The degradation behavior of magnesium-based orthopedic implants is strongly influenced by physiological induced mechanical loads, which can significantly impact their corrosion resistance and mechanical integrity. This study investigates the in vitro degradation of the magnesium alloy WE43MEO under high static tensile and compressive loading conditions, as well as the subsequent effects on cyclic mechanical performance. Samples with and without protective surface coatings (PEO and MgF) were immersed in phosphate-buffered saline (PBS) at 37°C for up to 10 days under static tensile or compressive loads of 230 N (≈50 MPa). To assess degradation behavior, pH evolution, hydrogen gas release, and mass loss were monitored. Following corrosion exposure, fatigue life was evaluated using cyclic loading (R = –1, 25 Hz, 656 N ≈136 MPa). Results revealed tendencies that uncoated samples under compressive load showed a 31% reduction in gas release after 72 hours, suggesting slower degradation, while tensile loading led to an 11% increase, indicating accelerated corrosion. Subsequent fatigue testing revealed tendencies that degradation under tensile loading reduced fatigue life by 35%, whereas compressive pre-loading extended it by 46.7% after 240 hours. Both PEO and MgF coatings reduced degradation impacts and improved fatigue resistance across all loading conditions. These findings underscore the crucial role of mechanical load direction and surface treatment in the design of biodegradable implants. Compressive loads appear beneficial for corrosion resistance and implant longevity, while tensile loads may compromise structural integrity. Protective coatings present an effective strategy to enhance performance under physiological conditions. These insights are essential for the development of more reliable and long-lasting biodegradable orthopedic devices.

In addition to the corrosion rate, corrosion morphology also plays a crucial role in the development of Mg alloys with the application of bioresorbable implants. This study investigates the influence of corrosion behaviour on the residual mechanical properties during corrosion of extruded Mg alloys for WE43, ZX10 and Mg10Gd. In particular, pitting corrosion is considered, as it can lead to premature failure. The project focuses on how critical pitting is exactly and whether the failure mechanism changes over the corrosion period to “small area failure”.

Fe-Mg alloys are promising for biomedical applications due to their absorbable nature and enhanced degradation rate with Mg addition. This study investigates the degradation behavior of Fe-Mg and Fe-Zn-Mg alloys in three simulated body fluids (PBS, HBSS, mHBSS). The alloys were produced by attrition milling and spark plasma sintering (SPS), which minimizes solute segregation and oxidation.Fe-Mg and Fe-Zn-Mg alloys were produced and characterized using SEM, XRD, and TEM. Degradation was evaluated in PBS, HBSS, and mHBSS over 3, 14, and 28 days at 37°C. pH evolution and ion release were monitored. Cytotoxicity assays were performed using MC3T3-E1 pre-osteoblasts and L929 fibroblasts. Zinc and magnesium were partially expelled from the iron matrix, forming periclase and zincite regions. Degradation products included oxides, oxyhydroxides, phosphates, and carbonates. Zinc modified Fe and Fe-Mg degradation behavior by enlarging Fe lattice parameter and increasing Mg solubility. Corrosion rates and degradation product formation were higher in HBSS, while HBSSm and PBS stabilized pH and reduced corrosion. Phosphate and carbonate layers influenced corrosion rates. HBSS released the highest amount of Mg ions. Cytotoxicity assays revealed significant toxicity, correlated with insoluble rust products in materials with higher corrosion rates.

Magnesium is one of the constituents of human body and it has many advantages as biomedical implant material. However, fast degradation of magnesium and excessive hydrogen evolution due to degradation may result in decrease of load-bearing capacity and tissue damage during a healing period. An addition of alloying element to magnesium is one of methods to control kinetics of degradation and hydrogen evolution. Among various alloying elements, Sn and Zn are known as the effective elements which can suppress hydrogen evolution and improve a protectiveness of surface film. They are also essential and non-toxic in human body. In this study, the in-vitro degradation behaviors of as-extruded Mg-5Sn-xZn alloys were evaluated systematically by electrochemical and immersion tests in Hank’s solution. The changes of microstructures and composition of surface film by addition of Zn strongly affected the corrosion behaviors of Mg-5Sn-xZn alloys. The increase of ZnO in the surface film was beneficial to corrosion resistance while higher fraction of Mg2Sn particles was detrimental to corrosion resistance with increasing Zn content. The size of Mg2Sn particle also affected the corrosion behaviors strongly.

