Tribology and hydrophobicity of a biocompatible GPTMS/PFPE coating on Ti6Al4V surfaces

Effect of Heat Treatment on the Material Property and Cell Viability of Wire Arc Additively Manufactured Ti6Al4 V

Wire arc additive manufacturing (WAAM) holds promise for producing medium to large industrial components. Application of WAAM in the manufacturing of biomedical materials has not yet been evaluated. The current study addresses two key research questions: first, the suitability of the WAAMed Ti6Al4V alloy for biomedical applications, and second, the effect of Ti6Al4V's constituents (α and β phases) on the cell viability. The WAAMed Ti6Al4V alloy was fabricated (as-deposited: AD) using a metal inert gas (MIG)-based wire arc system using an in-house designed shielding chamber filled with argon. Subsequently, samples were subjected to solution treatment (950 °C for 1 h), followed by aging at 480 °C (T1), 530 °C (T2), and 580 °C (T3) for 8 h and subsequent normalization to ambient conditions. Microstructural analysis revealed ∼45.45% of α'-Ti colonies in the as-deposited samples, reducing to 23.26% postaging at 580 °C (T3). The α-lath thickness and interstitial oxygen content in the sample were observed to be proportional to the aging temperature, peaking at 580 °C (T3). Remarkably, during tribocorrosion analysis in simulated body fluid, the 580 °C-aged T3 sample displayed the lowest corrosion rate (7.9 μm/year) and the highest coefficient of friction (CoF) at 0.58, showing the effect of increasing oxygen content in the alloy matrix. Cell studies showed significant growth at 530 and 580 °C by day 7, correlated with higher oxygen content, while other samples had declining cell density. Additionally, optimal metallurgical property ranges were identified to enhance the Ti6Al4V alloy's biocompatibility, providing crucial insights for biomedical implant development.

Tribological Properties of Ti6Al4V Alloy Composite Texture Fabricated by Ultrasonic Strengthening Grinding and Laser Processing

The Ti6Al4V alloy has been widely used in aerospace equipment and medical devices. However, the poor wear resistance of the Ti6Al4V alloy hinders its further engineering application. In this study, the ultrasonic strengthening grinding process (USGP) and laser texturing process were employed to enhance the wear resistance of Ti6Al4V alloy. The frictional behavior of all samples was determined via a ball-on-disc friction and wear tester under dry conditions. The worn surface morphology, cross-sectional hardness, surface roughness, and microstructure were analyzed. The results demonstrated that the USGP induced high hardness, high dislocation density, and grain refinement, as well as improvements in the wear resistance of Ti6Al4V. Moreover, laser texture could enhance the capacity to capture wear debris and reduce wear probability. When combining the USGP and laser texturing process for the surface treatment of Ti6Al4V alloy, the lowest and most stable friction coefficients were obtained, as well as the best wear resistance. Compared to the polished sample, the steady stage friction coefficient of the sample treated by USGP and laser texturing process was remarkably decreased by 58%. This work demonstrates that combining the USGP and laser texturing process could be a promising solution for improving the wear resistance properties of Ti6Al4V alloy, which makes it more suitable for various engineering applications.

Enhancing Mechanical Properties and Biological Performances of Injectable Bioactive Glass by Gelatin and Chitosan for Bone Small Defect Repair

Bioactive glass (BG) represents a promising biomaterial for bone healing; here injectable BG pastes biological properties were improved by the addition of gelatin or chitosan, as well as mechanical resistance was enhanced by adding 10 or 20 wt% 3-Glycidyloxypropyl trimethoxysilane (GPTMS) cross-linker. Composite pastes exhibited bioactivity as apatite formation was observed by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) after 14 days immersion in simulated body fluid (SBF); moreover, polymers did not enhance degradability as weight loss was >10% after 30 days in physiological conditions. BG-gelatin-20 wt% GPTMS composites demonstrated the highest compressive strength (4.8 ± 0.5 MPa) in comparison with the bulk control paste made of 100% BG in water (1.9 ± 0.1 MPa). Cytocompatibility was demonstrated towards human mesenchymal stem cells (hMSC), osteoblasts progenitors, and endothelial cells. The presence of 20 wt% GPTMS conferred antibacterial properties thus inhibiting the joint pathogens Staphylococcus aureus and Staphylococcus epidermidis infection. Finally, hMSC osteogenesis was successfully supported in a 3D model as demonstrated by alkaline phosphatase release and osteogenic genes expression.

Multifaceted aspects of charge transfer

Charge transfer and charge transport are by far among the most important processes for sustaining life on Earth and for making our modern ways of living possible. Involving multiple electron-transfer steps, photosynthesis and cellular respiration have been principally responsible for managing the energy flow in the biosphere of our planet since the Great Oxygen Event. It is impossible to imagine living organisms without charge transport mediated by ion channels, or electron and proton transfer mediated by redox enzymes. Concurrently, transfer and transport of electrons and holes drive the functionalities of electronic and photonic devices that are intricate for our lives. While fueling advances in engineering, charge-transfer science has established itself as an important independent field, originating from physical chemistry and chemical physics, focusing on paradigms from biology, and gaining momentum from solar-energy research. Here, we review the fundamental concepts of charge transfer, and outline its core role in a broad range of unrelated fields, such as medicine, environmental science, catalysis, electronics and photonics. The ubiquitous nature of dipoles, for example, sets demands on deepening the understanding of how localized electric fields affect charge transfer. Charge-transfer electrets, thus, prove important for advancing the field and for interfacing fundamental science with engineering. Synergy between the vastly different aspects of charge-transfer science sets the stage for the broad global impacts that the advances in this field have.

Challenges and developments of self-assembled monolayers and polymer brushes as a green lubrication solution for tribological applications

Surface initiated polymer brushes, grafted from self-assembled initiating monolayers on a contact surface, provide opportunities to develop innovative solutions for friction reduction in tribological systems.