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

Ti-Ni形状记忆合金薄膜具有较大的形状恢复力和应变等优点，有望应用于微致动器。在本研究中，采用射频磁控溅射的方法将Ti-Ni薄膜沉积在具有SiO2表面的Si衬底上。采用硅光刻法制备膜片微致动器，并对其进行热处理以获得形状记忆效应。膜片的形状为方形，宽度为560微米。Ti-Ni膜片在马氏体相中呈凸形，在母相中呈扁平状，在冷却和加热过程中反复发生形状变化。为了评价膜片微动器的动态运动特性，对膜片微动器在不同频率和电流等实验参数下进行了三维形状分析。研究发现，通过改变电流和/或频率，可以改变钛镍二元合金微致动器的位移。Ti-Ni微致动器在低于几十Hz的循环频率下具有有效的循环响应。为了改善循环响应，在微致动器中加入Pd来制作Ti-Ni-Pd薄膜，因为Pd的加入提高了Ms温度，因此在更高的温度下可以预期更高的冷却速率。Ti-Ni合金的最高Ms温度为340K， Ti-Ni- pd合金的最高Ms温度为420K，比二元合金高80K。Ti-Ni-Pd微致动器显示在80 Hz下有效致动。加入Cu制备Ti-Ni-Cu薄膜，与Ti-Ni薄膜相比，Ti-Ni-Cu薄膜具有更窄的转变温度滞后和更小的转变应变，前者的滞后仅为后者的三分之一。即使在100 Hz的频率下，Ti-Ni-Cu微致动器也能有效地致动。采用r相变法，还可以得到较窄的相变温度滞后。Ti-Ni微致动器即使在125 Hz下也显示出有效的运动。基于上述结果，在不久的将来，高速和强大的微致动器可以用于各种用途。少

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