A millimeter-sized electret-energy-harvester with microfabricated horizontal arrays and vertical protrusions for power generation enhancement

This paper describes a millimeter-sized electret vibrational energy harvester fabricated by a MEMS-based process for power generation enhancement. To increase current generation, we developed a new “slit-and-slider” structure with horizontal arrays and vertical protrusions. This structure enables us to increase an area and to narrow a gap of energy conversion in the limited size. The structure was fabricated by gold-electroplating. A lower chip with a movable part and an upper chip with a fixed part were aligned by chip-on-chip mounting. The device resonated around 1430 Hz with an acceleration amplitude of 6 m/s². With an ethylene-tetrafluoroethylene copolymer electret film, nanoampere-level AC current was generated.