A new vibration-driven miniature generator can deliver 20 times as much energy in proportion to its size as existing button batteries. The generator, developed by Toshiyuki Ueno of Kanazawa University in Japan, measures less than half an inch. It consists of two pieces of the magnetostrictive material galfenol, with weights added. Influenced by weak vibration, the weights are displaced, affecting the galfenol pieces and generating power. It could eventually be used in small electrical devices.