Growth Rates of Hydrogen Microbubbles in Reacting Femtoliter Droplets

Abstract

Chemical reactions in small droplets are extensively explored to accelerate the discovery of new materials and increase the efficiency and specificity in catalytic biphasic conversion and high-throughput analytics. In this work, we investigate the local rate of the gas-evolution reaction within femtoliter droplets immobilized on a solid surface. The growth rate of hydrogen microbubbles (≥500 nm in radius) produced from the reaction was measured online with high-resolution confocal microscopic images. The growth rate of bubbles was faster in smaller droplets and near the droplet rim in the same droplet. The results were consistent for both pure and binary reacting droplets and on substrates of different wettability. Our theoretical analysis based on diffusion, chemical reaction, and bubble growth predicted that the concentration of the reactant depended on the droplet size and the bubble location inside the droplet, in good agreement with experimental results. Our results reveal that the reaction rate may be spatially nonuniform in the reacting microdroplets. The findings may have implications for formulating the chemical properties and uses of these droplets.

Review of Microscale Dynamics of Dilution-Induced Asphaltene Precipitation under Controlled Mixing Conditions

“…The effect of mixing dynamics on dilution-induced liquid–liquid phase separation has been extensively studied . Many hydrodynamic factors of the mixing process affect the morphology of the resulting droplet, including flow rate, diffusion coefficient, viscosity, and profile of the flow . The mixing dynamics also affect the asphaltene precipitation, considering the similarity of these two processes.…”

Review of microscale dynamics of dilution-induced asphaltene precipitation under controlled mixing conditions

“…The effect of mixing dynamics on dilution-induced liquid-liquid phase separation has been extensively studied [24]. Many hydrodynamic factors of the mixing process affect the morphology of the resulting droplet, including flow rate [5], diffusion coefficient [50], viscosity [51], and profile of the flow [52]. The mixing dynamics also affect the asphaltene precipitation, considering the similarity of these two processes.…”

Effects of Gas Type, Oil, Salts and Detergent on Formation and Stability of Air and Carbon Dioxide Bubbles Produced by Using a Nanobubble Generator

“…Moreover, microbubbles have been found to be effective in defouling contaminated surfaces [12,13]. Numerous methods have been developed for producing micro/nanobubbles on the surface of large substrates or particles in controlled systems, such as solvent exchange [14], (photo)catalytic reactions [15][16][17][18], electrolysis [19][20][21] and droplet reactions [22,23]. However, when generating micro/nanobubbles in large quantities, maintaining a large volume of water entirely free from impurities becomes an extremely challenging task with respect to studying bubble behavior in pure water.…”