A permanent-soft magnetic coupled bi-stable architecture for high-performance MEMS electromagnetic energy harvester

Abstract

This paper presents a novel permanent-soft magnetic coupled bi-stable architecture for high-performance MEMS electromagnetic energy harvester. With comprehensive consideration from both aspects of electrical and mechanical component, permalloy magnetic circuit is integrated inside micro-solenoid, which could not only bring increased wire-turns, but also enable strengthened flux density inside micro-solenoid. Moreover, magnetization-reversible of closed magnetic circuit could be enabled with cooperation of antiparallelly-positioned magnetic pair, which is beneficial for higher electromechanical coupling effect by maximizing flux variation rate. Furthermore, with specific mechanical stiffness tuning of the developed bi-stable architecture, barrier depth and well gap could be separately adjusted for spectrum tuning of high-energy inter-well oscillation, and thus induce high-level electromechanical coupling maintaining within wideband low-frequency region. Analytical and experimental result consistently demonstrate that 10-times increased electromechanical coupling of 0.14 could be achieved compared to the counterpart adopting air-cored solenoid, which brings 6 times and 37 times increased in voltage (82.8 mV) and power output (163.2 μW), respectively. Moreover, at weak excitation with acceleration of 0.5 g, the fully-integrated prototype shows continuous inter-well oscillation bandwidth of 74 Hz (24–98 Hz), which covers 74 % frequency region below 100 Hz. Furthermore, with batch-fabrication process, tremendous normalized power density of 1.8·10⁴μW·cm⁻³·g⁻² could be achieved within such wideband frequency spectrum, showing adequate potential application in harvesting weak vibration energy widely distributed in industrial production and daily life.