Parylene-based electret power generators

An electret power generator is developed using a new electret made of a charged parylene HT (R) thin-film polymer. Here, parylene HT (R) 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 (R) 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 (R), 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 mu W, is obtained at 50 Hz with an external load of 80 M Omega. For low frequencies, the generator can harvest 7.7 mu W at 10 Hz and 8.23 mu W at 20 Hz.