Characteristics of a highly symmetrical miniature capacitive triaxial accelerometer

A highly symmetrical cubic capacitive triaxial accelerometer for biomedical applications has been designed, realised and tested. The sensors are available in two outer dimensions, namely 2×2×2 and 5×5×5 mm³. The devices are mounted on a standard IC package for easy testing. Features of the sensor are a highly symmetrical cubic structure, capacitive coupling of the high frequency input voltage to the seismic mass and the use of the polymers polydimethylsiloxane (PDMS) as spring material between the capacitor plates and the mass and polyimide (PI) as flexible interconnection layer between the capacitor plates. The sensor structure and its basic operating principle, its mathematical mass-spring-damper model and the necessary cleanroom technology are described. The measurement results show a sensitivity of ~0.15 V/(m/s²) with a corresponding resolution of 0.01 m/s², an off-axis sensitivity of <5 %, a good linearity in the output voltage for accelerations up to at least 50 m/s² and a bandwidth of DC 500 Hz