Electrostatic/triboelectric hybrid power generator using folded electrets

Recently, electret-based electrostatic and triboelectric energy harvesting devices have demonstrated their great potential in converting ambient mechanical energy to electrical energy due to their merits of low cost, easy formation and long-term stability. For electret-based generators, the performance of the state-of-the-art MEMS energy harvesters mostly falls into the range of nW or μW level, limiting their potential applications. For triboelectric generators, the output power is severely constrained by the effective surface charge density that only relies on the contact triboelectrification. Herein, we demonstrate a hybrid power generator with folded electrets, which takes the merits of non-contact electrostatic induction by high residue charge within electrets as well as contact triboelectrification by increased surface area. High output power can be readily achieved. Triggered by gentle finger tapping, the instantaneous peak-to-peak output voltage and short-circuit current of up to 1000 V and 0.11 mA have been achieved, which are capable of directly lighting up hundreds of off-the-shelf LEDs. The outcome of this work demonstrates the possibility of using such hybrid generators for wearable and portable electronics.