Electrophoresis of pH-regulated zwitterionic soft particle: a semi-analytical study

In this article, we made a parametric study on the electrophoresis of charge-regulated soft particle. We consider a typical situation where the outer polyelectrolyte layer (PEL) carries zwitterionic functional group (e.g., succinoglycan). In addition, the inner rigid core is considered to be made of either silicon dioxide (SiO2) or titanium dioxide (TiO2), which produces zwitterionic surface charge. The mathematical model adopted here is based on the Poisson-Boltzmann equation for electric potential and Darcy-Brinkman and Stokes equation for the fluid flow across the surface PEL and electrolyte medium, respectively. In our current study, we have restricted ourselves with the low charge and weak electric field assumption. Using semi-analytical method, we solve the governing equations and electrophoretic mobility of core-shell particle is obtained. We have studied extensively the effects of the pH and concentration of bulk electrolyte, charge properties of the inner core surface and outer PEL, radius of the inner core, and thickness of outer PEL, on the overall electrophoretic behavior of the undertaken particle. We have also highlighted the change in sign in electrophoretic mobility by regulating the pertinent parameters governing the problem.