ELECTROPHORESIS OF HIGHLY CHARGED HYDROPHOBIC MICRO- AND NANOPARTICLES
E. A. Frants1, E. N. Kalaidin1,2, A. A. Krylov2, E. A. Demekhin1,2,3
1Financial University under the Government of the Russian Federation, Moscow, Russia
2Kuban State University, Krasnodar, Russia
3Lomonosov Moscow State University, Institute of Mechanics, Moscow, Russia
Keywords: electrophoresis, hydrophobic surface, surface charge, nonlinear effect, electrolyte, slip velocity, surface conductivity, Dukhin number
Abstract
We investigate the electrophoresis of a dielectric particle possessing a hydrophobic surface and high surface conductivity through a combination of numerical simulations and analytical methods. Our results show that, under a moderate electric field and high surface charge density, the particle velocity increases, with the contribution from surface conductivity significantly exceeding that of the slip length. An analytical expression for the electrophoretic mobility of a hydrophobic particle is derived. This formula consists of three terms: (1) the linear term from the classical Helmholtz-Smoluchowski relation; (2) a term accounting for the hydrophobic surface effect; (3) a term representing the contribution of surface conductivity induced by the high surface charge density. Results are presented for both small and large slip lengths, corresponding to micro- and nanoparticles, respectively. A comparison between the numerical and analytical solutions demonstrates excellent agreement between the two approaches.
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