Dissolution without disappearing: multicomponent gas exchange for CO sub(2) bubbles in a microfluidic channel

• Published in: Lab on a chip Vol. 14; no. 14; pp. 2428 - 2436
• Main Authors: Shim, Suin, Wan, Jiandi, Hilgenfeldt, Sascha, Panchal, Prathamesh D, Stone, Howard A
• Format: Journal Article
• Language: English
• Published: 01.06.2014
• Subjects: Bubbles; Carbon dioxide; Channels; Dissolution; Gas exchange; Mathematical models; Microfluidics; Sodium dodecyl sulfate
• ISSN: 1473-0197; 1473-0189
• DOI: 10.1039/c4lc00354c

We studied the dissolution dynamics of CO sub(2) gas bubbles in a microfluidic channel, both experimentally and theoretically. In the experiments, spherical CO sub(2) bubbles in a flow of a solution of sodium dodecyl sulfate (SDS) first shrink rapidly before attaining an equilibrium size. In the rapid dissolution regime, the time to obtain a new equilibrium is 30 ms regardless of SDS concentration, and the equilibrium radius achieved varies with the SDS concentration. To explain the lack of complete dissolution, we interpret the results by considering the effects of other gases (O sub(2), N sub(2)) that are already dissolved in the aqueous phase, and we develop a multicomponent dissolution model that includes the effect of surface tension and the liquid pressure drop along the channel. Solutions of the model for a stationary gas bubble show good agreement with the experimental results, which lead to our conclusion that the equilibrium regime is obtained by gas exchange between the bubbles and liquid phase. Also, our observations from experiments and model calculations suggest that SDS molecules on the gas-liquid interface form a diffusion barrier, which controls the dissolution behaviour and the eventual equilibrium radius of the bubble.