Experimental observations of bands of suspended colloidal particles subject to shear flow and steady electric field
Experimental observations of bands of suspended colloidal particles subject to shear flow and steady electric field
复制标题
剪切流和稳定电场作用下悬浮胶体颗粒带的实验观察
DOI：
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发表时间：
2018
影响因子：
2.8
通讯作者：
M. Yoda
中科院分区：
文献类型：
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作者：
A. Yee;M. Yoda
操纵悬浮的胶体粒子在微通道中流动是微流体学和纳米技术的研究方向。然而，流动本身可以通过壁向“升力”影响这些悬浮颗粒的动力学。通过~ 30 μm深的波塞维尔流和EO流，定量研究了受直流电场作用的剪切流中悬浮颗粒的近壁动力学。当两股气流方向相反时，粒子就会被壁面吸引。然后，它们组装成非常高的纵横比结构，或集中的流向“带”，高于最小电场大小，并且似乎具有最小的近壁剪切速率。这些条带只存在于靠近壁面的几微米处，并且在横流方向上大致是周期性的，尽管沿着这个方向没有外力。本文介绍了聚苯乙烯颗粒稀悬液在不同粒径、浓度和zeta电位范围内形成第一个带的时间和在~ 200 μm范围内的带数的实验观察和量纲分析。据我们所知，没有理论解释能带组装，但本文提出的结果表明，它发生在不同的颗粒和流动参数的大范围内。
Manipulating suspended colloidal particles flowing through a microchannel is of interest in microfluidics and nanotechnology. However, the flow itself can affect the dynamics of these suspended particles via wall-normal “lift” forces. The near-wall dynamics of particles suspended in shear flow and subject to a dc electric field was quantified in combined Poiseuille and EO flow through a ~ 30 μm deep channel. When the two flows are in opposite directions, the particles are attracted to the wall. They then assemble into very high aspect ratio structures, or concentrated streamwise “bands,” above a minimum electric field magnitude, and, it appears, a minimum near-wall shear rate. These bands only exist over the few micrometers next to the wall and are roughly periodic in the cross-stream direction, although there are no external forces along this direction. Experimental observations and dimensional analysis of the time for the first band to form and the number of bands over a field of view of ~ 200 μm are presented for dilute suspensions of polystyrene particles over a range of particle radii, concentrations, and zeta potentials. To our knowledge, there is no theoretical explanation for band assembly, but the results presented here demonstrate that it occurs over a wide range of different particle and flow parameters.