| Abstract: |
Chemical surface patterning at the nanoscale is an important component of the chemically directed assembly of sensitive biological molecules or nanoscale electrical devices onto surfaces. Here we present a scanning probe lithography technique that allows for patterning of aqueous polymers on glass or silicon dioxide surfaces. The surfaces were functionalized by covalently bonding a silane monolayer with a known surface charge to either a borosilicate glass slide or thermal oxide on a silicon wafer. A polymer layer less than 2 nm in thickness was then electrostatically bound to the silane layer, passivating the functionalized surface. An Atomic Force Microscope (AFM) probe was used to mechanically remove a portion of the polymer layer, exposing the functional silane layer underneath. Employing this method we made chemically active submicron regions. These regions were backfilled with a fluorescently-tagged polymer. Chemical differentiation was verified through tapping mode AFM and optical fluorescence microscopy. Lines with a pitch as small as 20 nm were observed with AFM height and phase mode data. Scribing forces were measured as low as 0.3 μN. Scribing was successful in ambient conditions as well as in aqueous solution, thus allowing patterning of sensitive biological molecules in their native environments. No instabilities in the created patterns were noted during observation periods of several months. |