Torsional Electromagnetic Vibrational Energy Harvester Based on Stacked Flexible Coils

In this work, we report on an electromagnetic vibrational energy harvester (EVEH), based on the torsional movement of a permanent magnet over a stack of flexible planar coils. The disc magnet is glued to a silicon plate suspended by straight torsional springs. With a size of 1 cm×1 cm×1.08 cm, the proposed EVEH is capable of generating an open-circuit peak-to-peak voltage of 138.9 mV and a power of 4.6 μW, under a sinusoidal excitation of ±0.5g and frequency of 104 Hz. At elevated acceleration levels, the maximum peak-to-peak output voltage is 185.2 mV under the acceleration of 7g (±3.5g).