Wettability changes of TiO₂nanotube surfaces

Abstract

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.

Wettability studies of topologically distinct titanium surfaces

“…Studies demonstrate that the nanoscale morphologies display different wettability behaviour as compared to their microscale counterparts. 40,41 In general, the physics of liquid droplet interactions with nanostructured 40 and microstructured 41 surfaces have been the subject of increasing interest in the past few years.…”

“…40,42,43 For example by the aid of plasma treatment technique, the hydrophobic character of aged TiO 2 nanopore/nanotube surface will be reversed to hydrophilic, possibly due to the removal of surface contaminants, such as carbon. It was shown recently that wettability of TiO 2 nanosurfaces can change with time.…”

Biophysical evaluation of cells on nanotubular surfaces: the effects of atomic ordering and chemistry

“…44 After the anodization process, the droplet contact angles decreased in the range of 55%~70% compared to the bare substrate. This indicates that the creation of nanotube structures makes the surface more hydrophilic.…”

“…The rationale behind such a conclusion is that nanotube surfaces enhance surface energy as well as hydrophilicity of the surface due to the presence of functional hydroxyl groups on the surface. 44 Considering that proteins are better absorbed on the hydrophilic TiO 2 nanotube surfaces, cell adhesion is enhanced. This hypothesis is in agreement with Yao et al's study 46 which reported that the initial adsorption of proteins on anodized nanotube Ti was increased compared to anodized nanoparticles and un-anodized Ti.…”

Transparent TiO2 nanotubes on zirconia for biomedical applications

“…[18][19][20][21] TNTs also improve the physiochemical characteristics of surfaces as shown through their ability to maintain surface wettability for a period of at least one month compared to smooth or rough Ti surfaces. [22][23][24] Hydrophilic surfaces attract more bronectin (FN) and vitronectin (VN) protein from the body uids, which are essential sites for cellular attachment and proliferation.…”