Micro and Nanosystems, KTH Royal Institute of Technology, Osquldas väg 10, Floor 5, Stockholm SE-10044, Sweden.
Adv Colloid Interface Sci. 2013 Nov;199-200:78-94. doi: 10.1016/j.cis.2013.06.006. Epub 2013 Jul 10.
Today, despite the growing interest in nanofluidics, the descriptions of the many complex physical phenomena occurring at this scale remain scattered in the literature. Due to the additional complexity encountered when considering electrostatic nanofluidic gating, it is important to regroup several relevant theories and discuss them with regard to this application. In this work, we present a theoretical study of electrostatically gated phenomena and propose a model for the electrostatic gating of ion and molecular transport in nanochannels. In addition to the classical electrokinetic equations, that are reviewed in this work, several relevant phenomena are considered and combined to describe gating effects on nanofluidic properties more accurately. Dynamic surface charging is accounted for and is shown to be an essential element for electrostatic gating. The autoprotolysis of water is also considered to allow for accurate computing of the surface charge. Modifications of the Nernst-Planck equations are considered for more accurate computing of the concentration profiles at higher surface potentials by accounting for ion crowding near charge walls. The sensitivity of several parameters to the electric field and ion crowding is also studied. Each of these models is described separately before their implementation in a finite element model. The model is verified against previous experimental work. Finally, the model is used to simulate the tuning of the ionic current through the nanochannel via electrostatic gating. The influence of the additional models on these results is discussed. Guidelines for potentially better gating efficiencies are finally proposed.
尽管人们对纳流控越来越感兴趣，但对这一尺度下发生的许多复杂物理现象的描述仍然分散在文献中。由于在考虑静电纳流控门时遇到了额外的复杂性，因此有必要重新组合几个相关理论，并针对该应用进行讨论。在这项工作中，我们对静电门控现象进行了理论研究，并提出了一种用于纳米通道中离子和分子输运的静电门控模型。除了本文中回顾的经典电动方程外，还考虑了几个相关现象，并将它们结合起来，以更准确地描述门控效应对纳流控性质的影响。动态表面充电被考虑在内，并且被证明是静电门控的一个基本要素。水的自离解也被考虑在内，以允许更准确地计算表面电荷。为了更准确地计算更高表面势下的浓度分布，考虑了对 Nernst-Planck 方程的修正，以考虑到电荷壁附近的离子拥挤现象。还研究了几个参数对电场和离子拥挤的敏感性。在将模型实现到有限元模型之前，分别描述了每个模型。模型与先前的实验工作进行了验证。最后，该模型用于模拟通过静电门控来调整纳米通道中的离子电流。讨论了附加模型对这些结果的影响。最后提出了提高门控效率的潜在建议。
