Photo-Responsive Fluorosurfactant Enabled by Plasmonic Nanoparticles for Light-Driven Droplet Manipulation.

The past decade has witnessed a significant development of droplet microfluidics for applications such as directed evolution and single-cell analysis. While the stability and manipulation of droplets are part of the prerequisites to further their applications, most of the currently available surfactants serve solely as stabilizers between the interfaces of water and oil. In this study, we present a novel type of photo-responsive fluorosurfactant based on fluorinated plasmonic nanoparticles (NPs). The demonstration by fluorinated gold-silica core-shell NPs (f-Au@SiO2) has been shown to be effective in stabilizing the water-in-fluorocarbon oil droplets. More importantly, the photothermal response enabled by the f-Au@SiO2 has been shown to be promising for the movement of droplets as well as the alteration of interfacial stability. The unique photo-responsiveness provided by the plasmonic NPs is expected to gear up the droplet microfluidics with an "active" surfactant for reconfigurable optical manipulation.