Liquid-crystal-enabled electrophoresis of spheres in a nematic medium with negative dielectric anisotropy
Liquid-crystal-enabled electrophoresis of spheres in a nematic medium with negative dielectric anisotropy
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DOI：
10.1098/rsta.2012.0255
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发表时间：
2013-04-13
期刊：
影响因子：
5
通讯作者：
Lavrentovich, Oleg D.
中科院分区：
文献类型：
--
作者：
Lazo, Israel;Lavrentovich, Oleg D.
我们描述了在具有负介电各向异性的均匀排列的向列相介质中球形介质颗粒的电泳性。使液晶(LC)垂直于其表面的球形粒子在均匀的直流电或交流电的作用下运动。电场不会使远离球面的LC指向矢发生扭曲。向列相LC中的电泳谱显示了速度对场依赖的两种类型的非线性。平行于外加电场的速度分量随场强呈线性增长，但当电场足够高时，速度分量也表现出三次关系。最有趣的是第二种类型的非线性电泳法，它使球体垂直于外加电场运动。速度的这个垂直分量与场的平方成正比。这种效应只存在于液晶中，当材料熔化到各向同性流体中时，该效应就消失了。二次效应是由指向器扭曲在球体周围的偶极对称性引起的，被归类为LC使能电泳(LCEEP)。LCEEP中粒子的非线性电泳迁移率为设计微流控和光流控应用中的粒子三维轨迹提供了丰富的控制参数。
We describe electrophoresis of spherical dielectric particles in a uniformly aligned nematic medium with a negative dielectric anisotropy. A spherical particle that orients the liquid crystal (LC) perpendicularly to its surface moves under the application of a uniform direct current or alternating current electric field. The electric field causes no distortions of the LC director far away from the sphere. Electrophoresis in the nematic LC shows two types of nonlinearity in the velocity versus field dependence. The velocity component parallel to the applied electric field grows linearly with the field, but when the field is high enough, it also shows a cubic dependence. The most interesting is the second type of nonlinear electrophoresis that causes the sphere to move perpendicularly to the applied field. This perpendicular component of velocity is proportional to the square of the field. The effect exists only in an LC and disappears when the material is melted into an isotropic fluid. The quadratic effect is caused by the dipolar symmetry of director distortions around the sphere and is classified as an LC-enabled electrophoresis (LCEEP). The nonlinear electrophoretic mobility of particles in LCEEP offers a rich variety of control parameters to design three-dimensional trajectories of particles for microfluidic and optofluidic applications.