The emerging field of 4D printing, which introduces time-dependent shape transformation into additively manufactured structures, offers unprecedented opportunities for dynamic biomedical applications. In this study, we explore the integration of biodegradable magnesium (Mg) and zinc (Zn) alloys—noted for their biocompatibility, mechanical properties, and controlled degradation profiles—into 4D-printed actuators designed for biomedical applications. Specifically, we focus on the application of these materials in addressing craniosynostosis, a congenital condition characterized by the premature fusion of cranial sutures, which impairs normal brain and skull growth. Traditional surgical interventions for craniosynostosis are invasive and often require repeated procedures. We propose a novel solution: 4D-printed, bioresorbable actuators composed of Mg/Zn alloys that can be implanted to apply gradual, controlled mechanical forces to promote cranial expansion over time, reducing the need for repeat surgeries. In this work, the selected smart 4D actuator designs for the shape-morphing structures were evaluated and how the degradation of the different biodegradable metallic elements control the rate and extent of expansion of the 4D actuators were studied in situ, as well as the temporal evolution of their load-bearing capability. Three different actuator designs are evaluated: a serpentine spring actuator, a conical spring actuator, and an auxetic spring actuator. They are made of two different metallic alloys: nitinol, for the shape-morphing part of the actuator, and the Mg based WE43MEO alloy, for the biodegradable anchoring elements that hold the spring in its initial state. The degradation of the anchoring elements triggers the shape morphing over a period of time in multiple steps depending on their configuration and corrosion rates. The initial result of the serpentine actuator is shown in Figure 1. A Zn alloy (Zn1Mg) will replace nitinol in the next step, to make the actuator fully biodegradable.

Mg-based alloys have been extensively studied for temporary implants due to their biodegradability, biocompatibility, mechanical properties, and biological functions of Mg+2 [1]. However, their main limitation is its high corrosion rate in physiological environment triggering an immune response. To reduce the degradation rate and improve biological response, an oxygen plasma-immersion ion implantation (O-PIII) treatment has been proposed [2]. Through O-PIII, a relatively homogeneous magnesium oxide is generated on the alloy surface. Moreover, Mg topography, wettability and electrochemical behavior were also modified, enhancing the interface between Mg based alloy- physiological environment.The final surface morphology after implantation was modified in terms of surface chemical composition (O amount, presence of Mg oxide and hydroxide-related species), the roughness, and the physical properties (such as surface energy), being influenced by the alloy features (grain boundaries, precipitates, second phases, surface texture, etc.). These results support the use of O-PIII technique and selected parameters as a potential surface modification, constituting a valid approach for clinical application. Biological tests related to cell viability (osteoblasts and neuronal cells) and hemocompatibility are carried out.

In this research, the possibility of 3D printing of ZX00, ZX50 and ZX50 with Ag addition was assessed from custom-made powder materials atomized via an induction method. As a result of the atomization process, powders with high sphericity were produced. The average particle size varied depending on the chemical composition of the alloys, measuring 201µm for ZX00, 107µm for ZX50, and 118µm for ZX50+Ag. The addition of Ag to ZX50 affected microstructural recrystallization, leading to the formation of the equiaxed grains, and this in turn, was a predominant factor affecting degradation parameters. The achieved proosity of the bulk materials was around 95%, which must be optimized in the future research. Nevertheless, modern powder production methods enable a broad research perspective on critically important biodegradable alloys for biomedical applications. The chemical composition of alloys can be tailored to impart desired properties, such as antibacterial activity. By mitigating porosity in additively manufactured magnesium alloys, their corrosion resistance can be significantly enhanced.