Surface nanodroplets as platforms for small scale chemical engineering

Intensification of chemical process by compartmentalization has been a topic of interest as it may make the process faster and more energy efficient. Performing chemical reactions in confinement offers advantages from faster kinetics, mild reaction conditions, higher reaction efficiency, low consumption of reagents, and higher selectivity of products. Microdroplets immersed in immiscible fluids may serve as confining environment in which chemical reactions take place. Particular attention has been paid to femtoliter droplets formed on a surface – termed as surface nanodroplets – which can be harnessed as stable confinement for chemical reaction. Recently, surface nanodroplets have been intensively studied from basic formation mechanism to their applications in chemical sensing, liquid–liquid extraction, and optical focusing. As small-scale chemical reactors, the liquid composition in surface nanodroplets can be tuned to enable investigation of biphasic reaction kinetics, synthesis of new materials, and enhanced photocatalysis. In this review, the author intends to highlight some of the latest achievements on surface nanodroplets as reactors in confinement and point out the potential of integrating robotic and machine learning technology in small scale chemical engineering.