Dissolution without disappearing: multicomponent gas exchange for CO2 bubbles in a microfluidic channel.

Area of Science:

• Fluid dynamics
• Physical chemistry
• Materials science

Background:

• Understanding gas bubble dissolution is crucial in various industrial and biological processes.
• Microfluidic systems offer controlled environments for studying dynamic phenomena like bubble dissolution.
• Previous studies often simplified bubble behavior, neglecting multicomponent gas effects and surfactant influences.

Purpose of the Study:

• To investigate the dissolution dynamics of carbon dioxide (CO2) bubbles in a microfluidic channel.
• To elucidate the factors controlling the equilibrium size of CO2 bubbles.
• To develop and validate a theoretical model for CO2 bubble dissolution in surfactant solutions.

Main Methods:

• Experimental observation of CO2 bubble dissolution in sodium dodecyl sulfate (SDS) solutions using microfluidics.
• Development of a multicomponent dissolution model incorporating surface tension and pressure drop.
• Theoretical analysis of gas exchange between bubbles and the aqueous phase.

Main Results:

• CO2 bubbles exhibited rapid shrinkage followed by attainment of an equilibrium size.
• The time to reach equilibrium was independent of SDS concentration (approx. 30 ms).
• The equilibrium bubble radius was dependent on SDS concentration, suggesting a diffusion barrier.

Conclusions:

• Equilibrium in CO2 bubble dissolution is achieved through gas exchange between the bubble and the surrounding liquid.
• Sodium dodecyl sulfate (SDS) molecules at the gas-liquid interface create a diffusion barrier, controlling dissolution rate and final bubble size.
• The developed multicomponent model accurately predicts experimental observations of CO2 bubble dissolution dynamics.