Extrusion-based additive manufacturing of zinc bone scaffolds based on triply periodic minimal surfaces

Extrusion-based additive manufacturing is an emerging approach for fabricating architecturally complex biodegradable metallic bone implants, enabling zinc (Zn) to be processed into intricate scaffold architectures. Here, triply periodic minimal surface (TPMS) Zn scaffolds with gyroid, diamond, and I-WP architectures were fabricated by extrusion-based additive manufacturing followed by debinding and sintering. Scaffolds with solid fractions of 20, 30, and 40 vol% were produced, and the 30 vol% scaffolds were selected for characterization. All architectures retained TPMS geometries and exhibited interconnected pore networks with open porosities exceeding 55%, while the gyroid showed the highest shape fidelity. Degradation rates decreased from 0.070–0.087 mm/year at day 7 to 0.039–0.052 mm/year at day 28, with the diamond degrading slowest. Before immersion, the diamond exhibited the highest compressive strength (5.5 ± 0.4 MPa) and elastic modulus (0.67 ± 0.19 GPa). During immersion, compressive strength increased due to corrosion-product deposition. Finite element and computational fluid dynamics analyses revealed architecture-dependent mechanical and transport behavior, with the gyroid showing the highest permeability and lowest pressure drop. All scaffolds supported preosteoblast attachment, with the gyroid showing the highest metabolic activity. These findings demonstrate that TPMS architecture strongly governs the structural, degradation, mechanical, transport, and biological performance of extrusion-printed Zn scaffolds.