The dynamic adsorption of different surfactants on droplet formation in coaxial microfluidic devices

• The dynamic adsorption of different surfactants were systematically studied during droplet formation in microfluidic devices.
• The different dynamic interfacial tension tendency for micromolecule and macromolecule surfactant was studied.
• The transition of the kinetic of surfactant absorption, from mass transfer limited model to mixed kinetic model, was discussed.
• The turning concentration points of tendency may give a new approach to determinate the CMC of surfactants in microfluidic devices.

In this work, the dynamic adsorption of different surfactants is studied during droplet formation in microfluidic devices. For a macromolecule surfactant (Tween 20 and TX 100) and micromolecule surfactant (SDS and CTAB), the tendency of dynamic interfacial tension at the rupturing moment to decrease with increasing concentrations is contradicted. However, turning points are noted for the different surfactant systems. Using a particular curve to fit the experimental data, turning concentrations are determined to approximate CMC values. The results presented in this work provide a more in-depth understanding of the dynamic mass transfer of different surfactants outside the droplet during the formation of a droplet in microfluidic devices.

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