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.

In lithium–oxygen batteries, the solubility of LiO2 intermediates in the electrolyte regulates the formation routes of the Li2O2 discharge product. High-donor-number electrolytes with a high solubility of LiO2 tend to promote the formation of Li2O2 large particles following the solution route, which eventually benefits the cell capacity and cycle life. Here, we propose that facet engineering of cathode catalysts could be another direction in tuning the formation routes of Li2O2. In this work, β-MnO2 crystals with high occupancies of {111} or {100} facets were adopted as cathode catalysts in Li–O2 batteries with a tetra­(ethylene)­glycol dimethyl ether electrolyte. The {111}-dominated β-MnO2 catalyzed the formation of the Li2O2 discharge product into large toroids following the solution routes, while {100}-dominated β-MnO2 facilitated the formation of Li2O2 thin films through the surface routes. Further computational studies indicate that the different formation routes of Li2O2 could be related to different adsorption energies of LiO2 on the two facets of β-MnO2. Our results demonstrate that facet engineering of cathode catalysts could be a new way to tune the formation route of Li2O2 in a low-donor-number electrolyte. We anticipate that this new finding would offer more choices for the design of lithium–oxygen batteries with high capacities and ultimately a long cycle life.

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The mechanical compressive properties of individual thin-wall and thick-wall TiO(2) nanotubes were directly measured for the first time. Nanotubes with outside diameters of 75 and 110 nm and wall thicknesses of 5 and 15 nm, respectively, were axially compressed inside a 400 keV high-resolution transmission electron microscope (TEM) using a new fully integrated TEM-atomic force microscope (AFM) piezo-driven fixture for continuous recording of the force-displacement curves. Individual nanotubes were directly subjected to compressive loading. We found that the Young's modulus of titanium dioxide nanotubes depended on the diameter and wall thickness of the nanotube and is in the range of 23-44 GPa. The thin-wall nanotubes collapsed at approximately 1.0 to 1.2 microN during axial compression.

Techniques for titanium surface modification have been studied for applications in orthopedic implants specifically for local drug delivery. The extensive research in surface modification is driving the development of devices that integrate infection prevention, osseointegration, and functionality in a structural role. In this study, vancomycin was applied to modified titanium surfaces to determine the effect of surface morphology on drug loading and release profiles. The antimicrobial effectiveness of the released vancomycin was evaluated and found to have a similar effect as the standard vancomycin. The engineered surfaces included sandblasted, sandblasted acid etched, electrochemically etched, and sandblasted electrochemically etched. The antibiotic release was observed to be independent of the measured surface parameters of the engineered surfaces. The development of an implantable device in which the surface morphology can be tailored for an application with no effect on the total drug released would be beneficial to more precisely control the biological response while maintaining local drug delivery for infection prevention.