Implantable bimorph piezoelectric accelerometer for feedback control of functional neuromuscular stimulation

This paper describes the design, fabrication and testing results of a novel bimorph piezoelectric accelerometer (built on a parylene beam with ZnO film) and its application in an injectable neuromuscular stimulator (BION/spl trade/). In order to control limb motion using such stimulation, it is necessary to sense the acceleration of the body or its inclination with respect to the gravitational field. This paper describes a MEMS piezoelectric accelerometer that meets the requirements of this application, which include small size, extremely low power consumption, simple detection circuit and high sensitivity. The unamplified sensitivity of the bimorph piezoelectric accelerometer is around 7.0 mV/g and the minimum detectable signal level is around 0.01 g. The working frequency range is from 60 Hz down to sub Hz with high linearity of the sensitivity.