Breaking electrolyte symmetry in induced-charge electro-osmosis
Breaking electrolyte symmetry in induced-charge electro-osmosis
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DOI：
10.1017/jfm.2020.754
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发表时间：
2020-12-25
影响因子：
3.7
通讯作者：
Balu, Bhavya
中科院分区：
文献类型：
--
作者：
Khair, Aditya S.;Balu, Bhavya
分析了在阴阳离子扩散系数不等的二元电解质中，在无限长、理想极化、不带电圆柱体周围施加交变电场所引起的诱导电荷电渗流（ICEO）。薄德拜层和弱场近似被调用来计算时间平均的，或整流，四极ICEO绕柱流。离子扩散系数的不相等导致德拜层外的电中性体电解质中的瞬态离子浓度梯度，或浓度极化。因此，体内的电势是非谐波的。此外，浓差极化改变了圆柱体表面的电渗滑移，并在本体中产生体积力，这两者都影响整流ICEO流。对于不同的离子扩散系数比的整流流的强度的预测与现有的实验数据是合理的协议。我们的工作强调，在离子扩散系数的不平等-所有电解质在一定程度上拥有-是一个重要的因素，在模拟ICEO流量。
Induced-charge electro-osmotic (ICEO) flow caused by an alternating electric field applied around an infinitely long, ideally polarizable, uncharged circular cylinder in a binary electrolyte with unequal cation and anion diffusion coefficients is analysed. The thin-Debye-layer and weak-field approximations are invoked to compute the time-averaged, or rectified, quadrupolar ICEO flow around the cylinder. The inequality of ionic diffusion coefficients leads to transient ion concentration gradients, or concentration polarization, in the electroneutral bulk electrolyte outside the Debye layer. Consequently, the electric potential in the bulk is non-harmonic. Further, the concentration polarization alters the electro-osmotic slip at the surface of the cylinder and generates body forces in the bulk, both of which affect the rectified ICEO flow. Predictions for the strength of the rectified flow for varying ratio of ionic diffusion coefficients are in reasonable agreement with available experimental data. Our work highlights that an inequality in ionic diffusion coefficients - which all electrolytes possess to some extent - is an important factor in modelling ICEO flows.