Laser Powder Bed Fusion-built Ti6Al4V Bone Scaffolds Composed of Sheet and Strut-based Porous Structures: Morphology, Mechanical Properties, and Biocompatibility

Abstract

Laser powder bed fusion (L-PBF)-built triply periodic minimal surface (TPMS) structures are designed by implicit functions and are endowed with superior characteristics, such as adjustable mechanical properties and light-weight features for bone repairing; thus, they are considered as potential candidates for bone scaffolds. Unfortunately, previous studies have mainly focused on different TPMS structures. The fundamental understanding of the differences between strut and sheet-based structures remains exclusive, where both were designed by one formula. This consequently hinders their practical applications. Herein, we compared the morphology, mechanical properties, and biocompatibility of sheet and strut-based structures. In particular, the different properties and in vivo bone repair effects of the two structures are uncovered. First, the morphology characteristics demonstrate that the manufacturing errors of sheet-based structures with diverse porosities are comparable, and semi-melting powders as well as the ball phenomenon are observed; in comparison, strut-based samples exhibit cracks and thickness shrinking. Second, the mechanical properties indicate that the sheet-based structures have a greater elastic modulus, energy absorption, and better repeatability compared to strut-based structures. Furthermore, layer-by-layer fracturing and diagonal shear failure modes are observed in strut-based and sheet-based structures, respectively. The in vivo experiment demonstrates enhanced bone tissues in the strut-based scaffold. This study significantly enriches our understanding of TPMS structures and provides significant insights in the design of bone scaffolds under various bone damaging conditions.