Characterization approach on the extrusion process of bioceramics for the 3D printing of bone tissue engineering scaffolds

Abstract

The present study proposes a characterization approach for the extrusion process of hydroxyapatite (HA) paste considering the nonlinear characteristics of bioceramics materials with the aim of printing high-resolution ceramic scaffolds using low-temperature extrusion 3D printing technology. A novel method named the three-point experimental extrapolation was executed to analyze the necessary extrusion pressure in relation to the extrusion velocity. This new approach presented a higher analytical accuracy as compared to previous methods. The optimum layout of the 3D printer was obtained by the comparative analysis of four typical topological constructions. On this basis, three main factors affecting the extrusion pressure of bioceramics materials, namely paste formulation (solvent content), nozzle length-to-diameter ratio, and the extrusion velocity, were selected as the control factors, and a series of experiments were performed using the L27 (313) orthogonal array. The results indicate that all the control factors significantly affected the extrusion pressure, of which the length-to-diameter ratio of nozzle exhibited the greatest effect. The scaffold printed using low-temperature extrusion 3D printing technology exhibited a uniform microstructure following the optimization of the printing parameters, which validated the ability of the process to accurately control the microstructure. The results of the study can be considered as a guide for the 3D printing of high-resolution bone tissue engineering scaffolds and can be employed to further compression mold bioactive polyetheretherketone/hydroxyapatite (PEEK/HA) composites.