Abstract.

Nonlinear effects on the electrophoresis of a soft particle, consisting of a rigid hydrophobic core coated with a diffuse polymer layer (PEL) suspended in an electrolyte medium, are studied. The impact of the ion partitioning effect arising due to the Born energy difference between the PEL and the electrolyte is approximated based on the equilibrium Boltzmann equation, with which the ion distribution and hence, the charge density is modified. The equations describing the electrokinetic transport comprising the Darcy-Brinkman extended Navier-Stokes equations which includes the ion partitioning effect coupled with the modified Nernst-Planck equations and Poisson equations for electric field are solved numerically. The present numerical model for the soft particle compares well with the existing theoretical solutions and experimental results in the limiting cases. A deviation from existing simplified models based on the Boltzmann distribution of ions occurs when the Debye layer polarization, relaxation and the electroosmosis induced by the PEL immobile charge become significant. The hydrophobicity of the inner core strongly influences the nonlinear electrokinetic effects by modifying the Debye layer, electroosmotic flow in the PEL and surface conduction. The results indicate that the ion partitioning can significantly increase the electrophoretic mobility of the soft particle by attenuating the shielding effect. When the Debye layer is in the order of the particle size the hydrophobicity of the core surface and the ion partitioning effect manifest the surface conduction, which implies that the Boltzmann distribution of ions is no longer valid. The core hydrophobicity and ion partitioning effect have influence on the condensation of the PEL immobile charge, which creates a significant impact on the mobility.

Graphical abstract

中文翻译：

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弥散性软颗粒核心的滑动速度和离子分配对迁移率的影响。

摘要。

研究了对软颗粒电泳的非线性影响，该软颗粒由刚性疏水核包裹，该疏水核包覆有悬浮在电解质介质中的扩散聚合物层（PEL）。基于平衡玻尔兹曼方程，可以估算由于PEL和电解质之间的Born能量差而引起的离子分配效应的影响，利用该方程可以修改离子分布并从而改变电荷密度。对包含达西-布林克曼扩展Navier-Stokes方程的电动迁移方程进行了数值求解，该方程包括离子分配效应，并结合了改进的Nernst-Planck方程和泊松方程。在有限的情况下，本发明的软颗粒数值模型与现有的理论解和实验结果很好地比较。当由PEL固定电荷引起的德拜层极化，弛豫和电渗变得明显时，就会发生与基于离子的玻尔兹曼分布的现有简化模型的偏离。内核的疏水性通过修饰Debye层，PEL中的电渗流和表面传导而强烈影响非线性电动效应。结果表明，离子分配可以通过减弱屏蔽作用来显着提高软颗粒的电泳迁移率。当德拜层的粒径在一定数量级时，核心表面的疏水性和离子分配作用表现出表面传导性，这意味着离子的玻耳兹曼分布不再有效。核心疏水性和离子分配作用对PEL固定电荷的缩合有影响，这对迁移率产生了重大影响。

图形概要