Department of Mechanical Science and Engineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
J Colloid Interface Sci. 2012 Oct 15;384(1):162-71. doi: 10.1016/j.jcis.2012.06.004. Epub 2012 Jun 15.
The integration of a microchannel with a nanochannel is known to exhibit anomalous nonlinear current-voltage characteristics. In this paper, we perform detailed numerical simulations considering a 2-D nonlinear ion transport model, to capture and explain the underlying physics behind the limiting resistance and the overlimiting current regions, observed predominantly in a highly ion-selective nanochannel. We attribute the overlimiting current characteristics to the redistribution of the space charges resulting in an anomalous enhancement in the ionic concentration of the electrolyte in the induced space charge region, beyond a critical voltage. The overlimiting current with constant conductivity is predicted even without considering the effects of fluidic nonlinearities. We extend our study and report anomalous rectification effects, resulting in an enhancement of current in the non-ohmic region, under the application of combined AC and DC electric fields. The necessary criteria to observe these enhancements and some useful scaling relations are discussed.
微通道与纳通道的集成被认为表现出异常的非线性电流-电压特性。在本文中，我们进行了详细的数值模拟，考虑了一个 2-D 非线性离子输运模型，以捕捉和解释主要在高度离子选择性纳通道中观察到的限制电阻和过限电流区域背后的物理原理。我们将过限电流特性归因于空间电荷的再分布，导致在临界电压之后，感应空间电荷区域中的电解质离子浓度异常增强。即使不考虑流态非线性的影响，我们也预测了具有恒定电导率的过限电流。我们扩展了我们的研究，并报告了异常整流效应，即在施加交流和直流电场时，非欧姆区域的电流增强。讨论了观察这些增强的必要条件和一些有用的比例关系。
