Design and sensitivity analysis of capacitive MEMS pressure sensor for blood pressure measurement

Abstract

This paper presents the design and simulation of a MEMS based clamped capacitive pressure sensor for blood pressure measurement. Normally, Blood pressure for human beings varies in the range of 0.1–0.14 MPa. The operating range of this sensor design, modified according to the dimensions, is between 0 and 0.16 MPa. The diaphragm deflects on application of pressure which triggers a change in the capacitance between diaphragm and bottom electrode. The plates are separated by a dielectric medium ( $$ Si_{3} N_{4} $$ ). The change in capacitance, capacitive sensitivity and diaphragm deflection are observed for every design model to determine its performance. To improve the sensor performance, parameters like separation gap and diaphragm thickness are varied. The length and width of square diaphragm and overlapping area (A) are constant for all the designs. Small deflection theory ( $$ w_{\hbox{max} } = {h \mathord{\left/ {\vphantom {h 4}} \right. \kern-0pt} 4} $$ ), pull-in voltage phenomena ( $$ w_{\hbox{max} } \le {g \mathord{\left/ {\vphantom {g 4}} \right. \kern-0pt} 4} $$ ), and thin plate theory ( $$ h \cong a/10 $$ ) have been considered while designing the model. With respect to pressure, the simulation of diaphragm deflection is performed in COMSOL Multiphysics and analytical simulation for Change in capacitance and Capacitive sensitivity is performed in MATLAB.