MEMS pressure sensor for gait analysis

Abstract

Pressure sensor plays an important role in many applications, especially in gait analysis. The focus of this dissertation is to design a pressure sensor to be applied onto the shoe insole. The piezoelectric effect is used to study the performance of the pressure sensor. This sensor is characterized by having a transduction element made of a piezoelectric material. Piezoelectric can be explained as one that produces an electric charge when a mechanical stress is applied. In this study, COMSOL Multiphysics 5.1 is used to design and simulate the piezoelectric pressure sensor. Two main piezoelectric materials, Lead Zirconate Titanate, PZT and Zinc Oxide, ZnO used as a surface layer of the circular diaphragm pressure sensor. Five different pressures of 10kPa, 1MPa, 2MPa, 3Mpa and 4MPa are applied onto the surface of the pressure sensor and compared with three different thickness parameters. The performance of the sensor studied based on the Von Mises stress, surface total displacement and electric potential produce on the pressure sensor design. An overall results focus on the maximum thickness of 60um with applied pressure of 4MPa. The result shows that surface total displacement will be high when the pressure applied were increased, but decreased in thickness of piezoelectric material. The surface total displacement obtained for PZT and ZnO are 1.79 x 10 -3 um and 1.09 x 10 -3 um . Then, the Von Mises stress shows that when the applied pressure is increased, the stress produces also increased but the thickness parameter must be decreased. ZnO produces a greater effect or higher stress compared to PZT as ZnO produces 5.24MPa compared to PZT that only produce 4.11MPa. An electric potential between the materials shows that output voltage increased when the pressure increased with decreasing of the thickness. The higher electric potential produce is 15.9848V come from the material ZnO while PZT only produce 2.7659V with the same pressure applied. As conclusion, both materials can be applied in this design as it followed the pressure sensor specifications.