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

Area of Science:

• Fluid Dynamics
• Polymer Science
• Interfacial Phenomena

Background:

• Liquid-liquid encapsulation is crucial for various commercial applications.
• Understanding interfacial dynamics during droplet impact is key to process optimization.
• Polymeric liquids exhibit complex behaviors, including viscoelasticity, affecting encapsulation.

Purpose of the Study:

• To investigate the filament thinning process after a liquid droplet impacts a polymeric interfacial liquid layer.
• To differentiate the thinning kinematics between Newtonian and viscoelastic liquids.
• To enhance comprehension of liquid-liquid encapsulation dynamics.

Main Methods:

• Experiments were conducted using partially cured polydimethylsiloxane solutions and polybutene gel/liquid mixtures.
• Interfacial dynamics were observed following droplet impact on a floating interfacial liquid layer.
• Kinematics of filament thinning were analyzed for Newtonian and viscoelastic fluid behaviors.

Main Results:

• Droplet impact initially creates an air cavity, followed by filament thinning.
• Initial rapid thinning is attributed to crater retraction, succeeded by a slower thinning phase.
• Newtonian liquids displayed linear thinning kinematics, while viscoelastic liquids showed exponential kinematics.

Conclusions:

• The study elucidates distinct filament thinning behaviors in liquid-liquid encapsulation based on fluid properties.
• Findings provide critical insights into the dynamics of polymeric interfacial layers during droplet impact.
• This knowledge is vital for optimizing and commercializing liquid-liquid encapsulation techniques.