Electromagnetic energy harvester with an in-phase vibration bandwidth broadening technique

This paper reports a duo-mode vibration structure for increasing usable bandwidth in a micromachined electromagnetic energy harvester. The energy harvester is characterized by using finite element analysis on the vibration frequency and amplitude. Since a spiral diaphragm is much more flexible than a cantilever diaphragm for a given size, a spiral is inserted in to a U-shape cantilever, forming the proposed energy harvester. By designing the coupled structure, not only the resonance frequency is reduced, but also the usable bandwidth is broadened. Experimental results show that the device generates electromotive force of 1.00 and 1.03 mV, 7.66 and 7.43 nW (into 27 Ω load) at two resonance frequencies at 211 and 274 Hz, respectively.