Electroosmotic flow around a dielectric uncharged particle by considering the dielectric decrement effects
Electroosmotic flow around a dielectric uncharged particle by considering the dielectric decrement effects
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DOI：
10.1016/j.colsurfa.2018.03.037
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发表时间：
2018-06
期刊：
影响因子：
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通讯作者：
Partha Sarathi Majee;S. Bhattacharyya
中科院分区：
文献类型：
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作者：
Partha Sarathi Majee;S. Bhattacharyya
我们考虑了外加电场作用下化学惰性不带电介质粒子周围的电渗流。在外加电场存在的情况下，介电粒子可以被极化，从而产生不均匀的ζ势。认为电解液的介电常数随离子浓度的变化而变化。现有的研究要么在薄的德拜层假设下考虑理想导电粒子，要么考虑介电粒子。在这种情况下，感生EOF不仅受外加电场的影响，还受粒子的介电常数和德拜长度的影响。我们已经在没有引用薄层或弱外场假设的情况下分析了EOF。对控制的非线性电动力学方程进行数值求解。对于介质粒子和导电粒子的德拜薄层等极限情况，本文的计算解与已有的渐近分析非常接近，这是令人鼓舞的。通过Dukhin数测量的表面电导率，发现随着颗粒介电常数的增加而变大。Dukhin数与外加电场呈非线性关系。本文分析了介电损耗对EOF的影响。它会减少粒子周围的EOF。结果表明，当德拜长度与粒子大小成正比时，EOF对外加电场的依赖关系随粒子的介电常数而变化。然而，EOF与外加磁场强度的二次依赖关系发生在较薄的德拜层上。德拜长度的减少产生了增强的感应EOF。
We consider the electroosmotic flow (EOF) around a chemically inert uncharged dielectric particle under an applied electric field. In presence of an applied external electric field, a dielectric particle could be polarized to create an inhomogeneousζ-potential. The electrolyte permittivity is considered to vary with the ionic concentration. The existing studies consider either a perfectly conducting particle or dielectric particles under a thin Debye layer assumption. In the present case, the induced EOF is not only influenced by the applied electric field but also with the dielectric permittivity constant of the particle and Debye length. We have analyzed the EOF without invoking a thin layer or weak applied field assumptions. The governing nonlinear electrokinetic equations are solved numerically. The close agreement of the present computed solutions with the existing asymptotic analysis for limiting cases such as thin Debye layer for a dielectric particle and a conducting particle is encouraging. The surface conductivity, measured by the Dukhin number, found to become larger as the particle dielectric permittivity grows. The Dukhin number has a nonlinear dependence on the applied electric field. The dielectric decrement effects on the EOF have been addressed in the present analysis. It creates a reduction in the EOF around the particle. Our results show that when the Debye length is on the order of the particle size, the dependence of EOF on the applied electric field varies with the dielectric permittivity constant of the particle. However, a quadratic dependence of EOF on the applied field strength occurs at a thin Debye layer. Reduction in the Debye length creates an enhanced induced EOF.