Micromachining process for thin-film SMA actuators

Shape memory alloy (SMA) actuators can produce large displacement/force and are robust against external overload. Their structure is simple because an SMA element serves as both structural and functional (actuation) parts. One drawback has been the difficulty in micromachining of SMA. This paper deals with the deposition of thin films, heat treatment and patterning of TiNi SMA. Microactuators were fabricated by the process. Typical dimensions of the actuator were 10 μm in thickness, 30 μm in width and 800 μm in length. They produced large displacement of more than a few hundred micrometers and large force of more than 5 mN. Repeatable motion up to 20 Hz was observed for the loop actuator composed of two SMA cantilevers