Singular jets produced by oil-coated bubble bursting

Surface bubbles are ubiquitous in many natural and engineering processes, and bubble bursting aerosols are of particular interest because of their critical role in mass and momentum transfer across interfaces\ All prior studies claim that bursting of a millimeter-sized bare bubble at an aqueous surface produces jet drops with a typical size of O(100 μm), much larger than film drops of O(1 μm) from the disintegration of a bubble cap. Here, we document the hitherto unknown phenomenon that jet drops can be as small as a few microns when the bursting bubble is coated by a thin oil layer. We provide evidence that the faster and smaller jet drops result from the singular dynamics of the oil-coated cavity collapse. The unique 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 beyond that of a bare bubble. We further identify and rationalize the hydrodynamic conditions for the singular jet regime regarding the oil viscosity and coating fraction. As such contaminated bubbles are widely observed, the previously unrecognized fast and small jet drops may largely enhance bubble-driven flux across the interface, contributing to the aerosolization and long-range transport of any bulk substances.