Wetting-induced aggregation of colloids

More than two decades ago, in a seminal paper John Cahn proposed scaling ar guments for the possibility of a wetting transition in two coexisting fluid phases near the critical point. Since then, Cahn's model has been tested i n many fluid systems and further refined by including the real interactions between the fluid and the solid wall. A fascinating consequence of the exi stence of a wetting transition is the possibility for a transition from wea k to strong adsorption in the homogeneous phase. The situation is further e nriched in nonstandard geometries having special geometrical constraints. T he subject of this review concerns one such situation, where charge-stabili zed colloidal particles are suspended in the homogeneous region of a binary liquid mixture. In this case, the preferential adsorption of one of the li quid components on to the colloid surface completely modifies the stability of the particles leading to an aggregation process. Although the exact mec hanism underlying the adsorption phenomenon is still debated, it is closely related to the wetting transition. Recent experimental developments concer ning the static and dynamic aspects of this phenomenon are reviewed. In add ition, the main findings of a theoretical model based on the adsorption-mod ified electrostatic interactions between the colloidal particles are discus sed.