Chiu Ya C, Keh Huan J
Department of Chemical Engineering , National Taiwan University , Taipei 10617 , Taiwan , ROC.
J Phys Chem B. 2018 Oct 25;122(42):9803-9814. doi: 10.1021/acs.jpcb.8b06967. Epub 2018 Oct 16.
The quasi-steady diffusiophoresis of a charged porous sphere situated at the center of a charged spherical cavity filled with a liquid solution of a symmetric electrolyte is analyzed. The porous particle can represent a solvent-permeable and ion-penetrable polyelectrolyte molecule or floc of nanoparticles in which fixed charges and frictional segments are uniformly distributed, whereas the spherical cavity can denote a charged pore involved in microfluidic or drug-delivery systems. The linearized electrokinetic differential equations governing the ionic concentration, electric potential, and fluid velocity distributions in the system are solved by using a perturbation method with the fixed charge density of the particle and the ζ-potential of the cavity wall as the small perturbation parameters. An expression for the diffusiophoretic (electrophoretic and chemiphoretic) mobility of the confined particle with arbitrary values of a/ b, κ a, and λ a is obtained in closed form, where a and b are the radii of the particle and cavity, respectively; κ and λ are the reciprocals of the Debye screening length and the length characterizing the extent of flow penetration into the porous particle, respectively. The presence of the charged cavity wall significantly affects the diffusiophoretic motion of the particle in typical cases. The diffusio-osmotic (electro-osmotic and chemiosmotic) flow occurring at the cavity wall can substantially alter the particle velocity and even reverse the direction of diffusiophoresis. In general, the particle velocity decreases with an increase in a/ b, increases with an increase in κ a, and decreases with an increase in λ a, but exceptions exist.
分析了位于充满对称电解质液体溶液的带电球腔中心的带电多孔球体的准稳态扩散泳。多孔颗粒可以代表溶剂可渗透且离子可穿透的聚电解质分子或纳米颗粒絮凝物，其中固定电荷和摩擦段均匀分布，而球腔可以表示微流体或药物输送系统中涉及的带电孔。通过使用微扰方法，以颗粒的固定电荷密度和腔壁的ζ电位作为小扰动参数，求解了控制系统中离子浓度、电势和流体速度分布的线性化电动微分方程。得到了具有任意a/b、κa和λa值的受限颗粒的扩散泳（电泳和化学泳）迁移率的封闭形式表达式，其中a和b分别是颗粒和腔的半径；κ和λ分别是德拜屏蔽长度和表征流体渗透到多孔颗粒程度的长度的倒数。在典型情况下，带电腔壁的存在会显著影响颗粒的扩散泳运动。在腔壁处发生的扩散渗透（电渗透和化学渗透）流会极大地改变颗粒速度，甚至使扩散泳方向反转。一般来说，颗粒速度随a/b的增加而降低，随κa的增加而增加，随λa的增加而降低，但也存在例外情况。
