The physicochemical hydrodynamics of bubbles and droplets out of equilibrium, in particular with phase transitions, display 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 kilohertz. We identify the competition between solutal and thermal Marangoni forces as the 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 toward 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 toward 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.
Metal
nanoparticles under laser irradiation can produce enormous heat due
to surface plasmon resonance. When submerged in a liquid, this can
lead to the nucleation of plasmonic bubbles. In the very early stage,
the nucleation of a giant vapor bubble was observed with an ultrahigh-speed
camera. In this study, the formation of this giant bubble on gold
nanoparticles in six binary liquid combinations has been investigated.
We find that the time delay between the beginning of the laser heating
and the bubble nucleation is determined by the absolute amount of
dissolved gas in the liquid. Moreover, the bubble volume mainly depends
on the vaporization energy of the liquid, consisting of the latent
heat of vaporization and the energy needed to reach the boiling temperature.
Our results contribute to controlling the initial giant bubble nucleation
and have strong bearings on applications of such bubbles.
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