Back-Flow of Nematic Liquid Crystals and Its Application to Liquid Crystalline Microactuators

摘要

With the aim of the development of liquid crystalline microactuators, the numerical and experimental studies of the back-flow effect of nematic liquid crystals have been performed. The Leslie-Ericksen continuum theory is used to simulate the back-flow of a nematic liquid crystal, 4-n-pentyl-4-cyanobiphenyl (5CB), between parallel plates. The lower plate is fixed, and the upper plate can move freely. From the results, it is found that the translational movement of the upper plate occurs owing to the shear stress arisen from the back-flow, when an electric field is imposed between the upper and lower plates. By applying the pulsed voltage, continuous movement of the upper plate is able to be achieved. The effects of the applied voltage, frequency of the pulse, gap width, and the surface molecular anchoring condition on the driving efficiency of the actuators are thoroughly investigated to obtain the optimal condition for the actuators. For example, the averaged driven speed of the upper plate increases with increase of the frequency of the pulse and decrease of the gap width. These results are ascertained in the experiment, in which the translational movement of the upper glass plate is observed under a microscope when pulsed voltage is applied between the glass plates. Finally, we propose several types of liquid crystalline actuators, such as sliders and motors.