Lattice Ti structures with low rigidity but compatible mechanical strength: Design of implant materials for trabecular bone

The development of porous metals to alleviate the effects of stress shielding in bone will help improve the function of metallic biomaterials in orthopaedic applications. A critical step in advancing this technology is to design metallic structures with low rigidity that is comparable with bone tissue, but with good mechanical strength. In this study, porous titanium (Ti) structures with periodic cell topologies were designed to achieve tunable mechanical properties. The versatility of the design scheme was demonstrated by examining lattice designs with different stiffness properties achieved by using the Selective Laser Melting (SLM) technology. The fabricated porous Ti exhibited a low modulus of 1.05 GPa but a high compressive strength of 55 MPa. Large deformation analysis using digital image correlation (DIC) technique indicated uniform strain patterns at micro-trusses, suggesting the overall high quality of the structure with absence of local flaws. A functionally-graded stiffness design was further investigated by varying the diameters of micro-trusses within the structure. A stiffness graded material may be favourable for anatomical site that has strong depth-dependent variations, such as in trabecular bone microstructures.