An Electromagnetic Translational Vibration Energy Harvester Fabricated in MP35N Alloy

This paper presents a mechanically-robust high-power-density electromagnetic vibration energy harvester fabricated from MP35N alloy. Its primary focus is on the use of MP35N alloy, and the corresponding performance. It follows our prior work on a similar harvester fabricated in silicon that now provides a performance baseline. The optimized design flow developed in our prior work is applied here, yielding mechanical, electrical, and magnetic design decisions, and harvesting performance, that remain largely unchanged. Importantly, while supporting comparable harvesting performance, the new material significantly improves robustness and ruggedness as needed for practical applications. The MP35N harvester suspension is fabricated using a combination of water-jet and electrical-discharge machining. The resulting harvester has an active volume of 1.81 cm
³
, and an output power P
_Out
of 1.26 mW at 1.08 g and 107.7 Hz under matched load. This yields a power density (PD) of 0.7 mW/cm
³
and a normalized power density (NPD) of 0.6 mW/cm
³
/g
²
. Importantly, the new harvester survives a 6-foot drop, and ordinary handling during fabrication and operation. The addition of backiron is shown to reduce magnetic-path reluctance, increase magnetic coupling, and thus increase output power. The harvester with backiron has an active volume of 2.17 cm
³
, and a P
_Out
of 2.2 mW at 1.3 g under matched load, yielding a PD of 1.01 mW/cm
³
and an NPD of 0.6 mW/cm
³
/g
²
.