Novel strategy for mechanically tunable and bioactive metal implants.

Metals have been used as biostructural materials because of outstanding mechanical reliability. However, low bioactivity and high stiffness in biological environments have been major issues of metals, causing stress shielding effects or foreign body reactions after implantation. Therefore, in this study, densified porous titanium has been introduced to achieve comparable mechanical properties to hard tissues and bioactivity that promote a better interface between the implant and bone. Porous titanium scaffolds were successfully fabricated through dynamic freezing casting, and were densified, controlling the degree of densification by applied strain. During densification, structural integrity of porous titanium was well maintained without any mechanical deterioration, exhibiting good pore connectivity and large surface area. Densified porous titanium possesses two important features that have not been achieved by either dense titanium or porous titanium: 1) mechanical tunability of porous scaffolds through densification that allows scaffolds to be applied ranging from highly porous fillers to dense load-bearing implants and 2) improved bioactivity through bioactive coating that is capable of sustainable release through utilizing high surface area and pore connectivity with controllable tortuosity. This simple, but effective post-fabrication process of porous scaffolds has great potential to resolve unmet needs of biometals for biomedical applications.