Double emulsions: a tool for probing thin-film metastability

Area of Science:

• Colloid and Interface Science
• Physical Chemistry
• Materials Science

Background:

• Double emulsions are complex multiphase systems with applications in food, pharmaceuticals, and cosmetics.
• Understanding droplet coalescence and release mechanisms is crucial for controlling emulsion stability and functionality.
• Previous studies have focused on emulsion formation and stability, with less emphasis on the release kinetics of internal droplets.

Purpose of the Study:

• To investigate the kinetics governing the release of internal aqueous droplets from water-in-oil-in-water (W/O/W) double emulsions.
• To directly measure the thin film lifetime between internal droplets and the external phase during coalescence.
• To determine the fundamental parameters of the hole nucleation process in adhesive thin liquid films.

Main Methods:

• Utilizing monodisperse W/O/W double emulsions.
• Measuring the rate of release of adsorbed internal droplets from the globule interface.
• Analyzing the dynamics of thin film rupture and droplet detachment.

Main Results:

• The rate of adsorbed droplet release was directly correlated with the thin film lifetime.
• The average lifetime of the thin film was accurately determined.
• Key parameters of the hole nucleation process, including activation energy and natural frequency, were unambiguously deduced.

Conclusions:

• The study provides direct insights into the mechanisms governing the release of internal droplets in W/O/W emulsions.
• The determined film lifetimes and nucleation parameters are essential for predicting and controlling emulsion stability.
• This research contributes to a deeper understanding of coalescence phenomena in complex fluid interfaces.