Parylene-based electret power generators

An electret power generator is developed using a new electret made of a charged parylene HT® thin-film polymer. Here, parylene HT® is a room-temperature chemical-vapor-deposited thin-film polymer that is MEMS and CMOS compatible. With corona charge implantation, the surface charge density of parylene HT® is measured as high as 3.69 mC m−2. Moreover, it is found that, with annealing at 400 °C for 1 h before charge implantation, both the long-term stability and the high-temperature reliability of the electret are improved. For the generator, a new design of the stator/rotor is also developed. The new micro electret generator does not require any sophisticated gap-controlling structure such as tethers. With the conformal coating capability of parylene HT®, it is also feasible to have the electret on the rotors, which is made of either a piece of metal or an insulator. The maximum power output, 17.98 µW, is obtained at 50 Hz with an external load of 80 MΩ. For low frequencies, the generator can harvest 7.7 µW at 10 Hz and 8.23 µW at 20 Hz