Entropic wetting of a colloidal rod-sphere mixture

We investigate the behavior of a model colloidal mixture of hard spheres and rod-like particles near a planar hard wall using density functional theory. For small size ratios of rod length and sphere diameter we find that the colloidal liquid phase wets the wall completely upon approaching the fluid demixing binodal from the colloidal gas side, provided the density of the rods lies below the wetting point. Using an effective one-component description based on the pairwise depletion potential for higher density of rods, a finite sequence of layering phase transitions is found. For large rod-to-sphere size ratios, using a binary treatment, thick films are obtained even close to the triple point.