Dynamic electrophoresis of concentrated droplet dispersions at arbitrary surface potentials

Lou, James; Lee, Eric

doi:10.1016/j.ces.2007.07.032

Cited by 7 publications

(1 citation statement)

References 32 publications

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“…For fluid droplets, the flow field inside and outside the droplet needs to be considered along with appropriate interfacial conditions. Note that the controlled electrokinetic transport of tiny droplets finds their potential applications in several fields, namely, in microfluidic and nanofluidic operations, to separate water-in-oil emulsions, in biomedical and biochemical applications, and in food and cosmetic industries. , Lee and co-researchers extensively studied the electrophoresis of liquid droplets under an alternating electric field, considering droplets in a spherical cavity, and a concentrated suspension of droplets with a low or arbitrary surface potential . In all of these studies, the undertaken droplet bears a uniform surface potential and is certainly possible when the droplet behaves like a perfect conductor and the flow field outside the droplet is not influenced by the inner fluid.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Electrophoresis of a Hydrophobic and Dielectric Fluid Droplet

Chowdhury,

Mahapatra,

Ohshima

et al. 2023

Langmuir

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Dynamic electrophoresis is the foundation for electroacoustical measurements, in which the electroacoustical signals may be used to analyze the size and electrostatic charge of colloidal entities by means of the results for dynamic electrophoretic mobility. Thus, the electrophoresis under an alternating electric field is the key foundation for electroacoustic theory. In this article, we develop a tractable analytical theory for the dynamic electrophoresis of hydrophobic and dielectric fluid droplets possessing uniform surface charge density. The tiny fluid droplets possess charged mobile surfaces and have found widespread applications in our day-to-day life. For dielectric fluid droplets (e.g., oil–water emulsions), the tangential electric stress at the interface is nonzero, which significantly affects its electrohydrodynamics under an oscillatory electric field, which has, however, a negligible impact on the electrophoretic motion of conducting droplets (e.g., mercury droplets). Besides, the micro/nanoscale fluid droplets often show hydrophobicity when they are immersed in an aqueous medium, and the impact of the electric field on hydrophobic surfaces remains a research frontier in the chemical discipline. Whereas a number of approximate expressions for electrophoretic mobility have been derived for the conducting droplet, none of them are applicable to such generic hydrophobic fluid droplets with dielectric permittivity that is significantly lower than or comparable to that of an aqueous medium. In this work, within the Debye–Hückel electrostatic framework, we elaborate an original analytical expression of dynamic electrophoretic mobility for this generic dielectric fluid droplet with a hydrophobic surface considering that the droplet retains its spherical shape during its oscillatory motion. We further derived a set of simplified expressions for dynamic electrophoretic mobility deduced under several limiting cases. The results are further illustrated, indicating the impact of pertinent parameters.

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