Mechanical performance of additively manufactured pure silver antibacterial bone scaffolds

Implant infection is a serious complication resulting in pain, mortality, prolonged recovery, and antimicrobial resistance (AMR). Reducing the risk-of-infection associated with tissue implants require imminent attention, where pure silver (Ag) offers enormous potential. However, the printability, mechanical performance nor microbial resistance of additively manufactured (AM) pure Ag is unavailable in literature. This is critical as Ag is thought to play a vital role in the development of AM patient-specific infection resistant implants in the decade to come. The study therefore additively manufactured 99.9% pure-Ag through selective laser melting (SLM) and systematically investigates its mechanical performance. The validated SLM process parameters were then used to conceive two fully porous bone scaffold each at approximately 68 and 90% (wt.) porosity. While the study brings to attention the potential defects in SLM pure-Ag through X-ray nanotomography (X-ray nCT), the mechanical properties of porous Ag scaffolds were found to be similar to cancellous bone. The study achieved the highest SLM pure-Ag density of 97% with Young's modulus (E), elastic limit (σ_e), yield strength (σ_y), ultimate strength (σ_ult) and ultimate strain (ε_ult) in the range of 15.5-17.8 GPa, 50.7-57.7 MPa, 57.6-67.2 MPa, 82.4-95.9 MPa and 0.07-0.10 respectively. The antimicrobial efficacy of printed silver was tested against the common implant infection-causing Staphylococcus aureus and led to 90% and 99.9% kill in 4 and 14 h respectively. The study, therefore, is a first step towards achieving a new generation Ag-based AM infection resistant porous implants.