Rheology of foams and highly concentrated emulsions

We review the state of the art in foam and highly concentrated emulsion rheology, with an emphasis on progress made over the last five years. Since the structures and physico-chemical processes relevant for foams and emulsions are closely analogous, comparing the knowledge recently gained in these two neighboring fields brings fresh insight. In this spirit, we review how the macroscopic mechanical response arises from a coupling between interfacial energy and long range molecular interactions, entropic effects, interfacial rheology, and dynamics at the droplet or bubble scale. We present experiments and models concerning elasticity, osmotic pressure, yielding and flow behavior. [Display omitted] •Osmotic pressure and shear modulus are due to capillary and entropic forces.•Yielding in 3D follows the von Mises criterion.•Linear and non-linear wall friction depends on bubble confinement and velocity.