EXTREMELY MINIATURIZED CAPACITIVE MOVEMENT SENSORS USING NEW SUSPENSION SYSTEMS

An extremely miniaturized implantable capacitive accelerometer using n ovel suspension systems is presented. The main objectives are low powe r consumption, high sensitivity and very small size (1.5 mm X 1.2 mm x 1.3 mm). Low power consumption can be achieved by selecting the capac itive sensing principle. In order to achieve the extreme miniaturizati on and also to improve the sensitivity, new suspension systems are inv estigated: torsional, meander- and spring-shaped beams. A very high se nsitivity (5 mum/g) can be reached using the latter. The capacitance a t rest is typically 4 pF and a DELTAC of 200% can be obtained. This ne w device combines the miniaturization demands with the simplicity of t he technological process. The general design concept, electrical consi derations and the most important fabrication steps are presented. With respect to the measuring system, the influence of d.c. and a.c. volta ge supply is investigated in order to control the effective electrosta tic forces.