Depletion forces in colloidal mixtures

Depletion forces are accounted for by a contraction of the description of colloidal mixtures based on the integral equations theory of simple liquids. The applicability of this treatment is illustrated for binary mixtures of hard spheres, in the bulk and near a hard wall. The Asakura and Oosawa potential is obtained as the dilute limit of our equations. At higher concentrations the depletion potential has an oscillatory behavior and becomes more long ranged. If charge is put on the small particles there are energy-driven depletion forces in addition to those of entropic origin, which result in repulsive interaction at contact.