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Biodegradable metals (BM) and additive manufacturing (AM) are regarded revolutionary biomaterials and biofabrication technologies for bone repairing metal implants, the combination of both, namely AM of BM, is thus expected to solve the dual technical difficulties including "conventional medical metals are biologically inert and exist in the human body permanently" and "conventional manufacturing processes are inadequate to fabricate personalized implants of complicated structure". This work additively manufactured biodegradable Zn-Mg alloy porous scaffolds by laser powder bed fusion (L-PBF). By using the pre-alloyed Zn-xMg (x = 1, 2 and 5 wt.%) powder and the optimized processing conditions, high fusion quality with the relative density greater than 99.5% was confirmed for the L-PBF parts. The influence of Mg content on microstructure, mechanical properties, in vitro corrosion, cytocompatibility, in vivo degradation, biocompatibility and osteogenic effect was investigated. Fine α-Zn grains and precipitation phases including Mg 2 Zn 11 and MgZn 2 were observed in the Zn-xMg L-PBF parts. The hardness increased, and the strength increases firstly and then decreased with increasing the Mg content. The compressive strength and elastic modulus of Zn-1Mg porous scaffolds reached the highest as 40.9 ± 0.4 MPa and 1.17 ± 0.11 GPa, respectively, equivalent to those of cancellous bone. The corrosion rate and cell viability slightly rose with increasing the Mg content. Histological analysis after 6-week and 12-week implantation in rabbit femurs showed enhanced bone formation around the Zn-1Mg porous scaffolds compared with pure Zn counterparts. In summary, Zn-1Mg porous scaffolds produced by L-PBF presented promising results to fulfill customized requirements of biodegradable bone implants. Additive manufacturing of biodegradable metal porous scaffolds is expected to solve the dual challenges from customized structures and bioactive function required for bone implants. It was the first to present a systematic in vitro and in vivo investigation into the compositions, microstructure, mechanical properties, biodegradation, biocompatibility and osteogenic effect of additively manufactured Zn-Mg alloy porous scaffolds. Reliable formation quality and performance evaluation was achieved by using the pre-alloyed Zn-xMg (x = 1, 2 and 5 wt.%) powder and the optimized laser powder bed fusion process. Although the Zn-1Mg scaffolds exhibited promising mechanical strength, biocompatibility, and osteogenic effect, their degradation rate needs to be further accelerated compared with the term of bone reconstruction. [Display omitted] [ABSTRACT FROM AUTHOR]

The study explores the impact of simulated inflammation on the corrosion behavior of pure Mo, a potential biodegradable metal for biomedical applications for the first time. Under simulated inflammatory conditions, Mo exhibits altered electrochemical properties, such as increased open circuit potential, higher corrosion rates, and reduced impedance as H 2 O 2 concentration rises. Immersion test confirm the higher corrosion rates with increases in H 2 O 2 concentration. Interestingly, pure Mo exhibit uniform corrosion behavior under aggressive simulated inflammation which is beneficial to maintain biomedical devices' mechanical integrity. Furthermore, the underlying biodegradation mechanism and the mechanism of inflammatory cell-released inflammation species induced corrosion were discussed. • The biodegradation behavior of pure Mo under simulated inflammatory conditions was evaluated for the first time. • Cell-released inflammation species H 2 O 2 affected the biodegradation behavior and increased the corrosion rate of pure Mo. • Pure Mo exhibits uniform corrosion behavior both in physiological environments and under simulated inflammatory conditions. • The biodegradation mechanism of pure Mo and the mechanism of inflammatory cell-released species induced corrosion were discussed. [ABSTRACT FROM AUTHOR]

In this study, the strain rate concentration is considered for high speed tensile test, which is now being recognized as a standard testing method. To evaluate the impact strength of engineering materials under high impact speed, Izod and Charpy tests are unsuitable since they cannot control the impact speeds and therefore do not coincide with the real failure of real products. For smooth specimens, the strain rate can be determined from the tensile speed u / t and specimen length l as ε ̇ smooth = u / tl . For notched specimens, however, the strain rate at the notch root ε ̇ notch should be analyzed accurately. In this study, therefore, the strain rate concentration factor defined as K t ε ̇ = ε ̇ notch / ε ̇ smooth is studied with varying the notch geometry and specimen length. It is found that the strain concentration factor K t ε ̇ can be estimated from stress concentration factor K t ∗ . [ABSTRACT FROM AUTHOR]

Highlights • The strain rate concentration is considered under both elastic and plastic-elastic analysis. • The strain rate concentration of flat specimen and round bar specimen is compared. • The influences of notch geometry including the notch angle and specimen length is studied. • The strain concentration factor can be estimated from stress concentration factor. • The fracture behavior can be predicted for the impact speed and temperature from the master curve. Abstract In this study, the impact strength of notched specimens of polymeric materials was studied by using high speed tensile test. Focusing on the strain rate at the notch root, the final fracture elongation was expressed in terms of the time-temperature superposition principle. Fracture behavior under various impact speed and temperature can be predicted by mean of the obtained master curves. The validity of the elastic strain rate concentration factor was confirmed through elastic-plastic analyses for both polycarbonate and polydimethylsiloxane copolymerized polycarbonate. It is found that the strain rate concentration factor can be estimated from the stress concentration factor for flat test specimens. [ABSTRACT FROM AUTHOR]