Surfactant-driven dynamics of liquid lenses

Abstract

Sessile liquid lenses spreading over a fluid layer, in the presence of Marangoni stresses due to surfactants, show a surprisingly wide range of interesting behaviour ranging from complete spreading of the lens, to spreading followed by retraction, to sustained pulsating oscillations. Models for the spreading process, the effects of surfactant at the moving contact line, sorption kinetics above and below the critical micelle concentration, are all incorporated into the modelling. Numerical results cast light upon the physical processes that drive these phenomena, and the regular oscillatory beating of lenses is shown to occur in specific limits.