EXTREMELY MINIATURIZED CAPACITIVE MOVEMENT SENSORS USING NEW SUSPENSION SYSTEMS

An extremely miniaturized implantable capacitive accelerometer using novel suspension systems is presented. The main objectives are low power 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 capacitive sensing principle. In order to achieve the extreme miniaturization and also to improve the sensitivity, new suspension systems are investigated: torsional, meander- and spring-shaped beams. A very high sensitivity (5 mum/g) can be reached using the latter. The capacitance at rest is typically 4 pF and a DELTAC of 200% can be obtained. This new device combines the miniaturization demands with the simplicity of the technological process. The general design concept, electrical considerations and the most important fabrication steps are presented. With respect to the measuring system, the influence of d.c. and a.c. voltage supply is investigated in order to control the effective electrostatic forces.