Electromechanical analysis of a piezoresistive pressure microsensor for low-pressure biomedical applications

The electromechanical analysis of a piezoresistive pressure microsensor with a square-shaped diaphragm for low-pressure biomedical applications is presented. This analysis is developed through a novel polynomial model and a finite element method (FEM) model. A microsensor with a diaphragm 1000 mu m length and with three different thicknesses (10, 15, and 20 mu m) is studied. The electric response of this microsensor is obtained with a Wheatstone bridge of four p-type piezoresistors located on the diaphragm surface. The diaphragm that is 10 mu m thick exhibits a maximum deflection of 3.74 mu m using the polynomial model, which has a relative difference of 5.14 and 0.92% with respect to the Timoshenko model and the FEM model, respectively. The maximum sensitivity and normal stress calculated using the polynomial model are 1.64 mV/V/kPa and 102.1 MPa, respectively The results of the polynomial model agree well with the Timoshenko model and FEM model for small deflections. In addition, the polynomial model can be easily used to predict the deflection, normal stress, electric response and sensitivity of a piezoresistive pressure microsensor with a square-shaped diaphragm under small deflections.