Expanding the mechanical and mass-transport combination for bone scaffolds: Through stretched structure

Optimizing the mechanical and mass-transport properties of porous biomaterials simultaneously can be challenging, as they often correspond one-to-one through structure. For instance, increasing permeability by reducing relative density frequently leads to lower mechanical properties. In this study, we introduced a stretched structure to optimize the two properties simultaneously. Initially, the stretched scaffolds were evaluated at the same porosity, revealing that the elastic modulus and permeability of the stretched scaffold are approximately twice that of the original type. Subsequently, the orientation dependence of these properties was investigated. The results suggest that the stiffness of the stretched structure in the width direction is compromised, aligning with the mechanical properties of cortical bone in shaft bones. The permeability of the stretched structure exhibits significant anisotropy, with values much higher than those of original structure. Moreover, our biological experiments demonstrate that extremely stretched structures exhibit low and uneven curvature, potentially impeding cell growth. Hence, striking a balance between curvature and the stretching method employed is crucial. The stretching method can also be applied to other strut-based structures, enabling greater design flexibility in achieving a desirable mechanical and mass-transport combination, providing a foundation for high-performance artificial bone prostheses.