Antibacterial properties are critical for implants, while general pure titanium implants are bioinert. Adding nano Ag to metals is an effective strategy to obtain antibacterial properties. However, the comprehensive properties of Ti–Ag alloy prepared by traditional methods are not satisfactory. In this paper, Ti–5Ag alloy with an antibacterial rate close to 100 % was synthesized in situ by laser powder bed fusion (LPBF), and its microstructure and properties were studied systematically. Phase analysis demonstrated the existence of Ti2Ag which played an important role in gaining excellent antibacterial properties. Benefiting from in situ laser alloying, the elements were homogeneously distributed, which endowed the Ti–5Ag alloy with excellent mechanical properties and corrosion resistance. The tensile strength and elongation reached 716 MPa and 33.51 %, respectively. Furthermore, through the design of triply periodic minimal surface (TPMS) structures, mechanical properties matching human bone were obtained. Based on LPBF-printed Ti–5Ag alloy and TPMS structures, this paper provides a feasible method for the manufacturing of bone implants with excellent comprehensive properties.
The porous structure design of implants can not only obtain a more lightweight implant but also provide more space for its cell growth. The technology development of additive manufacturing (AM) offers an effective way for customized porous implants. To explore the suitable porous titanium bone implants made by AM, this paper reviews the research progress in the designing and manufacturing performance of porous titanium alloy implants, which are manufactured by AM. The design parameters that affect the bone ingrowth performance are analyzed, including the porosity, shape, and aperture of the pore. Based on the current technology trend, the future development of bone implants in advanced multi-materials, design methods, and post-treatment methods is prospected.
Regeneration of large-sized cartilage injury is a challenging endeavor. In vitro bioprinting for cartilage repair has several drawbacks, such as the tedious process of material preparation, potential contamination, and the mismatch between implant and defect. This study aimed to investigate the application of in situ bioprinting in cartilage repair using a parallel manipulator. In particular, the material extrusion rate and printing speed were adjusted to obtain the suitable forming parameters in a custom-made parallel manipulator. Cell experiments were conducted to determine the biocompatibility. Finally, a rabbit cartilage defect model was used to evaluate the feasibility of in situ bioprinting combined with machine vision. The results showed that to achieve optimum printing using the custom-made three-dimensional printer, 400–560 mm/min should be set as the standard printing speed, with an extrusion multiplier of 0.09–0.10. Cartilage defects can be precisely and easily segmented using a bimodal method with a 2% deviation error. In vitro experiments revealed that the utilized materials are highly biocompatible. Furthermore, according to the results from in vivo experiments, in situ bioprinting lends itself useful in the repair of cartilage defects. The overall results confirmed the feasibility of applying a parallel manipulator in in situ bioprinting for cartilage repair. Additional optimizations of the proposed approach are warranted prior to translation into clinical applications in the future.
Remelting has a significant effect on controlling microstructure and enhancing properties of components prepared by laser powder bed fusion. In order to reveal the mechanism of the effect of remelting time intervals, this study employed a dual-laser powder bed fusion equipment to ensure precise and controllable time intervals of remelting. The effects of intervals (2 ms, 5 ms, and 50 ms) on substructure morphology, microstructure and mechanical properties of 316L were analyzed. The results indicate that the grain size ranged from 13.03 μm to 26.55 μm due to the influence of initial temperature at different remelting intervals on grain size. Additionally, the composition ratio between columnar and cellular substructure varies with the time interval, which greatly influences mechanical properties. Longer intervals favor columnar substructures in high-temperature gradients, and dislocation motion is impeded, leading to an increased strength of up to 689.6 MPa. Shorter intervals promote cellular substructures in low-temperature gradients, and dislocations move smoothly along the boundaries of substructure, leading to an elongation of up to 49.3 %. Therefore, a novel method for controlling microstructure and properties is provided in this study utilizing the precise controllable remelting time intervals of dual-laser powder bed fusion.
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