Influence of surface condition on the degradation behaviour and biocompatibility of additively manufactured WE43.

The further development of future Magnesium based biodegradable implants must consider not only the freedom of design, but also comprise implant volume reduction, as both aspects are crucial for the development of higher functionalised implants, such as plate systems or scaffold grafts in bone replacement therapy. As conventional manufacturing methods such as turning and milling are often accompanied by limitations concerning implant design and functionality, the process of laser powder bed fusion (LPBF) specifically for Magnesium alloys was recently introduced. In addition, the control of the degradation rate remains a key aspect regarding biodegradable implants. Recent studies focusing on the degradation behaviour of additively manufactured Magnesium scaffolds disclosed additional intricacies when compared to conventionally manufactured Magnesium parts, as a notably larger surface area was exposed to the immersion medium and scaffold struts degraded non-uniformly. Moreover, chemical etching as post processing technique is applied to remove sintered powder particles from the surface, altering surface chemistry. In this study, cylindrical Magnesium specimens were manufactured by LPBF and surfaces were consecutively modified by phosphoric etching and machining. Degradation behaviour and biocompatibility were then investigated, revealing that etched samples exhibited the overall lowest degradation rates, but experienced large pit formation, while the reduction of surface roughness resulted in a delay of degradation.