Yuebin Lin

Titanium and its alloys are widely used in blood-contacting implantable and interventional medical devices; however, their biocompatibility is still facing great challenges. In the present study, in order to improve the biocompatibility and antibacterial activities of titanium, TiO₂ nanotubes were firstly in situ prepared on the titanium surface by anodization, followed by the introduction of polyacrylic acid (PAA) and gentamicin (GS) on the nanotube surface by layer-by-layer assembly, and finally, zinc ions were loaded on the surface to further improve the bioactivities. The nanotubes displayed excellent hydrophilicity and special nanotube-like structure, which can selectively promote the albumin adsorption, enhance the blood compatibility, and promote the growth of endothelial cells to some degree. After the introduction of PAA and GS, although the superhydrophilicity cannot be achieved, the results of platelet adhesion, cyclic guanosine monophosphate (cGMP) activity, hemolysis rate, and activated partial thromboplastin time (APTT) showed that the blood compatibility was improved, and the blood compatibility was further enhanced after zinc ion loading. On the other hand, the modified surface showed good cytocompatibility to endothelial cells. The introduction of PAA and zinc ions not only promoted the adhesion and proliferation of endothelial cells but also upregulated expression of vascular endothelial growth factor (VEGF) and nitric oxide (NO). The slow and continuous release of GS and Zn²⁺ over 14 days can significantly improve the antibacterial properties. Therefore, the present study provides an effective method for the surface modification of titanium-based blood-contacting materials to simultaneously endow with good blood compatibility, endothelial growth behaviors, and antibacterial properties.

Aircraft icing refers to ice formation and accumulation on the windward surface of aircrafts. It is mainly caused by the striking of unstable supercooled water droplets suspended in clouds onto a solid surface. Aircraft icing poses an increasing threat to the safety of flight due to the damage of aerodynamic shape. This review article provides a comprehensive understanding of the preparation and anti-icing applications of the superhydrophobic coatings applied on the surface of aircrafts. The first section introduces the hazards of aircraft icing and the underlying formation mechanisms of ice on the surface of aircrafts. Although some current anti-icing and de-icing strategies have been confirmed to be effective, they consume higher energy and lead to some fatigue damages to the substrate materials. Considering the icing process, the functional coatings similar to lotus leaf with extreme water repellency and unusual self-cleaning properties have been proposed and are expected to reduce the relied degree on traditional de-icing approaches and even to replace them in near future. The following sections mainly discuss the current research progress on the wetting theories of superhydrophobicity and main methods to prepare superhydrophobic coatings. Furthermore, based on the bouncing capacity of impact droplets, the dynamic water repellency of superhydrophobic coatings is discussed as the third evaluated parameter. It is crucial to anti-icing applications because it describes the ability of droplets to rapidly bounce off before freezing. Subsequently, current studies on the application of anti-icing superhydrophobic coatings including the anti-icing mechanisms and application status are introduced in detail. Finally, some limitations and issues related to the anti-icing applications are proposed to provide a future outlook on investigations of the superhydrophobic anti-icing coatings.

Owing to excellent mechanical property and biodegradation, magnesium-based alloys have been widely investigated for temporary implants such as cardiovascular stent and bone graft; however, the fast biodegradation in physiological environment and the limited surface biocompatibility hinder their clinical applications. In the present study, magnesium alloy was treated by sodium hydroxide (NaOH) and hydrogen fluoride (HF) solutions, respectively, to produce the chemical conversion layers with the aim of improving the corrosion resistance and biocompatibility. The results of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) indicated that the chemical conversion layers of magnesium hydroxide or magnesium fluoride were obtained successfully. Sodium hydroxide treatment can significantly enhance the surface hydrophilicity while hydrogen fluoride treatment improved the surface hydrophobicity. Both the chemical conversion layers can obviously improve the corrosion resistance of the pristine magnesium alloy. Due to the hydrophobicity of magnesium fluoride, HF-treated magnesium alloy showed the relative better corrosion resistance than that of NaOH-treated substrate. According to the results of hemolysis assay and platelet adhesion, the chemical surface modified samples exhibited improved blood compatibility as compared to the pristine magnesium alloy. Furthermore, the chemical surface modified samples improved cytocompatibility to endothelial cells, the cells had better cell adhesion and proliferative profiles on the modified surfaces. Due to the excellent hydrophilicity, the NaOH-treated substrate displayed better blood compatibility and cytocompatibility to endothelial cells than that of HF-treated sample. It was considered that the method of the present study can be used for the surface modification of the magnesium alloy to enhance the corrosion resistance and biocompatibility.

The Al layer with α-Al ₂ O ₃ seed crystals and the rare earth element Y were deposited directly onto a 316L stainless steel substrate and then oxidized at a temperature as low as 580°C using the double glow plasma technique. The complex Al target material containing 10 wt% α-Al ₂ O ₃ seed crystals and 10 wt% Y was used in the experiment. The results indicated that the coatings were very dense and uniform. The field emission transmission electron microscopy observation indicated that element Y was discontinuously distributed, which was mainly concentrated at the grain boundary of the coating. After plasma oxidation, Y was oxidized to Y ₂ O ₃ . Under the action of coupled multiple factors (ion bombardment, α-Al ₂ O ₃ seed crystals, and rare earth element Y), the AlYα oxide coatings contained large amounts of α-Al ₂ O ₃ crystals. The increase of the Y content improved the adhesive force of the coatings. The corrosion current of the oxide coatings was reduced by three orders of magnitude.

In this study, the plasma oxidation mechanism of aluminium (Al) coatings was studied by experimental and theoretical methods. Two alumina coatings prepared by thermal oxidation or plasma oxidation treatment were characterised by the energy-dispersive X-ray spectroscopy line-scan analysis. It was found that the sample treated by plasma oxidation had a peak curve of the O²⁻ ions at a depth of 0·7 μm. This phenomenon indicated that high-energy O²⁻ ions could be injected into the inner part of the coatings. The distribution and diffusion of O²⁻ ions in Al coatings were investigated by computer simulation using the Stopping and Range of Ions in Matter (SRIM) software and the first principles of molecular dynamics-based calculations. The experimental results of the distribution of O²⁻ ions agreed with those calculated by the SRIM software, which proved that the range of O²⁻ ion concentrations in the Al coatings was proportional to the energy of the O²⁻ ions. Through simulations of the Vienna Ab-Initio Simulation Package, it was shown that the inserted O²⁻ ions moved back and forth nearby the original location if there were no other Al vacancies available and the diffusion mechanism of oxygen was vacancy diffusion.