A Thermal actuation device has at least a heat expandable or deformable material, a heater, a power supply for the heating, a thruster capable of movement following expansion or distortion of a material, so as to perform a substantially predetermined stroke having a length from a first to a second position,...http://www.google.com/patents/US6813886?utm_source=gb-gplus-sharePatent US6813886 - Thermal actuation device
