US Patent 7444812 Shape memory alloy MEMS heat engine

A microelectromechanical systems (MEMS) based heat engine capable of converting thermal energy gradients into mechanical or electrical energy, as well as its fabrication process is disclosed. This heat engine design consists of a stressed oscillating beam formed from a shape memory alloy (SMA) thin film. As the temperature of the beam changes, its shape changes due to the phase transformation of the shape memory alloy, causing it to oscillate between a hot source and a cold source. Due to the hysteretic behavior of the phase transformation, the oscillating SMA cantilever beam produces a net mechanical work output that may be either converted to electrical energy or mechanically linked to other MEMS devices.