Bubble pinch-off with and without surfactants

Bubble formation and bursting are ubiquitous in our daily lives. Well known examples include bubbles in carbonated beverages and blowing soap bubbles. More importantly, bubble formation has applications in industrial processes involving gas-liquid contacting, e.g. distillation, gas-liquid absorption, multiphase gas-liquid reactions, and bio-chemical reactions. In a pioneering study, Burton et al. (Phys. Rev. Lett., 2005) experimentally investigated the pinch-off dynamics of bubbles immersed in a pool of high viscosity liquid and demonstrated that the minimum neck radius of bubbles scales linearly with time remaining to pinch-off. However, in many applications, surfactants are often present on the gas-liquid interface either by design or as contaminants. Presence of surfactants reduces the surface tension of the interface. Moreover, non-uniform distribution of surfactants along the interface causes surface tension gradients which give rise to Marangoni stresses. In this talk, we will present results on the pinch-off dynamics of bubbles in a pool of high viscosity liquid when the interface is clean as well as when it is covered with a monolayer of an insoluble surfactant. A salient feature of the work is to identify scaling regimes that arise as the bubble approaches pinch-off.