Development of micro-actuators using liquid crystals

当一个液晶被填充在两个平行的平板之间，并对液晶施加电压，使所有分子的方向与平板平行时，除了壁面附近的分子围绕它们的重心旋转，并重新定向到垂直于平板的方向。结果在板间产生流动。该原理的应用导致了新型执行机构的发展，这些执行机构与过去的执行机构完全不同；也就是说，由于液晶表现为液体，这种新型执行器具有以下优点；原理很简单。任何形状都可以接受。原则上，缩小到几十纳米级是可能的，在这种情况下连续介质力学是有效的。在本研究中，我们以平板滑块作为执行器，并对作用在平板上的剪切应力进行了数值估计。结果表明，剪切应力的最大值为1 mPa。接下来，我们做了一个玻璃板的运动实验，玻璃板被放置在一个放置在固定板上的液晶上。玻璃板面积为10 mm×10 mm，厚度为0.7 mm，质量为0.18 g。两块板间距为300μm。当对液晶施加12v直流电压时，通过显微镜观察到上玻璃板在15秒内移动约38μm。最后，对两个平行板间的速度分布进行了可视化实验。因此，当扭转角为0度时，速度曲线是一个字母“S”，相对于电池的中心平面是反对称的。施加电压时，速度的绝对值很大，但曲线的形状与电压无关。另一方面，当扭转角为180°时，感应速度是单向的，并在胞体的中心平面处达到最大。

When a liquid crystal is filled between two parallel plates and a voltage is applied to the liquid crystal with all molecules orienting parallel to the plates, the molecules except for wall vicinity rotate around their center of gravity and reorient to the direction perpendicular to the plates. Resultantly a flow is induced between plates. Application of the principle leads to development of new actuators which have completely different mechanism from that in a past ; that is, because a liquid crystal behaves as a liquid, the new actuators have the following advantages ;1.the mechanism is very simple2.any shape is accepted3.in principle, downsizing is possible to several decades of nano order, in which the continuum mechanics is valid.In this study, we have taken a flat plate slider as an actuator, and have numerically estimated the shear stress acting on the plate. It is found that the maximum value of the shear stress is 1 mPa. Next, we have made an experiment for movement of a glass plate which is placed on a liquid crystal dropped on a fixed plate. The glass plate is 10 mm×10 mm in area and 0.7 mm in thickness, and its mass is 0.18 g. The gap between two plates is 300μm. When DC voltage of 12 V is applied on the liquid crystal, it is observed through microscope that the upper glass plate was moved by about 38μm for 15 seconds. Finally, we have made a visualization experiment for velocity profile between two parallel plates. As a result, the velocity profile is a letter of"S", and anti-symmetric with respect to the center plane of the cell when the twist angle is 0 deg. The absolute value of the velocity is large with the applied voltage, but the shape of the profile is independent of the voltage. For the twist angle of 180 deg, on the other hand, it is found that the induced velocity is unidirectional and becomes maximum at the center plane of the cell.