A Method to Improve Sensitivity of Piezoresistive Sensor Based on Conductive Polymer Composite

An electrical bridge system based on differential structure is designed to improve the sensitivity of compressive pressure sensor based on the piezoresistivity of conductive polymer composite. As the sensor works in the condition where all of the subsensing elements have to bear the same pressure, the classical “excitation-induced differential structure” (i.e., the properties of the subsensing elements are the same, and they are arranged on the special positions to bear the reversed excitations) cannot be applied. To solve this problem, a “property-induced differential structure” (i.e., the subsensing elements are endowed with reversed properties by adjusting the mass ratio of conductive filler to polymer in the composite, and the responses of them are opposite when the pressure exerted on them are the same) is designed. If the mass ratio is lower/higher than the critical mass ratio, the destruction/formation effect of the conductive network of the composite is dominant under compression, inducing that the changing tendency of the resistance of the element is consistent/opposite to that of the pressure. By using the subsensing elements with reversed properties as the arms of a bridge, the pressure is converted to output voltage. The experimental results verify the feasibility of using the bridge system based on the “property-induced differential structure” to improve the sensitivity.