Electret MEMS Vibration Energy Harvester with Reconfigurable Frequency Response

We demonstrate a microelectromechanical systems (MEMS) electret-type vibrational energy harvester with a wide bandwidth between 25 and 60 Hz (span of 35 Hz) for a small sinusoidal acceleration of less than 10 mG (G = 9.8 m/s(2)). We have developed a method of tailoring the nonlinear characteristics by adjusting the mutual position of the opposing electrodes. Both soft-and hard-spring effects are realized, thereby further extending the frequency bandwidth between 25 and 95 Hz so that power can be effectively retrieved from extremely small vibrations of 10 mG. This reconfigurable nature of the developed harvester device is suitable for autonomous distributed sensors that obtain power from environmental vibrations.