Water-oil Janus emulsions: microfluidic synthesis and morphology design

Area of Science:

• Colloid and Surface Science
• Microfluidics
• Materials Science

Background:

• Janus emulsions, particles with distinct properties on each hemisphere, are valuable in various applications.
• Controlling the morphology of Janus emulsions is challenging but essential for tailored functionalities.
• Microfluidic devices offer precise control over droplet formation and manipulation.

Purpose of the Study:

• To develop a facile and in situ method for preparing water-oil Janus emulsions with tunable morphologies.
• To propose a predictive model for designing Janus emulsion morphologies based on fluid properties and interfacial tensions.
• To explore the influence of flow rate and surfactant concentration on Janus emulsion formation and shape.

Main Methods:

• Utilized a double-bore capillary microfluidic device for simultaneous introduction of water and oil phases.
• Employed a theoretical model combined with fluid properties to guide the design of Janus emulsion morphologies.
• Systematically varied surfactant mass fraction in the continuous phase to tune interfacial tensions.
• Adjusted the flow rate ratio between the water and oil phases to control droplet formation.

Main Results:

• Successfully prepared water-oil Janus emulsions with tunable morphologies in situ.
• Demonstrated a method to design Janus emulsion morphology by controlling interfacial tension and flow ratio.
• Achieved gradual changes in Janus morphology by systematically adjusting surfactant concentration and flow rate.
• Prepared Janus emulsions across a wide range of flow ratios.

Conclusions:

• The developed microfluidic method provides facile and precise control over water-oil Janus emulsion morphology.
• The combination of a theoretical model and fluid property analysis enables predictable design of Janus emulsion shapes.
• This technique is highly relevant for applications requiring precisely engineered amphiphilic Janus particles.