Convective Liquid Crystal Membranes

本研究项目探讨液晶作为膜屏障的独特性质，用于电场增强流体混合物的分离。这种材料是部分有序相的有机分子。电场作用于LC可以影响晶体内部的空间秩序，最显著的影响是各种电流体动力学（EHD）不稳定性和各向异性。在电子存在的情况下，这种各向异性产生电流聚焦和空间电荷积累，从而导致电体力和LC的流动。通过适当的参数选择，该流可以增强电荷蓄能器的正反馈形式，从而产生不稳定性。此外，动态交流场的结果是对亚微米尺度的混沌湍流的一系列分岔。EHD诱导的不稳定性可以用来制造具有电压控制磁导率的结构。薄膜屏障的渗透是通过漫射通量发生的，当受到电场的作用时，LC层的渗透性会产生可控的大幅度增加。对于不同溶解度的混合物，高渗透EHD状态可以成为分离过程中有效的选择性膜。此外，由于通过屏障的传输增强，该技术可以用作“磁导率开关”，为传感元件提供快速、干净的信号，用于按需采样和工艺流分析。

This research project explores the unique properties of liquid crystals (LCs) as membrane barriers for electrical field- enhanced separation of fluid mixtures. Such materials are organic molecules which form partially ordered phases. Application of an electric field to the LC can influences spatial order within the crystal, the most dramatic effect being a variety of electrohydrodynamic (EHD) instabilities and anisotropy. In the presence of an electron this anisotropy produces current focus and space charge accumulation, which in turn leads to electric body forces and flow of the LC. With appropriate parameter selection this flow can enhance the charge accumulator, a form of positive feedback, thus producing the instability. Moreover, the result with a dynamic AC field is a series of bifurcations to chaotic turbulent flow as sub-micron dimensions. The EHD induced instability can be used to make structures exhibiting voltage controlled permeability. Permeation across the membrane barrier occurs by diffuse flux which when subjected to the electric force produces a large controllable increase in the permeability of the LC layer. For mixtures with different solubilities, the high permeability EHD state can become an effective and selective membrane for separation processes. In addition, because of the enhanced transport induced across the barrier, the technique can be used as a "permeability switch" for providing a rapid, clean signal to a sensing element for on-demand sampling and analysis of process streams.