Distinct dynamics of jetting produced by bubble bursting at a structurally compound interface

Bursting of bubbles at a liquid surface is ubiquitous in a wide range of physical, biological, and geological phenomena, as a key source of aerosol droplets for mass transport across the interface. However, how a structurally compound interface, widely present in nature, mediates the bursting process remains largely unknown. Here, we present some of our recent studies considering the following configuration: 1) When a bare bubble bursting at an air-oil-water compound interface, we show that the coupling of oil spreading and cavity collapse dynamics results in a multi-phase jet and the follow-up jetted droplet size change (Nat. Commun. 2021). The jet radius and velocity are altered with even a thin oil layer, and oily aerosol droplets are produced. The coupling of oil spreading and cavity collapse dynamics results in a multi-phase jet and the follow-up droplet size change. Corresponding scaling laws are proposed to quantify the jetting dynamics; 2) When an oil-coated bubble bursting at an air-water interface, we show that jet drops can be a few microns, while prior studies report that the bursting of such a bare bubble produces jet drops with a size of the order of 100 µm (Nat. Phys. 2023). The faster and smaller jet drops result from the singular dynamics of the oil-coated cavity collapse, and the air-oil-water compound interface offers a distinct damping mechanism to smooth out the precursor capillary waves effectively; 3) when a protein-coated bubble bursts at a viscoelastic surface of a bovine serum albumin solution, we document an unexpected phenomenon that a daughter bubble is entrapped with no subsequent jet drop ejection, contrary to bare bubble bursting dynamics at a Newtonian surface (Phys. Rev. Lett. 2023). We show that the strong surface dilatational elastic stress from the viscoelastic surface retards the cavity collapse and effectively damps out the precursor waves. The onset of daughter bubble entrainment is well predicted by an interfacial elastocapillary number comparing the effects of surface dilatational elasticity and surface tension. Our work not only advances the fundamental understanding of bubble bursting dynamics, but also help reducing model uncertainty for bubble-mediated aerosol flux and airborne transmission of bulk substances.