An implantable capacitive pressure sensor for biomedical applications

Cuff electrode is an indispensable component of a neural prosthesis system. It is often employed to apply electrical stimuli on motor nerve fibers that innervate muscles or alternatively to record neural signals from the peripheral nerves. It is reported that a pressure over 20 mmHg is harmful for the nerve trunk. Therefore, measuring the interface pressure between the cuff and a nerve trunk provides a means to monitor the health of the nerve tissue. The goal of this study is to develop a micro capacitive pressure sensor which can be embedded into the cuff electrode for in situ monitoring of the interface pressure between implanted cuff and nerve tissue. By a compromise between the performance and size, the final design with a dimension of 7000 μm × 7000 μm, a range of measurement from 0 to 20 mmHg, and a sensitivity of 10-14 pF/(pF mmHg) is fabricated and tested in the study. The calibration results revealed two important design factors, namely, the geometric properties of dielectric layer and the thickness of insulating layer for developing the pressure sensor.