Non-equilibrium electric double layers in narrow channels

基于泊松方程、能-普朗克方程、热输运方程和斯托克斯方程，从理论上研究了窄电解质填充通道内双电层（EDLs）的非平衡效应。首先，研究了轴向温度梯度对电解槽填充的影响。基于基础方程组的渐近展开，计算了EDL中由于热致力不平衡引起的流场。还将考虑与温度有关的壁ζ电位的影响。除了对方程进行解析处理外，还将采用数值解来检验解析模型的有效性范围，并探索超出该范围的参数空间。其次，探讨了通道壁上的化学反应对电渗透流动的影响。当新鲜的电解质通过平流进入通道时，壁上的化学平衡被扰乱，可能导致zeta电位的动态变化。这种效应及其对EOF的影响将基于对通道截面进行平均得到的降阶模型进行研究。该描述将包括一个简单的壁反应模型和离子扩散、平流和电迁移的面积平均输运项。该模型的参数研究将伴随着EOF速度随时间函数的测量实验。在申请人小组中进行的第一次实验已经表明，壁zeta电位可能是受通道内EOF影响的动态量。

Non-equilibrium effects in electric double layers (EDLs) inside narrow electrolyte-filled channels will be studied theoretically based on the combined Poisson, Nernst-Planck, heat transport and Stokes equations. Firstly, the effects of an axial temperature gradient on an electrolyte-filled slit-channel will be investigated. The flow field due to the thermally-induced force imbalance in the EDL will be computed based on asymptotic expansions of the underlying system of equations. The effect of a temperature dependent wall zeta potential will also be considered. Apart from the analytical treatment of the equations, numerical solutions will be employed to test the range of validity of the analytical model and to explore the parameter space beyond this regime. Secondly, the influence of chemical reactions at the channel walls on electroosmotic flow (EOF) will be explored. When fresh electrolyte is introduced into a channel via advection, the chemical equilibrium at the walls is disturbed, potentially resulting in dynamic changes of the zeta potential. This effect and its influence on EOF will be studied based on a reduced-order model obtained from averaging over the channel cross section. The description will incorporate a simple model for the wall reactions and area-averaged transport terms for the diffusion, advection and electromigration of ions. The parameter studies with this model will be accompanied by experiments in which the EOF velocity as a function of time is measured. First experiments conducted in the group of the applicant have already indicated that the wall zeta potential may be a dynamic quantity influenced by the EOF inside the channel.