A leaf of suitable dielectrical material bears, trapped on one at least of its two surfaces, equal or substantially equal amounts of positive and negative electrostatic charges, these charges being preferably injected into the leaf by successive ionization in reverse directions of gaseous layers against...http://www.google.co.uk/patents/US4093884?utm_source=gb-gplus-sharePatent US4093884 - Thin structures having a piezoelectric effect, devices equipped with such structures and in their methods of manufacture
