Current monitoring in nanochannels
Current monitoring in nanochannels
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DOI：
10.1007/s10404-022-02589-1
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发表时间：
2022-10
影响因子：
2.8
通讯作者：
Siyang Xiao;Zachary Wollman;Q. Xie;Chuanhua Duan
中科院分区：
文献类型：
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作者：
Siyang Xiao;Zachary Wollman;Q. Xie;Chuanhua Duan
电流监测（CM）是一种间接的实验方法，用于表征受限通道中的表面zeta电位。虽然这种方法已成功地用于微通道，其有效性在纳米流体装置仍然难以捉摸，由于不可忽略的影响，从相对厚的双电层和大的表面传导。在这项工作中，我们数值研究了在各种条件下，包括不同的离子浓度，离子扩散率，表面电荷密度，和通道高度的一价二元盐溶液填充的纳米通道的电流监测及其准确性。结果表明，随着双电层厚度的增加，电流监测法测得的zeta电位与实际值有一定的偏差，当德拜长度大于半沟道高度的15%时，zeta电位达到零。然而，对于具有较小德拜长度的情况，偏差的大小可以通过简单的表达式精确地预测，该表达式仅与德拜长度与纳米通道高度和平均离子扩散率的比率相关，即使当表面传导在中等范围内时。我们的观察结果可以解释的去离子冲击波效应，这个新的表达式提供了准确测量zeta电位在纳米通道使用电流监测，这将导致更好地控制各种nanofluidic应用的电动流动的指导方针。
Current monitoring (CM) is an indirect experimental method for characterizing surface zeta potentials in confined channels. Although this method has been successfully used in microchannels, its validity in nanofluidic devices has remained elusive due to non-negligible effects from relatively thick electrical double layers and large surface conduction. In this work, we numerically investigated current monitoring and its accuracy in nanochannels filled with the monovalent binary salt solution under various conditions, including different ionic concentrations, ion diffusivities, surface charge densities, and channel heights. Our results show that the zeta potential measured by current monitoring deviates from the actual value as the electrical double layer becomes thick, reaching zero when the Debye length is more than 15% of the half channel height. However, for cases with a smaller Debye length, the magnitude of deviation can be precisely predicted by a simple expression, which is only related to the ratio of the Debye length to the nanochannel height and the average ion diffusivity even when the surface conduction is in the moderate range. Our observations can be explained by the deionization shock wave effect, and this new expression provides guidelines for accurately measuring zeta potentials in nanochannels using current monitoring, which would lead to better control of electrokinetic flows for various nanofluidic applications.