Microfluidic formation of surface nanodroplets using green deep eutectic solvents for liquid-liquid nanoextraction and controlled precipitation.

The formation of gDES surface nanodroplets follows the theoretical model which states that the final droplet volume (V) scales with the Peclét number (Pe) of the flow during formation by the solvent exchange process, that is V ∼ Pe, and the nanodroplets demonstrate excellent ability as extractant for rhodamine 6G and copper ions from water. Surprisingly, the confined volume of gDES surface nanodroplets enables fast and controlled formation of Cu (II)-decanoate crystal.