Fully-integrated micro-solenoid with closed magnetic circuit for high power density of MEMS Electromagnetic Vibration Energy Harvester

This letter presents a highly-efficient micro-solenoid integrated with closed magnetic circuit to enhance the power density of MEMS electromagnetic energy harvester. Compared with most MEMS electromagnetic energy harvester adopting air-cored planar coil, high permeability closed magnetic circuit is specifically designed, and integrated inside the micro-solenoid with multiple wire turns for higher electromechanical coupling, contributing to the effective increased power density of MEMS energy harvester. Moreover, the wafer-level micro-solenoid is compatible with nonlinear spring, which brings higher power output over wideband frequency range. At acceleration of 1 g, the prototype shows load power of 265.2 W and normalized power density of 5.9 mWcm-3g-2 with load resistance of 40.1, accompanied with half-power bandwidth of 30 Hz. The fully-integrated solenoid is compatible with other soft magnetic material and frequency broadening mechanism, providing adequate potential for comprehensive performance enhancement of MEMS electromagnetic energy harvester.