Energy harvesting by MEMS vibrational devices with electrets

This paper presents experimental proof of energy harvesting with MEMS-based vibrational devices. To clarify the effect of the coupling of vibration of MEMS devices and electrical field of electrets for current generation, a slit-and-slider structure was developed. This structure enables to combine the MEMS devices and electrets after their vibrational and electrical properties have been characterized separately. In the fabrication, the movable gold electrodes were released and then aligned by chip-on-chip mounting to face the fixed electrodes. A 1-mm-square electrode resonated around 1166 Hz with external vibration of a magnitude of acceleration of 1 m/s². The surface and rear potentials of the electret were around -150 and +100 V, respectively. The coupling of the mechanical and electrical properties produced an AC current of 170 pA. The results pave the way to designing and fabricating small-sized vibrational energy harvesters.