Benchmarking of additive manufacturing technologies for commercially-pure-titanium bone-tissue-engineering scaffolds: processing-microstructure-property relationship

Abstract

This work provides the benchmarking of two additive manufacturing (AM) technologies suitable for the fabrication of commercially pure titanium scaffolds for bone tissue engineering, i.e., selective laser melting (SLM) and robocasting. SLM is a powder bed fusion technique that is industrially used for the AM of titanium parts, whereas robocasting is an extrusion technique mainly studied for the fabrication of ceramic scaffolds that requires post-sintering for the consolidation. A novelty of this work is to combine robocasting with pressure-less spark plasma sintering (PL-SPS) for the fabrication and fast consolidation of titanium scaffolds. The results show that the metallurgical phenomena occurring in both techniques are different. Melting and fast solidification in SLM produced martensitic-like microstructure of titanium with low microporosity (6 %). In contrast, solid-state sintering in robocasting resulted in the equiaxed grain microstructure of alpha titanium phase with 13 % of microporosity. The mechanical performance of the scaffolds was determined by the microporosity of the rods rather than microstructure. Consequently, robocasting resulted in lower compressive yield strength and effective elastic modulus than SLM, which were in the range of human trabecular bone. Finally, both AM technologies produced cytocompatible scaffolds that showed evidence of in vitro osteogenic activity.