Rheology of particulate rafts, films, and foams

Liquid foam exhibits remarkable rheological behavior although it is made with simple fluids: it behaves similar to a solid at low shear stress but flows similar to a liquid above a critical shear stress. Such properties, which have been proved to be useful for many applications, are even enhanced by adding solid particles. Depending on their hydrophobicity and size, the particles can have different geometrical configurations at the mesoscopic scale, that is, at the air-liquid interfaces, in the films, or in the interstices between the bubbles. In this review, we present rheological studies performed on granular rafts and films, on spherical armored interfaces, on gas marbles, and on aqueous foams laden with hydrophilic grains.