Cluster-assembled nanostructured titanium oxide films with tailored wettability

We report on the production of cluster-assembled nanostructured titanium oxide (ns-TiOx) surfaces with tailored wettability properties. The contact angle of the ns-TiOx surfaces changes in a controllable and reproducible way by changing the morphology through the roughness and/or with annealing the films in air at different temperatures. With increasing the annealing temperature, reversible switching from hydrophobic to hydrophilic behavior can be obtained, due to the removal of organic contaminants and to the increase of surface hydroxyl groups, while control of surface morphology allows fine-tuning of the contact angle within a given wetting regime. Thanks to the possibility of regulating and controlling the surface wettability, ns-TiOx thin films are very promising substrates for protein microarray applications where a reproducible control on protein spot dimension is required.