A multi-frequency vibration-based MEMS electromagnetic energy harvesting device

• A multi-frequency vibration-based MEMS electromagnetic energy harvesting (EH) device has been proposed.
• The vibration energy of the device under three excitation frequencies of 840, 1070 and 1490 Hz has been investigated.
• The optimal power densities of 0.157, 0.014 and 0.117 μW/cm3 have been achieved at these three frequencies at 1.0 g.

A multi-frequency vibration-based MEMS electromagnetic energy harvesting (EH) device has been presented, fabricated and characterized in this paper. It consists of a permanent magnet and a circular suspension structure on a MEMS EH chip. By emulating the magnetic field of a cylinder magnet, the gap distance between the magnet and EH chip is optimized to be zero for achieving larger magnetic flux change and higher output performance. From the experimental results, the vibration energy can be harvested at three excitation frequencies of 840, 1070 and 1490 Hz, which corresponds to the out-of-plane (mode I), torsion (mode II/III) and in-plane (mode IV/V) vibrations of the EH device, respectively. The maximum power densities at these three frequencies are 0.157, 0.014 and 0.117 μW/cm3, respectively, for a matched load resistance of 626 Ω and an input acceleration of 1.0 g. The feasibility study results show promising application potentials for harvesting energy from vibrations of multi-frequency.