Comparative Study on the Electrophoresis of Soft and Semisoft Nanoparticles

There is abundant literature that deals with the electrophoresis of biocolloids and environmental entities. Most of these nanoparticles can be classified as soft particles, which are core-shell structured in nature. Most existing studies assume the inner core of the soft particles to be rigid in nature. However, there are various core-shell structured nanoparticles for which the inner core is semisoft in nature, which allows ion penetration but restricts fluid flow. In addition, the distribution of the peripheral layer of the soft (soft particle with rigid inner core) or semisoft (soft particle with semisoft inner core) particle is not necessarily uniform. In the present article, we consider the electrophoresis of soft and semisoft particles with the diffuse distribution of monomers across the peripheral shell layer. The mathematical model adopted here is based on the Poisson-Boltzmann equation for the electric double-layer potential and Darcy-Brinkman extended Stokes equation for fluid flow. The study is carried out considering a weak electric field assumption, which allows us to linearize the set of equations using perturbation analysis. A finite difference-based method is adopted to solve the perturbed set of equations and thus to calculate the electrophoretic mobility. The results are presented to indicate the difference in electrophoretic mobility of soft and semisoft particles under similar electrostatic conditions. We have further indicated the dependence of pertinent parameters on the electrophoretic mobility of soft or semisoft nanoparticles.