Droplet plume emission during plasmonic bubble growth in ternary liquids

TL;DR

This study investigates droplet plume emission during plasmonic bubble growth in ternary liquids, revealing how ethanol concentration gradients and Marangoni effects lead to plume formation, with implications for enhanced mixing in various industries.

Contribution

It uncovers the mechanism of droplet plume emission in ternary liquids during plasmonic bubble growth, linking symmetry breaking to Marangoni number thresholds through experiments and simulations.

Findings

Droplet plumes are produced around growing plasmonic bubbles in ternary liquids.

The symmetry breaking of ethanol concentration causes plume emission.

Higher ethanol-water ratios increase plume emission, correlating with Marangoni number.

Abstract

Plasmonic bubbles are of great relevance in numerous applications, including catalytic reactions, micro/nanomanipulation of molecules or particles dispersed in liquids, and cancer therapeutics. So far, studies have been focused on bubble nucleation in pure liquids. Here we investigate plasmonic bubble nucleation in ternary liquids consisting of ethanol, water, and trans-anethole oil which can show the so-called ouzo-effect. We find that oil (trans-anethole) droplet plumes are produced around the growing plasmonic bubbles. The nucleation of the microdroplets and their organization in droplet plumes is due to the symmetry breaking of the ethanol concentration field during the selective evaporation of ethanol from the surrounding ternary liquids into the growing plasmonic bubbles. Numerical simulations show the existence of a critical Marangoni number Ma (the ratio between solutal advection rate and the diffusion rate), above which the symmetry breaking of the ethanol concentration field occurs, leading to the emission of the droplet plumes. The numerical results agree with the experimental observation that more plumes are emitted with increasing ethanol-water relative weight ratios and hence Ma. Our findings on the droplet plume formation reveal the rich phenomena of plasmonic bubble nucleation in multicomponent liquids and help to pave the way to achieve enhanced mixing in multicomponent liquids in chemical, pharmaceutical, and cosmetic industries.