Periodic bouncing of a plasmonic bubble in a binary liquid by competing solutal and thermal Marangoni forces

TL;DR

This study investigates the periodic bouncing of plasmonic bubbles in a binary water-ethanol liquid, revealing that competing solutal and thermal Marangoni forces cause the bubble's oscillatory motion, with implications for multicomponent liquid systems.

Contribution

It provides the first combined experimental and theoretical analysis of bubble bouncing driven by Marangoni forces in a binary liquid, highlighting the interplay of solutal and thermal effects.

Findings

Bubbles exhibit periodic attraction and repulsion at a few kHz.

The bouncing frequency depends on ethanol fraction and laser power.

Solutal and thermal Marangoni forces are identified as the driving mechanisms.

Abstract

The physicochemical hydrodynamics of bubbles and droplets out of equilibrium, in particular with phase transitions, displays surprisingly rich and often counterintuitive phenomena. Here we experimentally and theoretically study the nucleation and early evolution of plasmonic bubbles in a binary liquid consisting of water and ethanol. Remarkably, the submillimeter plasmonic bubble is found to be periodically attracted to and repelled from the nanoparticle-decorated substrate, with frequencies of around a few kHz. We identify the competition between solutal and thermal Marangoni forces as origin of the periodic bouncing. The former arises due to the selective vaporization of ethanol at the substrate's side of the bubble, leading to a solutal Marangoni flow towards the hot substrate, which pushes the bubble away. The latter arises due to the temperature gradient across the bubble, leading to a thermal Marangoni flow away from the substrate which sucks the bubble towards it. We study the dependence of the frequency of the bouncing phenomenon from the control parameters of the system, namely the ethanol fraction and the laser power for the plasmonic heating. Our findings can be generalized to boiling and electrolytically or catalytically generated bubbles in multicomponent liquids.