Roughness-dependent hydrophobicity of polydimethylsiloxane grafted titanium thin films

Abstract

Understanding the wetting behavior of thin films is essential for advanced coatings applications. This paper studies the roughness dependent hydrophobicity of titanium thin films deposited by radio frequency magnetron sputtering. The grafting of mechanochemically activated polydimethylsiloxane (PDMS) onto a titanium thin film is achieved by benefiting from the self-formation of an oxide layer during the sputter-coating process. PDMS grafting results in a liquid-like hydrophobic layer with a nanoscopic (<3 nm) thickness, which makes it possible to investigate the roughness dependent wetting behavior of titanium films. In addition to the structural characterization, atomic force microscopy imaging was used to derive different morphological parameters. Correlating static and dynamic water contact angle measurements with these morphological parameters enabled identification of different wetting states. The findings of this study contribute to the design and fabrication of stochastically structured hydrophobic surfaces with a stable wetting state that is needed in practical applications.