Digital light processing of Al2O3–ZrO2 scaffolds: suspension optimization, microstructural control, and biocompatibility

Vat photopolymerization has emerged as a high-resolution and cost-effective approach for fabricating complex ceramic components with precise architectural control. In this study, Al 2 O 3 –5 vol.% ZrO 2 nanocomposite scaffolds were produced using a commercial low-cost digital light processing (DLP) system. A photosensitive suspension containing 30 vol.% solid loading was formulated and systematically optimized with respect to rheological behavior, cure depth, printing parameters, and thermal post-processing. The suspension exhibited shear-thinning behavior and low yield stress, ensuring adequate recoating and printing stability. Cure depth followed Beer–Lambert behavior, mainly governed by particle-induced scattering from refractive index mismatch between ceramic particles and resin. After optimized debinding and sintering at 1600 °C, the scaffolds reached a relative density of 87.9 ± 2.2% and linear shrinkage of 23.7 ± 0.7%, while preserving the designed lattice architecture without macroscopic defects. Micro-computed tomography revealed a total porosity of ∼66%, with 65.7% open and highly interconnected porosity, and pore sizes concentrated within the trabecular bone range. X-ray diffraction confirmed the predominance of tetragonal ZrO 2 , and SEM analysis showed homogeneous nanoparticle dispersion and refined microstructure. In vitro assays demonstrated absence of acute cytotoxicity and sustained osteoblast adhesion. These results highlight the potential of DLP-fabricated Al 2 O 3 –ZrO 2 nanocomposites for bone tissue engineering applications.