Bubble nucleation and dynamics: surface micro/nanobubbles and plasmonic microbubbles

Bubbles are widely present in numerous natural and industrial processes. Understanding the nucleation mechanism and dynamics of the bubbles is essential for exploiting relevant applications in material engineering, microfluidics, catalysis and electrolysis and many others. In this thesis, we have focused on two categories of bubbles:
(i) Surface micro/nanobubbles on structured surfaces. We studied the entrapment of nanobubbles at the solid-liquid interface on nanostructured hydrophobic surfaces. Results show that the morphology and density of the trapped surface nanobubbles depends on the type of nanostructures. This verifies that the pinning effect of surface structures contributes to surface nanobubble nucleation and stability. Furthermore, the entrapment and evolution of microbubbles on a hydrophobic structured surface with microwells are investigated. We find that after nucleation, the microbubbles formed on the microwells dissolve in a constant contact angle mode. We also quantify how a high gas undersaturation enhances the dissolution process by varying the gas undersaturation level.
(ii) Plasmonic microbubbles. We studied the gas effect on plasmonic bubble dynamics in water and bubble formation in binary and ternary liquid system. It is found that in pure water, the bubble nucleation temperature depends on the gas concentration and the long-term bubble growth is governed by gas diffusion. In binary liquids of water-ethanol mixtures, we find that plasmonic bubbles exhibit ethanol concentration-dependent behavior. We reveal the mechanism of the formation of the unstable bubbles in binary liquids at low ethanol concentration, and the sudden bubble shrinkage during stable bubble growth in liquids with high ethanol ratios. Finally, plasmonic bubble nucleation in ternary liquids consisting of ethanol, water, and trans-anethole oil is investigated. It is observed that oil (trans-anethole) droplet plumes are produced around the growing plasmonic bubbles. The nucleation and self-organization of droplet plumes depends on the ethanol-water relative weight ratio and hence Marangoni number.