A brief history of the physics of foams

A liquid foam is a dense packing of gas bubbles in a relatively small amount of surfactant solution, and is common in daily life. However, the physics underlying foams is poorly understood. For example, sudsy foam somehow behaves like a springy solid or flows like a fluid, despite being made almost completely of air. The statics of dry foams was established around the late 19th century through, for instance, the laws of equilibrium of foam structure proposed by J. A. Plateau in 1873, and the optimal division of space with a tetrakaidecahedra (i.e. Kelvin’s partition) by W. Thomson (Lord Kelvin) in 1887. After nearly a century’s silence, research on the statics of dry foams was rekindled in 1992 by K. Brakke’s development of software for modeling liquid surfaces shaped by various forces and constraints, and the consequent finding of the Weaire-Phelan partition in 1993. Since the 1980s the dynamics of both dry and wet foams became the focus of foam physics, but many challenges such as the rheological properties, instabilities and so on still remain.