(105c) Formation of Organosilane “Nano-Beaker” Arrays by Particle Lithography

The ability to make nano-arrays enables high-throughput screening and nanofluidics. This paper describes a simple method to make nano-arrays of organosilanes on oxidized silicon wafers based on latex particle lithography. Particle lithography was carried out on 300 and 900 nm polystyrene latex particle array templates by chemical vapor deposition (CVD) of octadecyltrichlorosilane (OTS). OTS reacts with the substrate in the water menisci in between latex particles to form a ring pattern. In order to use the ring pattern as “beakers” to contain droplets and particles, it is necessary to increase the OTS ring height beyond its monolayer thickness of 2.6 nm. We discovered CVD conditions that favor OTS bulk polymerization resulting in 14 nm thick rings for 900 nm particles and 9 nm thick rings for 300 nm particles. Mechanisms for the “nano-beaker” array formation were investigated. In addition, the use of OTS nano-arrays for distributing and containing solutions was demonstrated with hydrophobic compounds and nanoparticles. It is estimated that a 1×1 cm² wafer containing ordered “nano-beaker” arrays made with 900 nm particle lithography holds more than 100 million droplets with droplet volume less than 3×10^-10 nL. The OTS nano-arrays are stable against common solvents, which allow repeated use in high-throughput crystallization and confinement screening experiments.