Dynamic behavior of MEMS variable capacitor for autonomous biometric sensors

The influence of spring element profile obtained by deep reactive ion etching on dynamic behavior of MEMS variable capacitor for electrostatic vibration energy harvester is studied. It is found that the vibration resonance frequency of the capacitor movable electrode is decreased with increasing the side subetching angle, whereas the vibration amplitude is increased with increasing this angle. A slight out-of-plane swinging of inertial mass is also observed for all three structures caused by the non-uniform compression and tension of the spring elements, the greater swinging was observed for subetched structures.