ELECTRET

http://www.audiocircuit.com/9041-esl-circuit/9041IMAI.htm

Basically the same as the electrostatic loudspeaker but without an outside power-supply. Works with charged electrons attracting and repelling each other. 

http://www.audiocircuit.com/9111-eshp-circuit/9111IMAI-CO.htmElectret

Solid electrically insulating, or dielectric, material that has acquired a long-lasting electrostatic polarization. Electrets are produced by heating certain dielectric materials to a high temperature and then letting them cool while immersed in a strong electric field. An electret is an analog of a permanent magnet.