Mass transfer and flow in electrically charged micro- and nanochannels
Mass transfer and flow in electrically charged micro- and nanochannels
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DOI：
10.1021/ac011198o
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发表时间：
2002-05-01
影响因子：
7.4
通讯作者：
Hansford, D
中科院分区：
文献类型：
--
作者：
Conlisk, AT;McFerran, J;Hansford, D
在这项工作中，由于电场的存在下，在矩形通道中的流体流动和质量传递的检查。我们考虑水或另一种中性溶剂与盐化合物（如氯化钠）的混合物，其中离子物种完全解离。结果产生的情况下，其中的通道高度是远远大于双电层（EDL）（微通道）和通道的高度是的顺序的EDL（纳米通道）的宽度的情况下。对称和非对称的速度，潜在的，和摩尔分数的分布被认为是不同于以前的工作在这个问题上。在小电解质浓度下，双电层的Debeye-Huckel图像恢复;在较大浓度下，双电层的Gouy-Chapman图像自然出现。这里给出的数值结果与奇异摄动分析的解析解一致，这是有效的通道高度增加。在对称的情况下，这样诱导的电渗流，速度场和电位是相似的。在对应于不同壁势的非对称情况下，速度和势可以大不相同。流体被假定为一个连续体的行为，并观察到的体积流率随通道高度线性变化的电驱动流，相反，压力驱动流，高度立方变化。这意味着需要非常大的压降来驱动小通道中的流动。然而，可以在非常低的驱动电压下获得有用的体积流率。
In this work, the fluid flow and mass transfer due to the presence of an electric field in a rectangular channel is examined. We consider a mixture of water or another neutral solvent and a salt compound, such as sodium chloride, for which the ionic species are entirely dissociated. Results are produced for the case in which the channel height is much greater than the electric double layer (EDL) (microchannel) and for the case in which the channel height is of the order of the width of the EDL (nanochannel). Both symmetric and nonsymmetric velocity, potential, and mole fraction distributions are considered, unlike previous work on this problem. At small electrolyte concentrations, the Debeye-Huckel picture of the electric double layer is recovered; at larger concentrations, the Gouy-Chapman picture of the electric double emerges naturally. The numerical results presented here agree with analytical solutions of a singular perturbation analysis, which is valid as the channel height increases. In the symmetric case for the electroosmotic flow so induced, the velocity field and the potential are similar. In the asymmetric case corresponding to different wall potentials, the velocity and potential can be vastly different. The fluid is assumed to behave as a continuum, and the volume flow rate is observed to vary linearly with channel height for electrically driven flow, in contrast to pressure-driven flow, which varies as height cubed. This means that very large pressure drops are required to drive flows in small channels. However, useful volume flow rates may be obtained at a very low driving voltage.