Binary colloidal mixtures in a potential barrier: Demixing due to depletion

Abstract

Depletion interaction between an infinite repulsive potential and larger species in a binary mixture is known to arise when the binary mixture is confined by hard or soft repulsive balls. We report that such depletion interactions can arise even if the binary mixture is subjected to a finite potential barrier. This leads to an increased number density of large particles in the region of potential barrier and subsequently to a microstructural domain formation. We investigate the effect of relative volume fraction of the components, height and width of the potential barrier, total volume fraction of the particles, and the size ratio of the particles on this microstructural transition.