Co-extrusion of highly loaded feedstocks for fabrication of stainless steel-bioceramic core-shell structures

Co-extrusion of multi-materials structures shows technological challenges and opportunities. Filaments made of a metallic core and a ceramic shell are one example of how structural and functional features can be combined in a single component to provide a synergic effect. In this work, we focused on the fabrication of shell and core-shell scaffolds for potential applications as bone substitutes. Stainless steel 316L was selected for the core material, whilst in situ synthesized sphene (CaTiSiO 5 ) bioactive ceramic was selected as a shell. The combination of a ductile core and a bioactive ceramic, so as scaffolds made of empty struts may represent a new generation of bone substitutes with mechanical properties closer to the ones of natural bone so as with improved bioactivity. Therefore, formulated inks were co-extruded in one step using a customized printing set-up. Microstructural and mechanical properties were investigated on shell and core-shell filaments and 3D structures. Shell bioceramics scaffolds possessed high porosity and target compression strength values. The sintering environment at the core-shell interface caused severe 316L oxidation thus compromising the ductility of the metallic part, however compression strength increased of 53% compared to shell structures. • A single-step co-extrusion set-up was customized to 3D print shell and core-shells structures • CaTiSiO 5 precursors as shell and 316L ink as core were used to produce bioceramics scaffolds with an empty or metallic core. • Reactive sintering was applied to synthesize CaTiSiO 5 in-situ • Both shell CaTiSiO 5 scaffolds and 316L-CaTiSiO 5 core-shell scaffolds exhibited mechanical properties compatible with scaffolds for bone replacement.