Silica nanoparticle-based coatings with superhydrophilic and superhydrophobic properties

Superhydrophilic and superhydrophobic surfaces have potential for implementation into a variety of fields, including self-cleaning surfaces, anti-fogging transparent materials, and biomedical applications. In this study, sandblasting, oxygen plasma treatments, silica nanoparticle films, and a low surface energy fluorocarbon film were employed to change the natural surface wettability of titanium, glass, and polyethylene terephthalate (PET) substrates, with an aim to produce superhydrophilic and superhydrophobic behavior. The effects of these surface modifications are characterized by water contact angles (WCAs), surface wetting stability, surface morphology and roughness, surface elemental composition, and optical transmittance measurements. The results show that stable superhydrophilic and superhydrophobic surfaces can be fabricated on titanium; stable superhydrophilic and unstable nearly superhydrophobic surfaces can be fabricated on glass; and very hydrophilic (WCA ∼ 10°) and very hydrophobic (WCA ∼ 135°) surfaces can be produced on PET. In addition, the silica nanoparticle films utilized have antireflective properties and increase optical transmittance of glass and PET substrates across the entire visible spectrum. This thesis provides a foundation for further studies into the implementation of these functional surfaces into practical applications, as well as a deeper understanding of how the properties (morphology, roughness, chemistry, etc.) of these modified surfaces influence their surface wetting properties.