Optimization of a vibrating MEMS electromagnetic energy harvester using simulations

Nowadays, wireless sensor networks (WSN) are becoming essential in our daily life. However, a major constraint concerns the energy power supply. Indeed, batteries need to be recharged or replaced often which implies a limited lifetime for WSN nodes. One alternative consists in harvesting mechanical energy from surrounding vibrations of the environment. Using finite element simulations, we report here a complete guideline to optimize a MEMS electromagnetic energy harvester consisting of an in-plane vibrating silicon frame supporting an array of micromagnets that faces a static 2D micro-coil. The dimensioning of the magnet array and the specific design of the coil are addressed, considering patterned 50 m thick NdFeB films with out of plane magnetization. The optimization of the electromechanical coupling which allows to efficiently convert the energy results from a trade-off between the high magnetic flux gradients produced by the micromagnets and the maximum number of turns of the facing coil.