Enhancing the mechanical performance of DLP-printed HAp scaffolds: Impact of 72.5 wt% solid loading on achieving cortical-bone-level strength

This work establishes a new performance benchmark for DLP-printed hydroxyapatite (HAp) scaffolds by realizing a record-tier solid loading of 72.5 wt%, yielding an unprecedented compressive strength of ∼ 130.08 MPa and hardness of 3.59 GPa, surpassing all previously reported 3D-printed HAp materials. To overcome the rheological challenges of ultra-high ceramic loading, we developed a tailored slurry using 5 wt% BYK-180 and a black photoabsorber to achieve optimal flowability and precise light-scattering control. A strategic two-stage thermal protocol was engineered to ensure complete organic removal and near-theoretical densification (0.8% porosity) while preserving phase purity. The resulting scaffolds exhibit superior dimensional accuracy and structural integrity across complex architectures. Biological evaluations with MC3T3-E1 cells confirm robust cell adhesion, sustained proliferation, and enhanced osteogenic differentiation. By redefining the upper limits of both solid loading and structural integrity, this work provides a validated, scalable route for manufacturing high-performance, patient-specific bioceramic implants for advanced bone repair.