离子扩散纳米流体通道的原子尺度设计与三维模拟
Atomic Scale Design and Three-Dimensional Simulation of Ionic Diffusive Nanofluidic Channels
摘要：
纳米技术的最新进展导致了纳米流体的快速发展，纳米流体已被确立为用于各种应用的可靠手段，包括分子分离、检测、结晶和生物合成。虽然原子和分子水平的考虑是实验设计和制造的nanfluidic系统的一个关键因素，原子和分子建模nanofluidics是罕见的，大多数模拟在纳米级仅限于一维或二维的文献中，据我们所知。本工作介绍了原子尺度的设计和三维（3D）模拟的离子扩散纳米流体系统。我们提出了一个变分的多尺度框架来表示离散的原子和/或分子的细节，而描述的离子溶液的连续纳米通道。除了主要的静电和熵的影响，通道和溶液之间的非静电相互作用，溶剂分子之间的考虑在我们的建模。我们推导出纳米流体系统的广义Poisson-Nernst-Planck（PNP）方程。数学算法，如狄利克雷到诺依曼映射和匹配的接口和边界（MIB）的方法，严格解决上述方程的二阶精度在3D现实的设置。设计了三种离子扩散纳米流体系统，包括带负电荷的纳米通道、双极纳米通道和双阱纳米通道，研究了原子电荷对通道电流、密度分布和静电势的影响.数值计算的结果，如门控，离子耗尽和反转，与文献中的实验测量和数值模拟结果吻合良好。
英文摘要：
Recent advance in nanotechnology has led to rapid advances in nanofluidics, which has been established as a reliable means for a wide variety of applications, including molecular separation, detection, crystallization and biosynthesis. Although atomic and molecular level consideration is a key ingredient in experimental design and fabrication of nanfluidic systems, atomic and molecular modeling of nanofluidics is rare and most simulations at nanoscale are restricted to one- or two-dimensions in the literature, to our best knowledge. The present work introduces atomic scale design and three-dimensional (3D) simulation of ionic diffusive nanofluidic systems. We propose a variational multiscale framework to represent the nanochannel in discrete atomic and/or molecular detail while describe the ionic solution by continuum. Apart from the major electrostatic and entropic effects, the non-electrostatic interactions between the channel and solution, and among solvent molecules are accounted in our modeling. We derive generalized Poisson-Nernst-Planck (PNP) equations for nanofluidic systems. Mathematical algorithms, such as Dirichlet to Neumann mapping and the matched interface and boundary (MIB) methods are developed to rigorously solve the aforementioned equations to the second-order accuracy in 3D realistic settings. Three ionic diffusive nanofluidic systems, including a negatively charged nanochannel, a bipolar nanochannel and a double-well nanochannel are designed to investigate the impact of atomic charges to channel current, density distribution and electrostatic potential. Numerical findings, such as gating, ion depletion and inversion, are in good agreements with those from experimental measurements and numerical simulations in the literature.
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