Programmable wettability on photocontrolled graphene film.

Surface materials with specific wettability play important roles in a wide variety of areas from science to industry. We present a novel paraffin-infused porous graphene film (PIPGF) with programmable wettability. Because of graphene's photothermal property, the paraffin in the PIPGF was in transition between liquid and solid in response to near-infrared (NIR) light irradiation. Thus, we imparted the film with a dynamic and reversible transition between a slippery and a rough surface as the remotely tunable wettability. In addition, with the integration of NIR masks, the paraffin could melt at corresponding patterns on the PIPGF, which formed special flow pathways for the slipping droplets. Therefore, the PIPGF could provide programmable wettability pathways for the spatiotemporal droplet manipulation by flexibly changing the NIR masks. We demonstrated these programmable wettability pathways to not only simplify liquid handling in the microplates and droplet microarrays technology but also to provide distinctly microfluidic microreactors for different purposes, such as practical blood grouping diagnosis. These features indicated that the photocontrollable PIPGF would be amenable to a variety of applications, such as microfluidic systems, laboratory-on-a-chip settings, and droplet manipulations.