Development of Microactuators Possessing High Power and Large Actuation Utilizing Ti-Ni Sputter-deposited Shape Memory Alloy Films

点击翻译按钮获取中文摘要

Ti-Ni shape memory alloy thin films are expected to be applied for microactuators due to the great advantages such as large shape recovery force and strain. In this research, Ti-Ni thin films were deposited on Si substrates with SiO2 surface by using the radio frequency magnetron sputtering method. Diaphragm microactuators were fabricated by applying the Si photoetching method, and heat-treatment was carried out in order to acquire shape memory effects. The shape of the diaphragm was square with the width of 560 micron meters. The Ti-Ni diaphragm was convex in the martensite phase and flat in the parent phase : the shape change occurred repeatedly by cooling and heating. In order to evaluate the dynamic motion of the diaphragm microactuator, a three-dimensional shape analysis was performed with varying experimental parameters such as frequency and current. It was found that the displacement of the Ti-Ni binary alloy microactuator was changed by changing the current and/or the frequency … More .A Ti-Ni microactuator revealed an effective cyclic response below a cyclic frequency of several tens Hz. In order to improve the cyclic response, Pd was added to make Ti-Ni-Pd thin films for microactuators, because Pd addition increases the Ms temperature so that a higher cooling rate can be expected at a higher temperature. The maximum Ms temperature of the Ti-Ni was 340K, while that of the Ti-Ni-Pd was 420K which is 80K higher than that of the binary alloy. A Ti-Ni-Pd microactuator revealed effective actuation at 80 Hz. Cu was also added to make Ti-Ni-Cu thin films, which posses a narrower transformation temperature hysteresis and a smaller transformation strain when compared with those of the Ti-Ni films : the hysteresis of the former is only one third of that of the latter. An effective actuation was observed in the Ti-Ni-Cu microactuator even at 100 Hz. A narrow transformation temperature hysteresis can be also expected by using the R-phase transformation. A Ti-Ni microactuator showed an effective motion even at 125 Hz. With the results mentioned above, high speed and powerful microactuators can be fabricated for variety of purposes in the near future. Less