Multi-Conceptual Mechanical Design Optimization of Capacitive Pressure Sensors via Finite Element Analysis with use of Anisotropic Behavior of Silicon <111> Crystal: Summary of Design Optimization Approaches

Abstract

In the world of micro-mechanical design of micro-sensors, up to date, there has not been substantial considerations given to the actual mechanical or structural aspect of the designs. Hence, most of the currently available designs are challenged to linearize the “non-linear” sensor’s output by utilization of electronic circuitry. In this research work, a micro-pressure diaphragm which possess linear pressure-deflection behaviour is designed via FEM optimization techniques. The diaphragm is modelled as a Silicon (111) plane, which possess plane isotropic properties. A circular centre boss section is added to the diaphragm and optimization is carried out, to achieve an optimum diaphragm geometry that would allow for flat or rigid deflection of this boss section under the applied surface pressure loading. The approximate closed−form deflection solutions are developed using the anisotropic thin plate theory and the diaphragm deflection behaviour of the FEM optimized design is compared with this thin plate theory model. This diaphragm design is proposed to be used as the top electrode plate of a capacitive pressure sensor, where linear pressure-capacitance change behaviour would become present. This pressure diaphragm has a pressure range of 0 to 206843 Pa (30 psi) with a pressure resolution of 689.5 Pa (0.1 psi).