Bioactive templates fabricated by low-energy electron beam lithography of self-assembled monolayers

Adhesive templates for biomolecule patterning were fabricated on silicon and gold by low-voltage (1 kV) electron beam lithography of an inert self-assembled monolayer, followed by backfilling the exposed regions with an amine-terminated monolayer. Amine-terminated monolayers selectively attached either the desired materials or linker molecules that subsequently bound other materials including antibodies. Lines (300 nm wide) of 20-nm polystyrene beads were formed on gold by exposing a mercaptohexadecanoic acid (MHDA) monolayer, then backfilling with cysteamine, and selectively attaching aldehyde-coated beads to the amines. Attachment density was found to vary sharply around a critical dose, making the technique useful for patterns such as gradients which require varying density. An optimal dose of 200 μC/cm² was found for attaching fluorescent polystyrene spheres to MHDA-cysteamine templates. A cycling process was developed for aligning patterns of two or more kinds of polystyrene spheres. Biotin was tethered to the amine templates, making the technique applicable to high-resolution patterning of biomaterials with the widely used avidin-biotin binding system.