Modeling the Flexible Capacitive Pressure Sensor with a Polymer Composite Dielectric Layer

F1exible pressure sensors are important in applications of flexible electronics. Although extensive efforts have been made to improve the performance of pressure sensors through materials fabrication or circuitry design, the effect of loading mode on the sensor response has rarely been discussed before. In this study, an appropriate constitutive relationship of the composite material that is used as the dielectric layer in capacitive pressure sensors was characterized via tensile tests, thereby ensuring the stresses in the film sensor under a pressure can be simulated accurately by the finite element analysis. The stresses under the pressure head, as a major factor to affect the capacitance variation, were further fitted by a polynomial equation in terms of the variation of the capacitance of the film sensor with a designed experiment for both measuring the capacitance and force. The equation supports an empirical model that reveals the capacitance of the film sensor can be estimated directly when the stress in the sensor is obtained. The model helps to develop a new pressure sensor applied in flexible devices.