Mechanics of bubble bursting in dilute oil-in-water emulsions

Abstract

Bubbles bursting at contaminated water surfaces aerosolize oil, microplastics, and pathogens, yet classical theory assumes a clean or surfactant-laden cap rupturing at a single hole. Using rupture-triggered high-speed shadowgraphy, digital in-line holography, and synchronized bubble-lifetime tracking on centimetric oil-in-water emulsion bubbles, we uncover multi-hole cap rupture with up to 47 holes opening in a single burst. Whereas size-matched solid spheres only thicken the film, oil droplets of positive spreading coefficient bridge the interfaces and excavate Marangoni thin spots. Conditioning on bubble lifetme shows that capillary-viscous drainage still sets film thickness while oil at the pinched foot drives upward Marangoni plumes that retard thinning. Consequently, increasing the oil fraction tenfold leaves film thickness at a given lifetime unchanged yet raises multi-hole probability from 2.3% to 40.1%, peaking within a 4 to 9 s lifetime window. Colliding Taylor-Culick rims form a ligament web that can amplify droplet yield by an order of magnitude, while scaling the classical law by the square root of the hole number collapses multi-hole yields onto one master curve.Finally, I discuss ongoing experiments on what triggers the sub-millisecond hole cascade and future directions across scales, including in-situ high-speed cap microscopy and PIV/PTV plume tracking of rise-height dependent oil enrichment, collective bursting in turbulent bubble rafts, and ocean spray measurements via UAV-borne anemometry and holography.

 About the Speaker

Dr. Cheng Li is an Associate Professor of Mechanical Engineering and Robotics at the Guangdong Technion-Israel Institute of Technology (GTIIT), which he joined in 2021. He received B.E. and B.S. degrees from Beihang University(2010) and a Ph.D. in Mechanical Engineering from Johns Hopkins University (2017), followed by postdoctoral research at the US DOE National Energy Technology Laboratory and the University of Minnesota. His research focuses on experimental multiphase physics, interfacial breakup, optical and holographic flow diagnostics, and UAV-based environmental sensing.