M. Tomozawa, H. Y. Kim, University of Tsukuba, Ibaraki, Japan; S. Miyazaki, University of Tsukuba, Tsukuba, Japan
Diaphragm-type microactuators utilizing Ti-Ni-Cu SMA thin films were fabricated and their actuation behavior was investigated. The fabrication procedure is as follows. A Ti-38.0Ni-10.0Cu SMA thin film with the thickness of 1.5μm was deposited onto a SiO2/Si substrate by using a r.f. magnetron sputtering apparatus. The thin films on the substrates were heat-treated at 873, 923, 973 and 1023 K for 0.6ks, respectively. Diaphragm-type microactuators were fabricated by using the conventional Si micromachining technique. The transformation temperature of the microactuators increased from 329 to 351 K with increasing heat-treatment temperature from 873 to 973 K, then decreased. The transformation temperature hysteresis decreased from 16.5 to 5.6 K with increasing heat-treatment temperature from 873 to 973 K, then slightly increased. Actuation stroke decreased with increasing heat-treatment temperature. The dynamic actuation properties of the microactuator heat-treated at 973 K, which showed the highest transformation temperature with the lowest transformation temperature hysteresis, were investigated. The microactuator repeatedly operated by applying pulsating current with various frequencies and amplitudes. The microactuator operated at a working frequency of 70 Hz without decrease of the actuation stroke. In addition, the microactuator operated even at frequency of 100 Hz.
Summary: Ti-Ni-Cu shape memory alloy (SMA) thin films are promising candidates for high-speed microactuator due to their narrow transformation temperature hysteresis. In this study, microactuator utilizing Ti-Ni-Cu SMA thin films were fabricated and their actuation properties were characterized.
