Additive manufacturing of zinc auxetic stents: tuning mechanical properties through process and structural design

Additive manufacturing (AM) of bioresorbable metals is gaining momentum, with material selection, design, and manufacturing processes crucially impacting performance. Zinc (Zn) is a promising bioresorbable metal, but the challenges in its processability via the AM, and its low mechanical performance have limited its potential applicability. This study investigates a novel approach to laser powder bed fusion (LPBF) AM processing of Zn stents by combining the effects of varying process parameters and structural topology design. A precise set of process parameters was developed to overcome the limitations of LPBF for Zn, achieving high-density parts while diversifying microstructural properties across builds. In devising the structural topology of the stents, auxetic structures were implemented to advance the mechanical performance of the stents via design. The interrelationship between microstructural properties (process) and topology (design) was evaluated through mechanical testing of 12 printed Zn stents, each exhibiting unique properties with yield stresses ranging from 0.06 to 3.24 MPa and ultimate stresses from 0.09 to 4.22 MPa. To further assess the influence of process parameters, feature size, and print orientation, miniaturized tensile test specimens were designed, printed, and tested. The mechanical properties obtained from these tests served as a reference for FEM analysis, enabling more accurate predictions of the stents' mechanical behavior. The proposed method and the diverse mechanical performance observed in this study suggest a promising pathway for fabricating patient-specific bioresorbable Zn stents.