Reversible shape memory alloy film fabricated by RF sputtering

The fabrication and processing of an actuator with a TiNi Shape Memory Alloy (SMA) film are discussed and demonstrated. TiNi SMA films were deposited by using sputter deposition techniques, patterned and etched. These films were solution-treated and aging-treated, and then an inverse force layer of chromium was deposited on a SMA film. The frequency response of the beam type actuator was measured by resistance heating. The maximum amplitude was in proportion to the inverse force, and was therefore controlled by chromium thickness. The maximum displacement slightly decreased with an increase of frequency. The minimum displacement suddenly increased at more than 0.1 Hz, then showed a stability over 5 Hz. The maximum displacement was not decided by chromium thickness but TiNi thickness, because thickness of the latter was fifteen to forty times larger than that of the former. Because the frequency response depended on the heat radiation of an actuator, TiNi thickness was the most important factor to the actuation.