Liquid–liquid encapsulation with a constrained interfacial layer

The hydrophobic loop enabled stable confinement of denser interfacial liquids and produced visibly thicker lenses. The trapping-to-penetration transition boundary shifted upward with confinement, more strongly for smaller loops. Each loop exhibited a finite operable volume window. The thicker confined layers also reduced air entrapment by prolonging the residence time of the core droplet. Despite differences in geometry, the two loops showed similar transition Weber numbers at overflow, suggesting geometric similarity at the overflow limit. Overall, the loop enhances shell-liquid utilization, reduces air inclusion, and extends the versatility of liquid-liquid encapsulation.