Particle distribution and velocity in electrokinetically induced banding
Particle distribution and velocity in electrokinetically induced banding
复制标题
动电感应条带中的颗粒分布和速度
DOI：
10.1007/s10404-019-2227-9
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发表时间：
2019
影响因子：
2.8
通讯作者：
M. Yoda
中科院分区：
文献类型：
--
作者：
M. Rossi;A. Marin;N. Cevheri;C. J. Kähler;M. Yoda
当电渗透流与泊泽维尔流相结合时，胶体颗粒可能会被玻璃微通道的壁面排斥或吸引。在一定条件下，粒子在壁面附近聚集后聚集成条带（Cevheri and Yoda in Lab Chip 14(8):1391 - 1394,2014）。这些现象背后的基本物理机制仍然不清楚，到目前为止，只能在墙内进行测量。在这项工作中，我们应用了一种三维粒子跟踪技术，散光粒子跟踪测速，来测量整个微通道深度上粒子的浓度和速度分布。实验表明，颗粒在靠近底壁和顶壁的地方集中时，颗粒在体中被耗尽，这种颗粒的再分布强烈地依赖于体颗粒的浓度。结果表明，在颗粒几乎不移动的区域形成条带，并且它们的体积分数相对于原始体积分数至少增加了一个数量级。我们的研究结果表明，颗粒聚集和带状形成可能是由体内产生的力触发的，因为带状和颗粒积聚至少延伸到通道内一些地方，或者由于壁面相互作用而超出表面力范围的长度尺度。
Colloidal particles may be repelled from/attracted to the walls of glass micro-channels when an electro-osmotic flow is combined with a Poiseuille flow. Under certain conditions, the particles assemble into bands after accumulating near the walls (Cevheri and Yoda in Lab Chip 14(8):1391–1394, 2014). The fundamental physical mechanisms behind these phenomena remain unclear and up to now only measurements withinof the walls have been available. In this work, we applied a 3D particle-tracking technique, astigmatism particle tracking velocimetry, to measure the concentration and velocity distribution of particles across the depth of the entire micro-channel. The experiments show that the particles are depleted in the bulk as they become concentrated near the bottom and top walls and this particle redistribution depends strongly upon the bulk particle concentration. The results suggest that bands form in a region where particles are practically immobile and their volume fraction increases at least an order of magnitude with respect to the original volume fraction. Our results suggest that particle accumulation and band formation near the walls may be triggered by forces generated in the bulk since the banding and particle accumulation extends at least a fewinto the channel, or at length scales beyond the range of surface forces due to wall interactions.
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