Enhanced singular jet formation in oil-coated bubble bursting

Bubble-bursting aerosols have a key role in mass and momentum transfer across interfaces. Previous studies report that the bursting of a millimetre-sized bare bubble at an aqueous surface produces jet drops with a typical size on the order of 100 μm. Here we show that jet drops can be as small as a few micrometres when the bursting bubble is coated by a thin oil layer. The faster and smaller jet drops result from the singular dynamics of the oil-coated cavity collapse. The air–oil–water compound interface offers a distinct damping mechanism to smooth out the precursor capillary waves during cavity collapse, leading to a more efficient focusing of the dominant wave and thus allowing singular jets over a much wider parameter space than that of a bare bubble. We develop a theoretical explanation for the parameter limits of the singular jet regime by considering the interplay between inertia, surface tension and viscous effects. Contaminated bubbles are widely observed, therefore previously unrecognized fast and small contaminant-laden jet drops may contribute to the aerosolization and airborne transmission of bulk substances.