Fundamental Study on New Micro Fluidic Drive Method Based on Liquid Crystalline Backflow

Abstract: In this study, we propose a one-dimensional simple model for predicting the performance of the new micro fluidic drive and then we have a research of the control method based on liquid crystalline backflow by combining the motion of the upper plate of a liquid crystal cell and the flow of a liquid crystal. Comparison of the numerical predictions and the experimental results shows that the proposed model is useful to predict qualitatively the motion the upper plate. The drive efficiency is affected by applied voltage, the frequency, the duty ratio and the gap of the cell. The ideal drive quality can be achieved when the rotation range of the molecules at the center of the cell is controlled within 50-80°

Transient behaviors of molecular orientation field of nematic liquid crystal under shear flows between concentric cylinders

Transient behaviors of molecular orientation field of nematic liquid crystal (4-n-4’-octylcyanobiphenyl) under shear flows between concentric cylinders have been numerically investigated using the Leslie-Ericksen continuum theory in which the molecular orientation is represented with a unit vector, called the director. As well as the rotation speed of an inner cylinder, the director anchoring conditions at the inner and outer cylinders are chosen as simulation parameters to obtain four different cases of director initial profiles, which are homeotropic, hybrid, planar, and twist cases. After the imposition of the shear flow, the director start rotating within the shear plane, increasing the curvature energy of the director field. When the energy exceeds a certain critical value, the director start escaping from the shear plane, called the out-of-plane behavior. Because the escaping direction (i.e., either +z or -z directions) is the stochastic choice, the director field is randomly separated into the positive and negative out-of-plane regions. Then, the spatially distributed two out-of-plane regions are transformed into line defect structures. The spatial patterns of the out-of-plane regions and the line defect structures strongly depends on the director anchoring conditions, and no patterns are found for the twist case. The evolutions of torques of the inner cylinder is also estimated from the simulation results for four cases, and the oscillatory behavior of the torque is found for the homeotropic case