Modelling and simulation of TMCPS using PMMA

Abstract

In this paper, a mathematical modeling of the Touch Mode Capacitive Pressure Sensor (TMCPS) is presented and validated by using the COMSOL Multiphysics simulator. The output characteristic of TMCPS is linearized and thereby achieved by using a mechanical coupler which is utilized to convert the deflection of the diaphragm due to applied pressure into a linear displacement. A square diaphragm is designed for conversion of pressure into displacement to calculate the maximum deflection of the square diaphragm and the output capacitance of the sensor. A 3D model of the design sensor is built and simulated using a COMSOL Multiphysics simulator to compare the calculated values and simulated output values. The various factors affecting the sensitivity of TMCPS: the physical parameters of the diaphragm, mechanical properties (Poisson's ratio &Young modulus), permittivity of the polymer, physical parameters of the capacitor plates, and gap between the capacitor plates are considered to validate the values. The sensitivities of the Poly-Methyl Methacrylate (PMMA) based TMCPS with a diaphragm thickness of 20 µm for simulated and calculated are found as 0.035fF/MPa and 0.034 fF/MPa respectively.