Electrophoresis of a Concentrated Dispersion of Nonrigid Particles

Abstract

Electrophoresis is one of the most important analytical tools for the quantification of charged entities in a dispersing medium. Although the electrophoresis of rigid entities has been studied extensively in the literature, corresponding analysis on nonrigid entities is relatively limited. The present study focuses on the electrophoresis of a concentrated dispersion of nonrigid particles for the case when the effect of double layer polarization may be significant. In particular, the effects of the surface potential of the particle, the volume fraction of the particles, the ratio (viscosity of the medium inside the particle/viscosity of the medium outside the particle), and the double layer thickness are discussed. Various phenomena specific to nonrigid entities that are not observed for the case of rigid entities are observed in this study, which include, for example, the fact that the variation of electrophoretic mobility as a function of double layer thickness exhibits an inflection point. We show that, under the same conditions, the electrophoretic mobility of a nonrigid particle is larger than that of a rigid particle, and this is pronounced if the double layer is thin.

Mechanistic studies of droplet electrophoresis: A review

“…Additionally, at the droplet surface, a tangential component of the velocity field exists, while at particle surfaces, the no‐slip boundary condition holds [35, 40, 59, 64]. The slip velocity boundary condition leads to the formation of a velocity field inside the droplet affecting the EP mobility [41, 44]. These differences have to be taken into account to accurately describe droplet EP, and will be further elaborated upon next.…”

“…These differences have to be taken into account to accurately describe droplet EP, and will be further elaborated upon next. Generally speaking, droplets move faster, compared to rigid particles with similar ‐potential, because of a smaller effective hydrodynamic drag force exerted on them [41, 44, 65, 66].…”

“…With increasing ‐potential, more surface charges will be redistributed and therefore, the surface potential gradient on the droplet will increase. As a result, a stronger retarding force will be exerted on the droplet leading to a reduction of its mobility [41, 78]. It has been shown that EDL polarization is significant for and the influence will be reduced for lower or higher values of [44, 49, 79].…”

“…EP of droplets is more complicated than particle EP because of specific characteristics of droplets such as mobile surface charges [39], a flexible interface, and slip velocities on their surface [40]. The possibility of internal flows inside droplets adds further complexity to the description of droplet EP mobility [41]. Several researchers have investigated the influence of these parameters on droplet mobility [40, 42–44].…”

Electrophoresis of a non-conducting Newtonian drop of low electrical potential normal to a plane

“…Solving the electrokinetic equations for a non-rigid dispersion is usually more complicated than solving those for a rigid dispersion since both the flow and the electric fields inside a non-rigid entity need be considered. The electrophoretic behaviors of non-rigid particles was investigated for an isolated mercury drop (Craxford et al, 1937;Booth, 1951;Levich, 1962;Levine and O'Brien, 1973), an isolated drop or gas bubble (Baygents and Saville, 1991a,b;Ohshima, 2003), a dispersion of mercury drops (Ohshima et al, 1984;Ohshima, 1997Ohshima, , 1999Lee et al, 2003a), a dispersion of general non-rigid particles (Kelsall et al, 1996;Lee et al, 2003b), and a dispersion of non-Newtonian drops (Lee et al, 2005a).…”