Capacitive Pressure Sensor - A Simulation Study

A pressure sensor is an instrument which measures the force per unit area applied on the diaphragm of the sensor. There are various kinds of pressure sensors viz., piezoelectric, piezoresistive, resonant, strain gauge-based and capacitive pressure sensors. Of these, a capacitive pressure sensor is beneficial due to its high sensitivity, flexibility, low power consumption and potential applications in wearable and health monitoring. Hence, a normal mode absolute capacitive pressure sensor is taken into consideration in this study. This study presents a comparison of COMSOL Multiphysics software simulated data with the analytical data produced in MATLAB software. This study focuses on demonstrating the variations in diaphragm displacement, capacitance and sensitivity with respect to applied pressure, distance between capacitor plates and capacitor dimensions. The capacitive pressure sensors presented in this study are conventional and flexural beam-based capacitive sensors with vacuum dielectric sandwiched between polysilicon plates. The conventional capacitive pressure sensor exhibits a maximum sensitivity of 0.6092 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−5</sup>/kPa in 2000 kPa-4000 kPa range and the least sensitivity of 0.4547 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−5</sup>/kPa in 8000 kPa-10000 kPa range whereas, beam-based sensor has maximum sensitivity of 0.7078 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup>/kPa in 2000 kPa-4000 kPa thus, making the proposed capacitive pressure sensors suitable for large range applications. The conventional pressure sensor has a good limit of detection of 5 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−6</sup> Pa and both sensors' diaphragms demonstrate excellent repeatability of 2 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> loadingunloading cycles. The simulation and analytical data match well with each other highlighting the sensors' potential for use in weight sensing applications.