Production and evaluation of porous titanium scaffolds with 3-dimensional periodic macrochannels coated with microporous TiO ₂ layer

This study examined the utility of a combination of the thermoplastic green machining (TGM) and micro-arc oxidation (MAO) for the production of porous Ti scaffolds with 3-dimensional (3-D) periodic macrochannels coated with a microporous TiO ₂ layer, which would provide high mechanical properties and excellent biocompatibility simultaneously. The TGM technique allowed for the creation of tightly controlled 3-D periodic macrochannels with a diameter of ∼828-837 μm by machining a thermoplastic compound consisting of 70 vol% titanium hydride (TiH ₂) powder and 30 vol% thermoplastic binders, followed by heat-treatment in a vacuum. The overall porosity and mechanical properties of the porous Ti scaffolds were controlled by creating various periodic arrays of 6 × 6, 7 × 7, or 8 × 8 macrochannels in each face of a cube. The compressive strength and modulus was decreased from 358 ± 7 to 100 ± 8 MPa and from 5.2 ± 0.66 to 3.5 ± 0.32 GPa, respectively, with increasing porosity from 48 vol% to 64 vol%. The biocompatibility and bioactivity, which was assessed by in vitro cellular assays, were improved remarkably by creating a microporous TiO ₂ coating layer using the MAO treatment.