Controlled vapor deposition approach to generating substrate surface energy/chemistry gradients

Substrate surface energy/chemistry gradients provide a means for high-throughput exploration of the surface interactions that are important in many chemical and biological processes. We describe the implementation of a controlled vapor deposition approach to surface modification that enables the facile production of substrate surface energy/chemistry gradients while maintaining versatility in both the gradient profile and the surface chemistry. In our system, gradient formation relies on the cross-deposition of functionalized chlorosilanes onto the substrate surface via vaporization of the deposition materials from liquid reservoirs under dynamic vacuum. The effects of liquid reservoir size (reservoir surface area), reservoir position relative to the substrate, vacuum application, and volatility of the deposition materials are examined in detail and demonstrate the level of gradient tunability afforded by this vapor deposition approach.