Nanotech 2011

Photolithographic Fabrication of Biomolecular Nanostructures (invited presentation)

G. Leggett
The University of Sheffield, UK

Keywords: biomolecular nanostructures, photolithography

Abstract:

The integration of top-down (lithographic) and bottom-up (synthetic) methodologies remains one of the most important unsolved problems in molecular nanoscience. Photochemistry is an attractive solution, because there is such a large catalogue of photochemical synthetic reactions to draw upon. The problem is to integrate this with nanometer scale spatial control of reactivity. We have addressed this with near-field optical techniques, which have enabled the nanopatterning of proteins and oligonucleotides. Using a scanning near-field optical microscope attached to a UV laser, we have fabricated structures as small as 9 nm in self-assembled monolayers of alkanethiols on gold. We have developed a diverse toolkit that enables the nanometer scale patterning of molecules on silicon, aluminum and titanium substrates, employing photochemical reactions in monolayers of silanes, phosphonic acids, polymers, fullerenes and metal nanoparticles. Using near-field techniques, proteins may be immobilized site-specifically, with full retention of biological function, in nanoscopic regions. We have adapted photochemical protecting group strategies from oligonucleotide synthesis, and for the first time integrated conventional synthetic chemical methodology into a nanofabrication system. The fabrication of molecular nanostructures over large areas has been addressed by blending near-field approaches with the concept of parallelism embodied in IBM’s Millipede. In a new device we call the “Snomipede”, parallel near-field probe arrays are excited using either a liquid crystal spatial light modulator or a Brewster angle zone plate array combined with a digital mirror device, providing individual control of writing by up to sixteen probes in parallel. The Snomipede can write molecular patterns with a line width of 125 nm over an area more than 1 mm wide in monolayers of aminosilanes, and has achieved features sizes of 70 nm in photoresist while operating with the entire probe array immersed under water, pointing the way to a future “reactive nanolithography”.
 

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