Investigation of static and dynamic wetting transitions of UV responsive tunable wetting surfaces

摘要

Ultraviolet (UV) radiation responsive surfaces, with tunable wetting properties, are fabricated by spin casting polystyrene/titania nanocomposite dispersion in tetrahydrofuran on silicon substrates. The prepared samples are found hydrophilic due to the presence of the water miscible solvent. Upon annealing, as the solvent evaporates, samples become superhydrophobic due to presence of hydrophobic polystyrene and formation of nano and micro scale surface roughness due to titania nanoparticles. Effect of different annealing temperatures and time on resulting wettability is investigated. Photocatalytic property of titania is exploited to make transition from superhydrophobic to hydrophilic state upon UV exposure. Subsequently, upon annealing again at elevated temperatures for sufficient time, the UV exposed hydrophilic samples recover their superhydrophobicity showing transition from hydrophilic to superhydrophobic state. Detailed static and dynamic study of these reversible transitions, between superhydrophobic and hydrophilic states, due to UV exposure and annealing is presented in this article.