Chiara Neto, School of Chemistry and University of Sydney Nano Institute, The University of Sydney, NSW 2006 Australia
Dissolved atmospheric gases are typically assumed to have negligible influence on liquid behaviour because their solubility is too low to affect macroscopic properties. However, long‐standing observations contradict this view: for example, it is well known that dissolved gases can accumulate at solid hydrophobic surfaces immersed in water;1 the emergence of long-range hydrophobic interactions has been ascribed to nanobubble cavitation between two hydrophobic surfaces;2 as the concentration of dissolved gases in an oil-in-water emulsion decreases, the average time of droplet coalescence significantly increases.3,4 In this work, we developed a precise droplet rise experiment that explores the boundary conditions for flow at oil microdroplets as a function of the gas content.5 By using high speed shadowgraphy, we measure a faster rise velocity for microdroplets of oil (silicone oil and hexadecane) released in quiescent gassed water, than expected based on a no-slip boundary condition. We fit the rise velocity with a slip length that increases from a few μm for partially gassed liquids, to tens of μm for fully gassed water. Interfacial gas enrichment governs these effects, in the form of gas
layers forming at the liquid-liquid interface, of thickness up to several hundred nanometers. Negligible or negative slip was measured for contaminated systems, confirming that the liquid-liquid interface becomes immobilised when impurities are present.
1. Lohse, D. et al., Rev. Mod. Phys. 87, 981-1035, (2015).
doi.org/10.1103/RevModPhys.87.981
2. Christenson, H. K. et al., Adv. Colloid Interface Sci. 91, 391-436 (2001).
3. Eastoe, J. et al., Adv. Colloid Interface Sci. 134-135, 89-95 (2007).
doi.org/10.1016/j.cis.2007.04.017
4. Wang, J. et al., Langmuir 35, 3615-3623 (2019). doi.org/10.1021/acs.langmuir.8b03486
5. Azadi, R., Giacomello, A. & Neto, C. Interfacial gas enrichment at rising oil droplets.
(in preparation (2026)
Data: Giovedì 11 giugno - ore 11:00
Luogo: Aula videoconferenze, DIMA, Via Eudossiana 18, Roma
ScadenzaNotizia 11/06/2026