Piezo Based Force Sensing

Abstract

Systems for detecting an amount and/or location of a force applied to a device using a piezoelectric film are provided. One example system can include a transparent piezoelectric film for generating an electric charge in response to a deformation of the film. Electrodes positioned on opposite surfaces of the piezoelectric film can be used to detect the generated electric charge and determine an amount and/or location of force applied to the film based on the generated electric charge. In another embodiment, the system can include a capacitive touch sensor for determining a location of a touch event on the device.

1 - 20 . (canceled) 
     
     
         21 . A display stack, comprising:
 a cover material defining an outer surface of the display stack and configured to receive a touch input from a user;   a touch input sensor substrate below the cover material;   a first touch input sensor electrode disposed on a first surface of the touch input sensor substrate;   a second touch input sensor electrode disposed on a second surface of the touch input sensor substrate;   a light-emitting layer below the touch input sensor substrate;   a force sensor layer below the light-emitting layer;   a first force sensor electrode disposed on the force sensor layer;   a second force sensor electrode disposed on the force sensor layer and aligned with the first force sensor electrode; and   sense circuitry operable to detect an electric charge generated by the force sensor layer in response to a deformation of the force sensor layer and the light-emitting layer that results from the touch input.   
     
     
         22 . The display stack of  claim 21 , wherein:
 the touch input sensor is coupled to the cover via a first adhesive layer;   the light-emitting layer is coupled to the touch input sensor a second adhesive layer; and   the force sensor layer is coupled to the light-emitting layer via a third adhesive layer.   
     
     
         23 . The display stack of  claim 22 , wherein the first adhesive layer and the second adhesive layer comprise an optically clear adhesive. 
     
     
         24 . The display stack of  claim 21 , wherein the light-emitting layer is an organic light emitting diode display. 
     
     
         25 . The display stack of  claim 21 , wherein the first touch input sensor electrode is capacitively coupled to the second touch input sensor electrode. 
     
     
         26 . The display stack of  claim 21 , wherein the first touch input sensor electrode and the second touch input sensor electrode are formed from a transparent conductive material. 
     
     
         27 . The display stack of  claim 21 , wherein the force sensor layer comprises a piezoelectric material. 
     
     
         28 . A display stack, comprising:
 a touch input sensor comprising:
 a transparent substrate; 
 a first touch input sensor electrode array disposed on a first surface of the transparent substrate; and 
 a second touch input sensor electrode array disposed on a second surface of the transparent substrate opposite the first touch input sensor electrode array; 
   an organic light-emitting diode display layer coupled to the touch input sensor;   a force sensor coupled to the organic light-emitting diode display layer and comprising:
 a piezoelectric substrate; 
 a first force sensor electrode array disposed on the piezoelectric substrate; and 
 a second force sensor electrode array disposed on the piezoelectric substrate adjacent to the first force sensor electrode array; and 
   sense circuitry operable to detect an electric charge generated by the force sensor in response to a deformation of the light-emitting layer that results from a touch input to the touch input sensor.   
     
     
         29 . The display stack of  claim 28 , wherein:
 the first touch input sensor electrode array is disposed in a first pattern; and   the second touch input sensor electrode array is disposed in a second pattern.   
     
     
         30 . The display stack of  claim 29 , wherein:
 the first pattern comprises a first set of parallel electrodes; and   the second pattern comprises a second set of parallel electrodes perpendicular to the first set of parallel electrodes.   
     
     
         31 . The display stack of  claim 28 , wherein the first force sensor electrode array comprises a grid of individual electrodes. 
     
     
         32 . The display stack of  claim 31 , wherein the second force sensor electrode array comprises a grid of individual electrodes. 
     
     
         33 . The display stack of  claim 28 , wherein:
 the piezoelectric substrate is a first piezoelectric sheet; and   the display stack comprises:
 a second piezoelectric sheet below the first piezoelectric sheet; and 
 a third force sensor electrode array disposed between the second piezoelectric sheet and the first piezoelectric sheet. 
   
     
     
         34 . The display stack of  claim 33 , wherein the second force sensor electrode array comprises a grid of individual electrodes. 
     
     
         35 . The display stack of  claim 33 , wherein the third force sensor electrode array comprises a shared ground electrode. 
     
     
         36 . A display stack, comprising:
 a transparent outer cover;   a light-emitting layer below the transparent outer cover; and   a force sensor adhered to the light-emitting layer and comprising:
 a first force-sensing film; 
 a first force sensor electrode array disposed on a first surface of the first force-sensing film; 
 a shared electrode disposed on a second surface of the first force-sensing film, the second surface opposite the first surface; 
 a second force-sensing film coupled to the shared electrode; and 
 a second force sensor electrode array disposed on the second force-sensing film opposite the shared ground electrode. 
   
     
     
         37 . The display stack of  claim 36 , wherein the shared ground electrode is coupled to circuit ground. 
     
     
         38 . The display stack of  claim 36 , wherein:
 the first force-sensing film comprises a first piezoelectric material; and   the second force-sensing film comprises a second piezoelectric material.   
     
     
         39 . The display stack of  claim 38 , wherein the first piezoelectric material is the same as the second piezoelectric material. 
     
     
         40 . The display stack of  claim 36 , further comprising a transparent capacitive touch input sensor adhered to the protective outer cover and positioned above the light-emitting layer.