Prototypes for Bone Implant Scaffolds Designed via Topology Optimization and Manufactured by Solid Freeform Fabrication

The linking of computational design with precision solid freeform fabrication has tremendous potential for producing tissue scaffolds with tailored properties. We consider a new approach to optimizing the architecture of scaffolds based on jointly maximizing scaffold stiffness and diffusive transport in the interconnected pores. The stiffness of the scaffolds is matched to that of bone by choosing a suitable scaffold porosity. Moreover, the templates can be scaled to achieve target pore sizes whilst preserving their elastic and diffusive properties. The resultant structures have two major design benefits. First, the scaffolds do not have directions of low stiffness. In contrast, the Young's modulus of conventional layered-grid designs can be 86% less under diagonally-aligned loads than under axis-aligned loads. Second, the mass of the scaffold is used efficiently throughout the structure rather than being clumped in non load-bearing regions. We fabricate prototypes of the implants using selective laser melting and test their elastic properties. Excellent agreement between theory and experiment provides important confirmation of the viability of this route to scaffold design and fabrication.