MechSE Assistant Professor Jie Feng, Alexander Rankin Professor Randy Ewoldt, postdoctoral researcher Bingqiang Ji, graduate students Zhengyu Yang, and undergraduate student Zirui Wang recently published in Physical Review Letters. Their article, “Secondary Bubble Entrainment via Primary Bubble Bursting at a Viscoelastic Surface,” builds on ongoing work that investigates the impact of bubble bursting on aerosolization of contaminants.
When a bubble rises through a liquid and bursts at the surface, it can produce ejected droplets that play a key role for mass transfer in both natural and industrial processes. For instance, because these droplets are important sources for sea spray, their evaporation affects the atmosphere’s radiative balance and serves as cloud condensation nuclei. Furthermore, ocean surfaces are often contaminated by complex organic matters such as proteins and lipids that form a “viscoelastic” surface layer. The team’s most recent work documents a new bubble bursting regime in which a daughter bubble is entrapped by the collapsing bubble cavity at such a surface—unlike for Newtonian fluids, which have a drop ejection regime, the team found that drop ejection was suppressed for a protein-adsorbed viscoelastic surface layer.
“Our work highlights that the surface viscoelasticity can dramatically change bubble bursting dynamics as well as the resulting droplet ejection and aerosol production,” said Feng, noting that entrapping small, protein-enriched bubbles may enhance gas adsorption and protein transport in liquids while also inhibiting the aerosolization process associated with bubble bursting. “Our findings may advance the understanding of mass transfer related to bubble bursting in natural and engineered water bodies, where organic macromolecules are widely present to form such viscoelastic surfaces.”
The researchers look forward to further exploring the implications of their findings, such as investigating the composition of ejected droplets to understand how organic contaminants in the bulk water are transported to the atmosphere.
“It’s a joy to work with such outstanding trainees and colleagues,” Ewoldt said. “Moreso because this study is deeply interesting scientifically and with important implications for bubble bursting dynamics that occur in both engineered systems and natural environments.”
The team acknowledged the support given by the Department of Mechanical Science and Engineering at UIUC to enable this work.