Linear freestanding electret generator for harvesting swinging motion energy: Optimization and experiment

Nowadays, harvesting mechanical energy from body motion for powering wearable electronics has gained great attention. Swinging motion is a common motion in the human body. Herein, we demonstrate a linear grating-structured freestanding electret generator with the electrodes as the slider for harvesting arm swinging energy. The analytical solutions of the outputs of the generator under uniformly accelerated motion are obtained from its theoretical model. It is verified that the formula of average power under uniform motion can be used to estimate the matched load resistance and optimize the parameters of the generator under uniformly accelerated motion, and the optimized results are independent of the motion mode. The generator gets the maximum power when the effective length of the slider is half that of the stator and can double the output power compared with conventional generators with electrodes as the stator. We optimized the generator by taking the fringe effect of the electric field and the parasitic capacitance into consideration, and the optimized generator generates tens of microwatts of power from arm swinging.