Bubble bursting at a viscoelastic surface: jet dynamics and bubble entrainment

Bubble bursting plays a key role in mediating the mass transport across the interface in nature and many industrial processes, such as sea spray aerosol generation and disease transmission from contaminant waters. A surface microlayer typically exists in natural bodies of water, which may contain proteins, bacteria, and viruses and behave as a viscoelastic surface. How the surface viscoelasticity affects the bubble bursting dynamics remains unclear. Here, we experimentally study the bursting of bubbles at the surface of bovine serum albumin (BSA) protein solutions. The increase in surface viscoelasticity decreases the jet velocity, jet height, and jet droplet number, and eventually kills the jet droplet ejection. In the regime of no jet droplet ejection, we observe the entrainment of a small gas bubble induced by the focusing of the capillary wave at the end of cavity collapse. The bubble entrainment is further discussed by investigating the effect of surface viscoelasticity on the capillary wave propagation during cavity collapse. These findings not only enrich the fundamental understanding of bubble bursting at a structurally complex surface, but also offer insights into the bubble-driven aerosolization of bulk substance such as pollutants.