Liquid Droplets Impacting on a Liquid Pool Covered with a Thin Polymeric Liquid Layer

In this study, we examine the process of filament thinning that occurs when a liquid droplet impacts a thin polymeric interfacial liquid layer floating in a water pool. We used partially cured polydimethylsiloxane solutions and polybutene gel mixed with polybutene liquid solutions in varying volumes for our experiments. The interfacial dynamics showed that the droplet drags the interfacial liquid into the pool, creating an air cavity, followed by its closer. Thereafter, a filament-thinning phase occurs. Initially, the thinning process was rapid due to crater interface retraction caused by the droplet impact. After the crater receded, a slender filament of the interfacial liquid remained, undergoing a slower thinning stage. This stage exhibited linear kinematics for Newtonian liquids (such as polydimethylsiloxane solution before the gel point transition) and exponential kinematics for viscoelastic liquids (such as polydimethylsiloxane solution during the gel point transition and polybutene solution). These findings improve our understanding of the interfacial dynamics in the liquid-liquid encapsulation process involving polymeric liquids, which are widely used commercially and in everyday life. This knowledge is vital for the process optimization and commercialization of this technique.