Microstructure and mechanical properties of 3D-printed zirconia bone scaffold: Experimental and computational analysis

Microextrusion-based additive manufacturing of zirconia-based bioceramics is capable of fabricating design-specific architectures with high mechanical strength properties and relative density. We developed a novel organic residue-free binder system for zirconia paste printing (ZP²) with the shear-thinning properties apropos to microextrusion-based 3D printing. Based on thermogravimetric analysis, debinding protocol was established followed by high-temperature heat treatment under four sintering conditions. Quantitative linear shrinkage (32.3%–42.7% ranging from in-plane to vertical direction), density (83.3%–87.5%), and surface roughness (7.7–13.8 µm from the parallel to the perpendicular to the infill direction) as a factor of sintering conditions (1400°C–1500°C for 3–4 h) were analyzed. Whereas qualitative phase assemblage demonstrated “sintering condition independent” phase stability; grain growth and reduction in porosity were observed in the microstructure with increment in sintering temperature and hold time. Interestingly, at higher temperature and hold time, the compressive (46–72.4 MPa) and tensile strength (16.2–23.1 MPa) properties experienced a trade-off between grain growth and reduction in porosity. The ZP² scaffolds sintered at lower temperature and hold time qualified for the bone scaffold applications having interconnected porosities, biologically relevant surface roughness, and human bone mimicking mechanical properties. With a unique finite element analysis recipe, the mechanical behavior of the “life-like” reconstructed computer aided design (CAD) geometries identical to real 3D-printed-sintered ZP² scaffolds was quantitatively predicted.