Design and fabrication of low-pressure piezoresistive MEMS sensor for fuel cell electric vehicles

This research focuses on the design and fabrication of a MEMS-based pressure sensor to measure the internal pressure of a thermal management system for fuel cell electric vehicles. The principle of measurement of the pressure is converting the piezoresistor value on a diaphragm deformed by a pressure difference into an output voltage. The diaphragm should operate normally for pressure sensing even harsh environments such as those in automobiles. However, the pressure sensor outputs abnormal values with an offset voltage due to physical and chemical factors during driving. One of the reasons is the polymer reaction originating from the coolant of the thermal management system between the polymer and sensor diaphragm. In this paper, the reason for abnormal operation is analyzed by measurement with a microscope, computational fluid dynamics, finite element method, and reproducible tests. A solution is suggested and a revised pressure sensor is proposed.