MEMS-Based capacitive strain sensor for cervical spinal fusion monitoring- design and optimization approach

Abstract

This paper describes the design, simulation, and fabrication method of a MEMS-based capacitive strain sensor to optimize cervical spinal fusion monitoring. Four sensing techniques—piezoresistive, piezoelectric, contact-resistive, and capacitive- were experimented and the capacitive strain sensor was selected due to its higher sensitivity, linearity, and potential for wireless integration. The sensor was optimized for key parameters, including electrode gap and metal coverage, to a final 6 μm gap and full metal coverage using COMSOL Multiphysics. A stable fabrication process was then developed using gold electrodes aligned using anodic bonding with silicon and borosilicate glass substrates. The final sensor also offers high sensitivity, excellent mechanical stability, and biomedical implantability compatibility, giving a reliable real-time tracking method for spinal fusion progression.