Plasmonic Microbubble Dynamics in Binary Liquids

Abstract

The growth of surface plasmonic microbubbles in binary water/ethanol solutions is experimentally studied. The microbubbles are generated by illuminating a gold nanoparticle array with a continuous wave laser. Plasmonic bubbles exhibit ethanol concentration-dependent behaviors. For low ethanol concentrations ( f e ) of ≲67.5%, bubbles do not exist at the solid–liquid interface. For high f e values of ≳80%, the bubbles behave as in pure ethanol. Only in an intermediate window of 67.5% ≲ f e ≲ 80% do we find sessile plasmonic bubbles with a highly nontrivial temporal evolution, in which as a function of time three phases can be discerned. (1) In the first phase, the microbubbles grow, while wiggling. (2) As soon as the wiggling stops, the microbubbles enter the second phase in which they suddenly shrink, followed by (3) a steady reentrant growth phase. Our experiments reveal that the sudden shrinkage of the microbubbles in the second regime is caused by a depinning event of the three-phase contact line. We systematically vary the ethanol concentration, laser power, and laser spot size to unravel water recondensation as the underlying mechanism of the sudden bubble shrinkage in phase 2.

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

“…6.3a and b we plotted the volume of the plasmonic bubble versus time and the maximum number of droplet plumes versus the ethanol ratio r e/(e+w) . Not surprisingly, the bubble growth in the ternary liquids here is very comparable to the bubble growth in ethanol-water binary liquids [167]. As shown in Fig.…”

“…As a result, anethole oil has limited influence on the vaporization process and the bubble growth in the ternary liquids. A larger relative ethanol fraction in ethanol-water binary liquids results in a large bubble growth rate [167]. The maximum plume number, N max , was found to increase with increasing r e/(e+w) , see Fig.…”

“…The seven ternary liquids were actually labelled with increasing ethanol-water relative weight ratio of r e/(e+w) = y e /(y e + y w ), which hereafter is used for analysis. At low ethanol concentrations, the plasmonic bubbles depin and detach due to the strong upward Marangoni force, which has been systematically investigated in our previous study [167]. In contrast, bubbles can steadily attach to the substrate at high ethanol fractions.…”

“…We have recently started this line of research and investigated plasmonic bubble nucleation in binary liquids of ethanol and water, and found that the solutal Marangoni flow, caused by the preferential vaporization of ethanol, results in the detachment of the bubbles from the substrate at low ethanol ratios (< 67.5%) [167]. In binary liquids with ethanol ratios exceeding 67.5%, on the contrary, bubbles remain attached to the substrate and first steadily grow until they suddenly shrink.…”

Nucleation and dynamics of bubbles/droplets in multicomponent liquids

“…In contrast, later the ordinary plasmonic bubbles contain both vapor and gas and are substantially larger. Therefore, the laser spots are then completely isolated from the water by the growing plasmonic bubbles [63]. Consequently, the heat at the laser spots cannot be directly transferred into the surrounding liquid.…”