Development of Microactuators Driven by Liquid Crystals(5th Report, Numerical Simulation of Driving a Plate)

Abstract

We have proposed a one-dimensional simple model for predicting the performance of liquid crystal actuators by combining the motion of the upper plate of a liquid crystal cell and the flow of a liquid crystal. Comparison of the motion of the plate between the numerical predictions and the experimental results reported in the previous paper shows that the proposed model is useful to predict qualitatively the motion of the upper plate. By using the model, we have studied the rotation of the molecules and the velocity profiles between two plates. As a result, it is clarified that when the electric field is released, the molecule in the middle region between two plates returns to the initial angle completely at 1 Hz of the frequency of the applied voltage, it does not return to the initial angle but it takes approximately 40 deg at 10 Hz, and it oscillates around 90 deg with a small amplitude at 100 Hz. While its profile is S shaped in lower 10 Hz frequency, the induced velocity shows a double-S shaped profile in higher 20 Hz frequency. Such the peculiar velocity profile stems from the so-called kickback effect. The maximum shear stress acting on a wall reaches 20 Pa in frequency of 20 - 30 Hz. This frequency range is coincident with the frequency at which the double-S shaped profile begins to occur.