Nanolayer Laser Absorber for Femtoliter Chemistry in Polymer Reactors

Laser-induced forward transfer (LIFT) has the potential to be an alternative approach to atomic force microscopy based scanning probe lithography techniques, which have limitations in high-speed and large-scale patterning. However, traditional donor slides limit the resolution and chemical flexibility of LIFT. Here, a hematite nanolayer absorber for donor slides to achieve high-resolution transfers down to sub-femtoliters is proposed. Being wettable by both aqueous and organic solvents, this new donor significantly increases the chemical scope for the LIFT process. For parallel amino acid coupling reactions, the patterning resolution can now be increased more than five times (>111 000 spots cm^{- 2} for hematite donor vs 20 000 spots cm^{- 2} for standard polyimide donor) with even faster scanning (2 vs 6 ms per spot). Due to the increased chemical flexibility, other types of reactions inside ultrasmall polymer reactors: copper (I) catalyzed click chemistry and laser-driven oxidation of a tetrahydroisoquinoline derivative, suggesting the potential of LIFT for both deposition of chemicals, and laser-driven photochemical synthesis in femtoliters within milliseconds can be explored. Since the hematite shows no damage after typical laser transfer, donors can be regenerated by heat treatment. These findings will transform the LIFT process into an automatable, precise, and highly efficient technology for high-throughput femtoliter chemistry.