A Simulation Analysis of Nanofluidic Ion Current Rectification Using a Metal-Dielectric Janus Nanopore Driven by Induced-Charge Electrokinetic Phenomena
A Simulation Analysis of Nanofluidic Ion Current Rectification Using a Metal-Dielectric Janus Nanopore Driven by Induced-Charge Electrokinetic Phenomena
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感应电荷动电现象驱动的金属电介质 Janus 纳米孔纳流离子电流整流仿真分析
DOI：
10.3390/mi11060542
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发表时间：
2020-05
期刊：
影响因子：
3.4
通讯作者：
Qisheng Wu
中科院分区：
文献类型：
--
作者：
Weiyu Liu;Yongjun Sun;Hui Yan;Yukun Ren;Chunlei Song;Qisheng Wu
本文提出了一种在金属-介质Janus纳米孔中产生可调表面电荷的独特机制，用于纳米流体离子二极管的开发，其中不带电的金属纳米通道与固定表面电荷的介质纳米孔串联。在位于非对称Janus纳米孔两侧的两个探针提供的外电场的响应下，纳米通道的金属部分发生电化学极化，因此在靠近导电壁的大块电解质中正离子和负离子浓度富集的区域之间形成了一个关键结。在带负电荷的电介质纳米孔内，电场诱导的双极诱导双层和充满阳离子的天然单极双层的共同作用导致了电压可控的异质体积电荷分布。电场诱导的反离子沿纳米孔长度方向的电化学传输产生了一个离子富集/耗尽的内部区域，从而增强/抑制了Janus纳米孔内产生的电流，从而实现了纳米流体离子二极管的反向工作状态。建立了基于连续介质力学的数学模型，研究了Janus纳米通道引起充分离子电流整流的可行性，我们发现只有孔径和德拜长度之间的良好匹配才能在实际应用中产生可靠的整流功能。这种整流效果让人想起典型的双极膜，但由于导电端诱导电荷的电动极化，由于电压控制的性质，这种整流效果更加灵活，这可能有助于渗透能量转换，其中由于盐浓度的差异而出现电流。我们对复合金属-介电离子选择介质的理论论证为利用感应电荷电动力学现象构建灵活的片上平台提供了有用的指导，以实现高度自由的离子电流控制。
We propose herein a unique mechanism of generating tunable surface charges in a metal-dielectric Janus nanopore for the development of nanofluidic ion diode, wherein an uncharged metallic nanochannel is in serial connection with a dielectric nanopore of fixed surface charge. In response to an external electric field supplied by two probes located on both sides of the asymmetric Janus nanopore, the metallic portion of the nanochannel is electrochemically polarized, so that a critical junction is formed between regions with an enriched concentration of positive and negative ions in the bulk electrolyte adjacent to the conducting wall. The combined action of the field-induced bipolar induced double layer and the native unipolar double layer full of cations within the negatively-charged dielectric nanopore leads to a voltage-controllable heterogenous volumetric charge distribution. The electrochemical transport of field-induced counterions along the nanopore length direction creates an internal zone of ion enrichment/depletion, and thereby enhancement/suppression of the resulting electric current inside the Janus nanopore for reverse working status of the nanofluidic ion diode. A mathematical model based upon continuum mechanics is established to study the feasibility of the Janus nanochannel in causing sufficient ion current rectification, and we find that only a good matching between pore diameter and Debye length is able to result in a reliable rectifying functionality for practical applications. This rectification effect is reminiscent of the typical bipolar membrane, but much more flexible on account of the nature of a voltage-based control due to induced-charge electrokinetic polarization of the conducting end, which may hold promise for osmotic energy conversion wherein an electric current appears due to a difference in salt concentration. Our theoretical demonstration of a composite metal-dielectric ion-selective medium provides useful guidelines for construction of flexible on-chip platforms utilizing induced-charge electrokinetic phenomena for a high degree of freedom ion current control.
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