A novel approach to produce biologically relevant chemical patterns at the nanometer scale: Selective molecular assembly patterning combined with colloidal lithography

A novel patterning technique that combines colloidal patterning with selective adsorption of organic molecules has been used to chemically pattern metal oxide surfaces at length scales down to 50 nun. Lithographic nanofabrication using surface-assembled colloids as etch masks ("colloidal lithography") was used to create nanopillars of TiO2 (50-90 nm in diameter, similar to20 nm in height) on whole oxidized silicon or quartz wafer substrates. These nanopillars were then rendered hydrophobic by the selective self-assembly of an organophosphate, whereas a poly(ethylene glycol)-grafted copolymer was adsorbed onto the surrounding SiO2 rendering it protein resistant. This resulted in a two-component chemical pattern, displaying contrast with respect to protein adsorption (protein-adhesive pillars on nonadsorbing background). This property allows for efficient translation of the lithographic pattern into a surface protein pattern by two simple dip-and-rinse processes in aqueous solutions. The feasibility of the method and its quality were tested by adsorbing fluorescently labeled streptavidin and biotinylated phospholipid vesicles. The sequential adsorption steps were monitored by fluorescence microscopy, atomic force microscopy, and scanning near-field optical microscopy. These techniques conclusively demonstrated the utility of the described approach for chemical patterning surfaces on the nanometer scale over large areas.