticle-to-metallic nanoparticle mean distance that decreases in response to applied pressure on the top surface, resulting in decreased electrical resistance between the first and second electrodes through the elastic polymer medium.

14. The pressure sensor of claim 12 wherein the sealed chamber has a bottom surface;

wherein the first electrode is formed in the top surface; and

,

wherein the second electrode is formed on the bottom surface of the sealed chamber.

15. The pressure sensor of claim 12 wherein the sealed chamber has a bottom surface;

wherein the first electrode is formed on a first portion of the bottom surface of the sealed chamber; and

,

wherein the second electrode is formed on a second portion of the bottom surface of the sealed chamber, and is physically separated from the first electrode.

16. The pressure sensor of claim 12 wherein the metallic nanoparticles have a metallic nanoparticle-to-metallic nanoparticle first mean distance of greater than 10 nanometers (nm), with no pressure applied to the top surface.

17. The pressure senor of claim 12 wherein the metallic nanoparticles have a fill volume of less than about 20% in the elastic polymer medium, with no pressure applied to the top surface, and a fill volume percentage of greater than about 25%, with pressure applied to the top surface.

18. The pressure sensor of claim 12 wherein the elastic polymer medium is polymer network liquid crystal (PNLC) medium and the metallic nanoparticles are Ag.

19. The pressure sensor of claim 12 wherein the metallic nanoparticles conduct an electric field assisted tunneling between the first and second electrodes when the top surface is deformed by applied pressure, as follows:

20. An electronic display with an overlying touchscreen, the display comprising:

a front panel with an array of display pixels arranged in a plurality of adjacent sequences;

a backlight panel light source underlying the front panel;

a touchscreen overlying the front panel with an array of pressure sensor cells arranged in a plurality of adjacent sequences, each pressure senor cell including;

a sealed chamber with a top surface;

a transparent first electrode;

a transparent second electrode;

a transparent elastic polymer medium, with distributed metallic nanoparticles, at least partially filling the sealed chamber and in contact with the first and second electrodes when the top surface is deformed by an applied pressure.