Qian Shizhi, Duval Jérôme F L
Department of Mechanical Engineering, University of Nevada-Las Vegas, 4505 Maryland Parkway, Las Vegas, NV 89154-4027, USA.
J Colloid Interface Sci. 2006 Aug 1;300(1):413-28. doi: 10.1016/j.jcis.2006.03.074. Epub 2006 May 24.
A theoretical model is proposed for the description of steady electroosmotic flows within a cylindrical electron-conducting microchannel that is depolarized by faradaic and adsorption-mediated processes. The bipolar electron-transfer (e.t.) reactions are examined in the general situation where the electrolyte contains a quasi-reversible redox couple. The rate of the e.t. reactions is governed by transversal convective diffusion of the electroactive species to/from the surface and a position-dependent degree of reversibility. The nonuniform distribution of the electric field in solution, that is intimately coupled to that of the local faradaic current density, alters the double layer composition along the conducting surface via the occurrence of simultaneous electronic and ionic double layer charging processes. This in turn generates a nonlinear distribution of the zeta potential, which affects the electroosmotic flow. The highly coupled spatial profiles for the concentrations of the electroactive species, the faradaic current density, the electrokinetic potential, the electric field and the electroosmotic velocity in/along the metallic channel are solved by consistent numerical analysis of (i) the convective-diffusion equation, (ii) the generalized Butler-Volmer expression that includes mass transport and electron-transfer kinetic contributions, (iii) the continuity and Navier-Stokes equations, and (iv) the Poisson equation for finite currents. The results reported as a function of the surface properties of the channel and the kinetic characteristics of the e.t. reaction illustrate the deviations of the electroosmotic flow profiles as compared to the typical pluglike distribution predicted by Smoluchowski's equation and encountered for homogeneous and dielectric channels. Manipulation of the flow patterns by bipolar electrochemical means is a promising way to control and optimize the local detection and separation of electroactive molecules or molecules dyed with electroactive elements.
提出了一个理论模型，用于描述圆柱状电子传导微通道内的稳态电渗流，该微通道通过法拉第过程和吸附介导过程去极化。在电解质包含准可逆氧化还原对的一般情况下，研究了双极电子转移（e.t.）反应。e.t.反应速率由电活性物质在表面的横向对流扩散以及位置相关的可逆程度决定。溶液中电场的非均匀分布与局部法拉第电流密度紧密相关，通过同时发生的电子和离子双层充电过程改变了导电表面的双层组成。这反过来又产生了zeta电位的非线性分布，从而影响电渗流。通过对以下方程进行一致的数值分析，求解了金属通道内/沿通道的电活性物质浓度、法拉第电流密度、动电电位、电场和电渗速度的高度耦合空间分布：（i）对流扩散方程；（ii）包含传质和电子转移动力学贡献的广义Butler-Volmer表达式；（iii）连续性方程和Navier-Stokes方程；（iv）有限电流的泊松方程。作为通道表面性质和e.t.反应动力学特征的函数报告的结果表明，与Smoluchowski方程预测的典型塞状分布相比，电渗流分布存在偏差，而这种典型分布在均匀和介电通道中会出现。通过双极电化学手段操纵流型是控制和优化电活性分子或用电活性元素染色的分子的局部检测和分离的一种有前途的方法。
