Droplet adsorption and enhancement at liquid-liquid interface: Effects of nanoparticle and surfactant

The droplet adsorption has many potential applications in microchemical engineering process, vesicle preparation and other various fields. However, the study on adsorption mechanisms and enhancement method remains still scarce so far. The droplet adsorption at the liquid–liquid interface relies primarily on the lubrication pressure in the liquid film, which determines the operating range of adsorption. The interaction between nanoparticles and surfactants distributed in two distinct phases could greatly affect the stability of the liquid film, thereby facilitating the droplet adsorption. In this study, a liquid–liquid–liquid three-phase system is constructed and the enhancement effect of interaction between nanoparticles and surfactants on the droplet interface adsorption process is visually investigated. The influences of the nanoparticle size on the interfacial dynamics and the operating range of droplet adsorption are studied systematically, and the adsorption and enhancement mechanisms are explored. It is found that the electrostatic interaction between PS-COOH NPs and PDMS could promote the rupture of the liquid film. The dense arrangement of nanoparticle-surfactant monolayer at the interface would hinder the evolution of the adsorption interface. Appropriate increase in the size of nanoparticles could facilitate the droplet adsorption process.