Creating Tunable Low-Surface-Tension-Liquid Capsules via Impact-Driven Liquid-Liquid Encapsulation.

Area of Science:

• Materials Science and Engineering
• Chemical Engineering
• Fluid Dynamics

Background:

• Encapsulation of low-surface-tension droplets is crucial for pharmaceuticals, environmental engineering, and thermal management.
• Impact-driven liquid-liquid encapsulation (LLE) is a promising but underexplored technique for droplet encapsulation.
• Controlled encapsulation of low-surface-tension droplets using impact-driven LLE has not been fundamentally investigated.

Purpose of the Study:

• To advance the ultrafast impact-driven LLE technique for the controlled encapsulation of low-surface-tension droplets.
• To experimentally investigate the fundamental mechanisms and parameters governing this encapsulation process.

Main Methods:

• Experimental demonstration of ultrafast impact-driven liquid-liquid encapsulation (LLE).
• Utilized FC-40 droplets (surface tension as low as 16 mN/m) with varying impact diameters (1.79–1.26 mm).
• Employed an ultrathin silicone oil interfacial (shell) layer and analyzed encapsulation regimes.

Main Results:

• Successfully encapsulated low-surface-tension FC-40 droplets within milliseconds.
• Identified three encapsulation regimes: interfacial trapping, penetration with air bubble, and penetration without air bubble.
• Demonstrated precise control over capsule morphology and size distribution by adjusting impact kinetic energy and interfacial layer thickness.

Conclusions:

• The study provides a fundamental understanding of impact-driven LLE for low-surface-tension droplets.
• Thicker interfacial layers promote air-bubble-free capsules.
• Offers valuable insights for efficient and cost-effective production of functional capsules in various applications.