Measurements of Static and Dynamic Bubble Surface Tension Using a Deformation-Based Microfluidic Tensiometer

Area of Science:

• Multiphase flow dynamics
• Interfacial phenomena
• Surface chemistry

Background:

• Surface tension is crucial for liquid-gas systems like aerosols and foams.
• Dynamic surface tension decay, influenced by bubble size and surfactants, impacts multiphase system behavior.
• Microfluidic techniques, well-established for liquid-liquid systems, are less explored for liquid-gas interfaces.

Purpose of the Study:

• To employ microfluidics for measuring static and dynamic surface tension of microscale bubbles.
• To compare microfluidic measurements with traditional pendant drop methods for millimeter bubbles.
• To investigate the influence of bubble size and surfactant concentration on surface tension dynamics.

Main Methods:

• Utilized a high-throughput microfluidic tensiometer for microscale bubble analysis.
• Employed pendant drop tensiometry for characterizing millimeter bubbles.
• Investigated surfactant-free and surfactant-laden interfaces under varying conditions.

Main Results:

• Microfluidic static surface tension measurements agreed well with pendant drop for surfactant-free systems.
• Factors like bubble pressure and inertia can affect microfluidic static measurements.
• Smaller bubbles and higher surfactant concentrations significantly reduced the time to reach equilibrium dynamic surface tension.

Conclusions:

• Microfluidic tensiometry offers a viable method for studying dynamic surface tension decay in microscale bubbles.
• The technique captures early-time surface tension changes and is robust against Marangoni stress.
• This approach enhances the study of interfacial dynamics in complex liquid-gas systems.