Development of micro-actuators using liquid crystals

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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.