Largely enhanced electrostatic generator based on a bipolar electret charged by patterned contact micro-discharge and optimized substrates

With the rapid development of wearable electronic devices and internet of things, harvesting mechanical energy from the surroundings to generate electric power has attracted intensive interests. Here, we demonstrate a rotary electrostatic generator based on a patterned positive and negative charged electret and optimal substrates of the electrode and electret. The bipolar charged electret is prepared using the patterned contact micro-discharge method with a pair of patterned electrodes. The generator obtains a double effective charge density by bipolar charging, which increases the output power by a factor of 4 compared to that of the conventional one based on unipolar charging. Moreover, the foam electrode substrate with the effective relative permittivity of 1.15 reduces the inherent capacitance of the generator, increasing the maximum average output power by a factor of 1.33 than that with a normal printed circuit board substrate. Totally, the maximum average output power of this generator is 5.3 times as high as that of the conventional one. In addition, we found that the electret substrate had a great influence on the output performance of the generator too, and there is an optimal electret substrate with the relative permittivity of 4.5. An electret substrate with low permittivity reduces the induced charge density on working electrodes of the generator, which contradicts the theory and requires further research.