Influence of fluid flows on electric double layers in evaporating colloidal sessile droplets

Abstract

A model is developed for describing transport of colloidal silica particles in an evaporating aqueous sessile droplet on the electrified metal substrate in the presence of a solvent flow. The model takes into account the electric charge of colloidal particles and small ions produced by electrolytic dissociation of the active groups on the colloidal particles and water molecules. We employ a system of self-consistent Poisson and Nernst-Planck equations for electric potential and average concentrations of colloidal particles and ions with the respective boundary conditions. The developed model is used to make a first-principles numerical simulation of charged colloidal particle transport. We find that electric double layers can be destroyed by a sufficiently strong fluid flow such as Marangoni flow. Capillary fluid flows cannot destroy the electric double layer because they are much weaker than Marangoni flows.