Wu Zhemin, Gao Yandong, Li Dongqing
Department of Mechanical Engineering, Vanderbilt University, Vanderbilt Place, Nashville, TN, USA.
Electrophoresis. 2009 Mar;30(5):773-81. doi: 10.1002/elps.200800381.
The induced-charge electrophoretic (ICEP) motion of ideally polarizable particles in a microchannel is numerically studied in this paper. A complete 3-D multi-physics model is set up to simulate the transient ICEP motion of spherical ideally polarizable particles in a microchannel. The study shows that a non-uniform distribution of induced surface charge occurs when an ideally polarizable particle is immersed in an externally applied electric field, resulting in a varying slipping (EOF) velocity along the particle's surface and hence producing micro vortexes in the liquid. The numerical results verify that the steady-state ICEP velocity of an ideally polarizable particle does not differ from the electrophoretic velocity of a non-conducting particle, although the flow field near the particle does. A strong wall-repelling effect of ICEP is found when the polarizable particle is placed close to the channel wall. This is due to the lifting effect generated from the interaction between the induced micro vortexes and the channel wall and depends on the electric field and the particle size. The wall effects on ICEP motion can be used for focusing particles and for separation of particle by density.
本文对微通道中理想极化颗粒的感应电荷电泳（ICEP）运动进行了数值研究。建立了一个完整的三维多物理场模型，以模拟微通道中球形理想极化颗粒的瞬态ICEP运动。研究表明，当理想极化颗粒浸入外加电场中时，会产生感应表面电荷的非均匀分布，导致沿颗粒表面的滑移（电渗流）速度变化，从而在液体中产生微涡旋。数值结果验证了理想极化颗粒的稳态ICEP速度与非导电颗粒的电泳速度并无差异，尽管颗粒附近的流场有所不同。当可极化颗粒靠近通道壁放置时，发现ICEP具有很强的壁排斥效应。这是由于感应微涡旋与通道壁之间相互作用产生的升力效应，且取决于电场和颗粒大小。ICEP运动的壁效应可用于颗粒聚焦和按密度分离颗粒。
