Development of hybrid 3D printing approach for fabrication of high-strength hydroxyapatite bioscaffold using FDM and DLP techniques

This study develops a hybrid 3D printing approach that combines fused deposition modeling (FDM) and digital light processing (DLP) techniques for fabricating bioscaffolds, enabling rapid mass production. The FDM technique fabricates outer molds, while DLP prints struts for creating penetrating channels. By combining these components, hydroxyapatite (HA) bioscaffolds with different channel sizes (600, 800, and 1000 mu m) and designed porosities (10%, 12.5%, and 15%) are fabricated using the slurry casting method with centrifugal vacuum defoaming for significant densification. This innovative method produces high-strength bioscaffolds with an overall porosity of 32%-37%, featuring tightly bound HA grains and a layered surface structure, resulting in remarkable cell viability and adhesion, along with minimal degradation rates and superior calcium phosphate deposition. The HA scaffolds show hardness ranging from 1.43 to 1.87 GPa, with increasing compressive strength as the designed porosity and channel size decrease. Compared to human cancellous bone at a similar porosity range of 30%-40%, exhibiting compressive strengths of 13-70 MPa and moduli of 0.8-8 GPa, the HA scaffolds demonstrate robust strengths ranging from 40 to 73 MPa, paired with lower moduli of 0.7-1.23 GPa. These attributes make them well-suited for cancellous bone repair, effectively mitigating issues like stress shielding and bone atrophy.