Ti/PEDOT:PSS/Ti Pressure Sensor

This paper presents a wide dynamic range piezoresistive pressure sensor based on the conductive polymer PEDOT:PSS as the functional material. This is the first report on the PEDOT:PSS piezo-resistivity component measured in the direction perpendicular to the surface of the layer. The PEDOT:PSS layer is sandwiched between two layers of titanium. These Ti layers are the metallic electrodes of the device forming two ohmic contacts from the opposite sides to the layer. They are also thick and dense enough to protect the humidity-sensitive PEDOT:PSS layer from the detrimental effects of atmospheric humidity. The device is tested at normal atmosphere for its pressure sensitive properties. The electrical resistance of the device reproducibly change with the pressure in the range of 5 kPa to 2 MPa; above this range the device shows inelastic deformation, while below this range the response signals fail reliable detection. A model is presented which describes the pressure sensing mechanism based on the elastic deformation of the polymer which facilitates hopping of charge carriers from one chain to another.