Light driven motor using shape memory alloy

A light-driven motor driven by a single source of light is demonstrated for the first time. The system utilizes a NiTi shape memory alloy (SMA) wire initially trained straight shape. The SMA wire was formed in a loop and put around two wheels. The wire undergoes change in the radius of curvature as it rotates, and when light is irradiated at the point where the wire is leaving the wheel, it undergoes phase transition and straighten: causing a rotating force to the wheel. In the experiment a rotational speed of 135 to 140 rpm was observed at the smaller wheel for a single loop of 0.3 mm-diameter SMA wire.