Analysis of an in-plane electromagnetic energy harvester with integrated magnet array

In this paper, a novel MEMS electromagnetic energy harvester is designed, fabricated and tested. In-plane operation mode is utilized in the device to induce voltage in the coils, which enhances the changing rate of magnetic flux density across the coils. In order to produce larger magnetic flux density across the coil, magnetic properties of permanent magnets are simulated and optimized. Transient analysis of the induced voltage is conducted to prove the effectiveness of structural design. Comparison with the out-of-plane operation modes is carried out in the simulation, indicating that the in-plane operation mode not only enlarges the output, but also can make full use of the large vibration amplitude. In the fabrication process, instead of manually assembling bulk magnets, CoNiMnP hard magnetic alloy is electroplated onto the vibration plate. This method is MEMS compatible, which not only increases the production efficiency but also condenses the device's volume to 67.5 mm(3). Through experimental measurement, the proposed structure with integrated magnet array can generate 0.98 mV peak voltage at the frequency of 48 Hz. The maximum peak power density of this device reaches to 0.16 mu W/cm(3) with a 15.8 Omega external resistance. (C) 2014 Elsevier B.V. All rights reserved.