Complex Suspended Janus Droplets Constructed through Solvent Evaporation-Induced Phase Separation at the Air-Liquid...

Area of Science:

• Materials Science
• Physical Chemistry
• Surface Science

Background:

• Phase separation is a key phenomenon in materials science, extensively studied in emulsions and non-continuous environments.
• However, phase separation and spreading behavior of droplets at the air-liquid interface remain underexplored.
• Understanding these processes is crucial for developing novel materials and processes.

Purpose of the Study:

• To investigate phase separation phenomena and spreading behavior of suspended droplets at the air-liquid interface.
• To develop a novel strategy for creating suspended Janus droplets with controllable morphologies.
• To explore the potential applications of these droplets in material synthesis.

Main Methods:

• Utilized solvent evaporation-induced droplet phase separation to produce PEGDA-glycerol suspended Janus droplets.
• Varied glycerol/PEGDA volume ratio, ethanol proportion, and surfactant concentration to control droplet morphology.
• Developed and verified a modified spreading coefficient theory to explain air-droplet interface phase separation.

Main Results:

• Successfully produced various suspended droplet morphologies, including filbert-shaped, lotus seedpod-shaped, and multiple-bulge droplets.
• Generated a patchy structure at the air-droplet interface attributed to Marangoni stresses from nonuniform evaporation.
• Demonstrated the ability to control droplet suspension through interfacial tensions and equilibrium contact angles.

Conclusions:

• Developed a simple and versatile strategy for creating suspended Janus droplets at the air-liquid interface for the first time.
• The modified spreading coefficient theory successfully predicts phase separation at the air-liquid interface.
• This technique offers significant potential for material synthesis applications, including electrospinning.