Two thin film shape memory alloy microactuators

Abstract

The deposition and processing of thin film Shape Memory Alloy (SMA) is presented. By using sputter-deposition technique, 8 to 10µm thick films of TiNi were deposited. Among the features of the thin film SMA, the following can be noticed: large recovery strain; the relation between recovery strain and electrical resistance change of the TiNi alloy, allowing to use the TiNi as a position sensing element; long lifetime; large force-displacement product; high power-weight ratio; simple structural design; and low voltage operation. Therefore, a SMA two way loop actuator as well as a XY stage have been realized. Lift off technique is used to obtain the desired shape of two SMA microactuators. Two SMA cantilevers were folded up from the substrate and bound each other, making a three-dimensional loop. By activating each lever alternately, a SMA two-way actuator was realized. The dimensions of the loop actuator were 2 mm in length and 600µn in height. The loop actuator has been successfully operated. It features repeatable motion up to 20Hz and maximum displacement, of 300µm at 1Hz. Key words: micromachining, microactuator, TiNi, Shape memory alloy. 3-D microstructurt. © 1997, The Institute of Electrical Engineers of Japan. All rights reserved.