Modulating outcomes of oil drops bursting at a water-air interface

TL;DR

This paper explores methods to control oil drop bursting at water-air interfaces, demonstrating how adding particles or modifying interface properties can influence droplet formation and stability, with implications for oil-water separation processes.

Contribution

It introduces two novel approaches—particle addition and interface modification—to modulate bursting behavior, supported by theoretical criteria for outcome prediction.

Findings

Hydrophilic clay particles prevent daughter droplet formation.

Modified interfaces alter bursting regimes and outcomes.

Theoretical criteria predict droplet behavior based on drop constitution.

Abstract

Recent studies have shown that capillary waves generated by bursting of an oil drop at the water-air interface produces a daughter droplet inside the bath while part of it floats above it. Successive bursting events produce next generations of daughter droplets, gradually diminishing in size until the entire volume of oil rests atop the water-air interface. In this work, we demonstrate two different ways to modulate this process by modifying the constitution of the drop. Firstly, we introduce hydrophilic clay particles inside the parent oil drop and show that it arrests the cascade of daughter droplet generation preventing it from floating over the water-air interface. Secondly, we show that bursting behavior can be modified by a compound water-oil-air interface made of a film of oil with finite thickness and design a regime map which displays each of these outcomes. We underpin both of these demonstrations by theoretical arguments providing criteria to predict outcomes resulting therein. Lastly, all our scenarios have a direct relation to control of oil-water separation and stability of emulsified solutions in a wide variety of applications which include drug delivery, enhanced oil recovery, oil spills and food processing where a dispersed oil phase tries to separate from a continuous phase.