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.