Particle-Assisted Wetting

The wetting of a solid surface by a liquid is dramatically impeded if either the solid or liquid is decorated by particles. Here, we show that in the case of contact between two liquids the opposite effect can occur; mixtures of a hydrophobic liquid and suitable particles form wetting layers on a water surface, though the liquid alone is nonwetting. In these wetting layers, the particles adsorb to and partially penetrate through the liquid/air and/or liquid/water interface. This formation of wetting layers can be explained by the reduction in the total interfacial energy due to the replacement of part of the fluid/fluid interfaces by the particles. Furthermore, one can observe wetting layers of a thickness considerably larger than the particle diameter. This indicates that, in addition to their surfactant-like properties, particles adsorbed to an interface can compensate unfavorable long-range interactions.