Fabrication of novel 316L stainless steel scaffolds by combining freeze-casting and 3D-printed gyroid templating techniques

Abstract

Porous metals have been widely investigated as bioimplants to repair cancellous bone defects. Nevertheless, how to endure extreme stress and strike a balance between load-bearing performance, elastic modulus, and permeability are important issues. Freeze-casting is a novel technique for manufacturing micro-scale open-cellular lamellar porous materials. However, the pore size is relatively small because of the inherent constraints of the ice template. On the other hand, the scaffold with gyroid pore structures has been proven to have higher permeability due to its larger and smoother channels. To combine the advantages of both porous structures, the present study aims to develop dual-scale 316L stainless steel (316L SS) porous structures by incorporating the 3D-printed gyroid templates into the freeze-casting to further improve the lightweight, specific strength, energy absorption, and permeability of the porous structures. The results showed that macro-scale gyroid channels were successfully built into the micro-scale open-cellular lamellar porous scaffolds. The porosity of dual-scale scaffolds was 70.1 %–74.4 %, which was higher than that of 53.1 %–66.5 % in the single-scale scaffolds. The elastic moduli of the single-scale scaffolds were higher than that of the dual-scale scaffolds; both were within the range of human cancellous bone, demonstrating their mechanical compatibility. Furthermore, the dual-scale scaffolds presented a prominent rise in permeability compared to the single-scale scaffolds. Notably, the permeability of the 3G series scaffolds was comparable to human cancellous bone. In summary, the hierarchical 316L SS scaffolds with controllable macro-scale gyroid channels exhibit great potential for biomedical applications.