Design and simulation of a MEMS capacitive bending strain sensor using dielectric materials for spinal fusion monitoring

The design and simulation of an MEMS-based capacitive bending strain sensor using silicone dope as a plate is presented in this paper. The objective is to design and simulate the performance of a strain sensor using a dielectric material between capacitive plates. The silicone dioxide (SiO₂) and polydimethylsiloxane (PDMS) was utilized as the dielectric layer in this model. Several dimensions of the sensor and the dielectric materials were studied as silicon dioxide was also used to increase the performance of the sensor. The application of the sensor is for the spinal fusion monitoring system. The finite element analysis (FEA) was performed using MEMS CoventorWare 2008, and the results were verified using the analytical method. Based on simulation results, the presences of the dielectric material has increased the capacitance output of the sensors and produced greater sensitivity. The sensitivity of the sensor is 24.9-44.48% higher compared with existing sensors. The nominal capacitance of the sensor also improved significantly from 94.16pF to 156.14pF. The sensor also exhibits greater sensitivity at the early stage of the bending strain; the sensitivity of the sensor is up to 0.525pF/με.