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 (CaTiSiO5) 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.