包覆纳米胶囊中电渗流的理论研究
Electro-osmotic flow in coated nanocapillaries: a theoretical investigation
摘要：
最近的实验的动机，我们提出了一个理论研究如何在毛细管中发生的电渗流被修改时，其带电的表面被带电的聚合物涂层。理论处理是基于一个三维模型，由一个三元流体混合物，代表溶剂和两个物种的离子，限制在两个平行的带电板之间的装饰由一个固定的阵列的散射体代表的聚合物涂层。电渗流，由一个恒定的电场施加在平行于板的方向上产生的，通过格子Boltzmann模拟数值研究。为了获得进一步的理解，我们进行了一个简单的理论分析，通过扩展的斯托克斯-Smoluchowski方程，考虑到孔隙率引起的聚合物在邻近的区域的墙壁。我们讨论的速度分布的性质，通过专注于竞争的聚合物电荷和它们施加的摩擦力的影响。我们显示的流动减少和流动反转现象时，聚合物的电荷是相反的表面电荷的证据。通过使用聚合物的密度和表面电荷作为控制变量，我们提出了一个相图，区分的直接和反向流制度，并确定其依赖于离子浓度。
英文摘要：
Motivated by recent experiments, we present a theoretical investigation of how the electro-osmotic flow occurring in a capillary is modified when its charged surfaces are coated by charged polymers. The theoretical treatment is based on a three dimensional model consisting of a ternary fluid-mixture, representing the solvent and two species for the ions, confined between two parallel charged plates decorated by a fixed array of scatterers representing the polymer coating. The electro-osmotic flow, generated by a constant electric field applied in a direction parallel to the plates, is studied numerically by means of Lattice Boltzmann simulations. In order to gain further understanding we performed a simple theoretical analysis by extending the Stokes-Smoluchowski equation to take into account the porosity induced by the polymers in the region adjacent the walls. We discuss the nature of the velocity profiles by focusing on the competing effects of the polymer charges and the frictional forces they exert. We show evidence of the flow reduction and of the flow inversion phenomenon when the polymer charge is opposite to the surface charge. By using the density of polymers and the surface charge as control variables, we propose a phase diagram that discriminates the direct and the reversed flow regimes and determine its dependence on the ionic concentration.
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