Arrayed surfaces were fabricated using microcontact printing, as described previously [18]. In brief, we started with gold substrates (220 A on top of a 40 A Ti adhesion layer), deposited with an electron beam vapor deposition system (Thermionics, CA). Substrates were rinsed with 100% ethanol, and dried with a stream of nitrogen. Polydimethylsiloxane stamps were inked with octadecanethiol (10mM, Sigma, #74731) in ethanol, dried with a stream of nitrogen, and brought into contact with the clean gold for 1 minute. The printed gold was then cleaned with 100% ethanol, dried with nitrogen and backfilled in triethylene glycol mono-11-mercaptoundecyl ether (10 mM, Sigma, #673110) in ethanol overnight at 4°C. Surfaces were then rinsed well in 100% ethanol and dried with a stream of nitrogen for storage until use.
