Wettability changes of TiO2 nanotube surfaces

This study examines the effect of environmental and experimental conditions, such as temperature and time, on the wettability properties of titania nanotube (TNT) surfaces fabricated by anodization. The fabricated TNTs are 60-130 nm inner diameter and 7-10 µm height. One-microliter water droplets were used to define the wettability of the TNT surfaces by measuring the contact angles. A digital image analysis algorithm was developed to obtain contact angles, contact radii and center heights of the droplets on the TNT surfaces. Bare titanium foil is inherently less hydrophilic with approximately 60°-80° contact angle. The as-anodized TNT surfaces are more hydrophilic and annealing further increases this hydrophilic property. Furthermore, it was found that the TNT surface became more hydrophobic when aged in air over a period of three months. It is believed that the surface wettability can be changed due to alkane contamination and organic contaminants in an ambient atmosphere. This work can provide guidelines to better specify the environmental conditions that changes surface properties of TNT surfaces and therefore affect their desirable function in specific applications such as orthopedic implants.