Novel MEMS Piezoresistive Sensor with Hair-Pin Structure to Enhance Tensile and Compressive Sensitivity and Correct Non-Linearity

Abstract

This work focuses on enhancing the sensitivity and reducing the wheatstone bridge non-linearity of the current designs of Micro-Electro-Mechanical systems pressure sensor. Conventionally there are four piezoresistors on the four edges of a square diaphragm. These four peizoreistors give rise to a change in resistance with input stress which is converted to voltage using a wheatstone bridge so that it can be measured. In this renewed proposed design, there are a total of eight sensors on the diaphragm; four dedicated to the compressive and tensile stress on the XX – plane and the other four for the YY – plane. Compressive and tensile forces have similar magnitude but act in opposite directions which isn’t considered in the conventional designs, leading to non-linearity. Thus the non-linearity due to the sign difference in compressive and tensile forces is accounted for by calculating them separately and doubling the sensitivity. Each of these eight sensors include two piezoresistors; one attached to the diaphragm and the other outside forming a hairpin structure. Instead of using the wheatstone bridge for measuring the voltage, we make use of operational amplifiers. Thus removing the wheatstone bridge non–linearity.