Improving an electret transducer by fully utilizing the implanted charge

Most of the countercharge in the conventional electret-based electromechanical transducer, where the electret is formed on a conducting or semiconducting substrate, is induced in the substrate. Here we introduce a type of electret transducer that contains a freestanding electret without a conducting substrate, thereby enhancing the electric field between the electret and the electrodes where the output current is generated. A measurement of the power output from an electromechanical transducer yielded approximately five times larger power when a freestanding electret film was used than when the same electret material was deposited on a conducting substrate.