Design, fabrication and characterization of a highly symmetrical capacitive triaxial accelerometer

A highly symmetrical cubic capacitive triaxial accelerometer for biomedical applications has been designed, fabricated and characterized. The outer dimensions of the sensors are 5 mm × 5 mm × 5 mm. The devices are mounted on a standard IC package for easy testing. Features of the triaxial accelerometer are a highly symmetrical cubic structure, capacitive coupling of the high-frequency input voltage to the seismic mass, and the use of the polymer polydimethylsiloxane (PDMS) as spring material between the capacitor plates and the mass and polyimide (PI) as the flexible interconnection layer between the capacitor plates. The sensor structure and its basic operating principle, its mathematical mass-spring-damper model and the cleanroom technology necessary for the fabrication of the devices are described. The measurement results show a sensitivity of ~ 0.2V (m s−2)−1 with a corresponding resolution of 0.01 m s−2, an off-axis sensitivity of < 5%, a good linearity in the output voltage for accelerations up to at least 50 m s−2 and a bandwidth of d.c. to ~ 1 kHz.