Capacitive pressure sensing using ionic film sensors

Abstract

Thin-film pressure sensors are disclosed herein. Such sensors include one or more electrodes in contact with a sensing material. As the sensor deforms the capacitance of the sensor varies and is measurable either between two electrodes of the sensor, or between the one electrode of the sensor and an electrode formed by the surface to which the sensor is applied, such as skin. The sensing material can be an ionic material such as an ionic composite including an ionic liquid.

What is claimed is: 
     
         1 . A sensor comprising:
 a housing defining a cavity therein, the housing including a top layer disposed between the cavity and the external environment of the housing, the top layer including a first membrane having an electrically conductive surface facing the cavity; and   a solid layer of a sensing material within the cavity, the sensing material being in contact with the electrically conductive surface of the first membrane.   
     
     
         2 . The sensor of  claim 1  wherein the top layer further includes a first electrically conductive layer and wherein at least part of the first electrically conductive layer provides the electrically conductive surface of the first membrane. 
     
     
         3 . The sensor of  claim 2  wherein the first electrically conductive layer comprises ITO. 
     
     
         4 . The sensor of  claim 2  wherein the first electrically conductive layer comprises graphene. 
     
     
         5 . The sensor of  claim 2  wherein the at least part of the first electrically conductive layer that provides the electrically conductive surface is patterned. 
     
     
         6 . The sensor of  claim 1  wherein the housing further includes an intermediate layer joined to the top layer, the intermediate layer including an aperture that defines the cavity. 
     
     
         7 . The sensor of  claim 6  wherein the housing further includes a bottom layer, wherein the intermediate layer is disposed between the top layer and the bottom layer. 
     
     
         8 . The sensor of  claim 7  wherein the bottom layer further includes an electrically conductive surface that faces, across the cavity, the electrically conductive surface of the first membrane. 
     
     
         9 . The sensor of  claim 8  wherein the bottom layer further includes a second electrically conductive layer and wherein at least part of the second electrically conductive layer provides the electrically conductive surface of the bottom layer. 
     
     
         10 . The sensor of  claim 7  wherein the bottom layer includes a second membrane disposed between the cavity and the external environment of the housing. 
     
     
         11 . The sensor of  claim 1  wherein the sensing material is patterned. 
     
     
         12 . The sensor of  claim 1  wherein the sensing material comprises an ionic material. 
     
     
         13 . The sensor of  claim 12  wherein the ionic material comprises a composite of a hydrogel matrix and an ionic liquid.