Microscale plasma-initiated patterning (μPIP)

A novel technique to create biomolecular micropatterns of varying complexity on several types of polymer 144 substrates is presented. This method uses a patterned PDMS stamp to preferentially expose or protect areas of an underlying polymer substrate from oxygen plasma. Following plasma treatment, the substrate is immersed in a biomolecular ink, whereby molecules preferentially adsorb to either the plasma-exposed or plasma-protected substrate regions, depending on the particular substrate/ink combination. Using this method, polyethylene (PE), polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(dimethylsiloxane) (PDMS), and poly(hydroxybutyrate/hydroxyvalerate) (PHBV) were micropatterned with different aqueous based biomolecular inks (i.e., goat anti-rabbit immunoglobulin G, poly-L-lysine, and bovine serum albumin (BSA)). Water contact angle measurements performed on substrates after oxygen plasma exposure showed that the hydrophilicity of substrate areas exposed to plasma was significantly greater than that of areas protected from plasma by the PDMS stamp. In addition, scanning electron microscopy results demonstrated that substrate areas exposed to plasma were physically modified (e.g., roughened) compared to adjacent, protected areas. Areas in contact with a patterned PDMS stamp during plasma exposure were found to be physically unaffected by plasma treatment, and exhibited spatial features/dimensions consistent with the corresponding features of the patterned stamp. Last, protein patterns of BSA on the polymer substrates were stable and distinct after 4 weeks of incubation at 37 degrees C.