Microstructure and Mechanical Properties of Reticulated Titanium Scrolls

Titanium and its alloys find widespread use in skeletal implants and biomedical devices (e.g., stents and orthodontic applications) owing to their excellent corrosion resistance, bio-compatibility, static and fatigue strength, and lack of magnetism (an important property for magnetic imaging). Microporous titanium provides two additional advantages for implant applications: first, it reduces the stiffness of the material, thus reducing stress shielding, and, second, it improves implant anchorage by allowing bone ingrowth. To date, powder metallurgy approaches have been widely used to create porous Ti structures, through partial sintering, inclusion of pore formers, expansion of pores pressurized with argon or hydrogen gas, or replication of cellular polymers. Embrittlement often arises during processing due to the strong chemical affinity of titanium at elevated temperature with atmospheric oxygen, carbon, and nitrogen. Alternate efforts have focused on producing microarchitectured titanium, composed of lattice or truss structures with struts arranged periodically in space. These structures exhibit an outstanding combination of low density, high strength and stiffness, and good damage tolerance. To date, production methods for microarchitectured titanium have focused on replication precision casting, sintering of stacked wire arrays, as well as selective electron beam, or laser sintering of Ti powders. Recently, we introduced a new method for creating 3D microarchitectured Ti structures that combines: (i) direct ink writing (DIW) of planar lattices composed of two layers of orthogonally oriented, patterned TiH2 filament arrays, followed by (ii) rolling of these pliable lattices into scrolls, or folding into complex three-dimensional shapes, and finally (iii) heat-treating to reduce the hydride to metallic titanium. This newmethod is characterized by its simplicity, high shape versatility, and ability to control local geometry, as well as scalability to larger structures. Here, we use this novel C O M M U N IC A TI O N