The effects of surfactant on the dynamics of bubble snap-off

The effects of an insoluble surfactant on the motion of a drop or bubble as it is driven by a pressure gradient through a capillary tube is investigated numerically. We find that a drop in a straight capillary tube can either approach a steady-state shape or develop a re-entrant cavity at its rear. For a gas bubble moving through a constricted capillary tube, we find that snap-off can occur and surfactants enhance the snap-off process. The effects of the parameters on the dynamics of bubble snap-off are illustrated and discussed.