Transparent force sensor and method of fabrication

• US 9,018,030 B2
• Filed: 03/17/2010
• Issued: 04/28/2015
• Est. Priority Date: 03/20/2008
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Li, Hao, Maniar, Papu, Wei, Yi
• Primary Examiner(s): Rizkallah, Kimberly
• Assistant Examiner(s): Ligai, Maria
• Application Number:
  US12/725,699
• Publication Number:
  US 20110227836A1
• Time in Patent Office: 1,868 Days
• Field of Search: 438/50, 438/51, 438/53, 257/415, 257/417, 257/E29.324, 345/173, 345/174
• US Class Current: 438/53
• 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
• 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
• CPC Class Codes: G06F 3/047 using sets of wires, e.g. crossed wires

Abstract

A transparent force sensor for use in touch panel displays (touch screens) and method for fabricating the same are disclosed. The transparent force sensor is capable of detecting touch by measuring local pressure applied by a touch input to a display area of the touch screen.

Claims

1. A method of fabricating a force sensing sensor comprising:

forming a transparent polymer matrix including a plurality of transparent conducting nanoparticles, wherein forming the transparent polymer matrix comprises;

dispersing the plurality of transparent conducting nanoparticles in a first solvent system,

dispersing a transparent polymer in a second solvent system,

combining the first and second solvent systems in a predetermined ratio determined by a percolation value for the combination, and

degassing the combination;

disposing on a first surface of the transparent polymer matrix a first plurality of transparent conducting oxide (TCO) electrodes, the first plurality of TCO electrodes arranged in a first direction;

disposing on a second surface of the transparent polymer matrix opposing the first surface a second plurality of TCO electrodes, the second plurality of TCO electrodes arranged in a second direction overlaying the first direction, and

providing, by the transparent conducting nanoparticles at the cross section, a conducting path from the at least one of the first plurality of TCO electrodes to the at least one of the second plurality of electrodes, wherein, upon a force being applied at a cross section of at least one of the first and second plurality of TCO electrodes, the force can be measured by probing resistance at the cross section.

2. The method of claim 1, further comprising;

disposing the degassed combination on a substrate to form a dry film.

3. The method of claim 2, further comprising curing the dry film.

4. The method of claim 2, wherein degassing the combination comprises utilizing a vacuum chamber or ambient pressure to remove a gas from the combination.

5. The method of claim 2, wherein disposing the degassed combination on the substrate comprises spin coating, dip coating, or screen printing, or combinations thereof, the degassed combination on the substrate.

6. The method of claim 1, wherein the first solvent system comprises at least one of methyl ethyl ketone (MEK), Toluene, Methonal, 1-Phenoxy-2-Propanol (DPPH), and another solvent with similar solvent qualities.

7. The method of claim 1, wherein combining the first and second solvent systems comprises mixing the combination with a high speed mixer or shaker.

8. The method of claim 1, wherein the transparent conducting nanoparticles comprise indium tin oxide (ITO), zinc oxide (ZnO), tin dioxide (SnO2), or combinations thereof.

9. The method of claim 1, wherein the transparent polymer matrix comprises phenoxy resin, polyethers, acrylic, silicone, lacquer, or other types of transparent elastomers having similar properties, or combinations thereof.