Design and high-precision heated vat photopolymerization fabrication of bio-inspired gradient porous zirconia toughened alumina ceramics

Zirconia-toughened alumina (ZTA) ceramics exhibit outstanding potential for load-bearing orthopedic implants like intervertebral fusion cages, owing to their excellent mechanical properties and biocompatibility. However, the high elastic modulus and inherent brittleness of ZTA ceramics pose manufacturing challenges that limit clinical applications. Biomimetic structural design combined with vat photopolymerization 3D printing offers a promising solution for developing personalized ZTA fusion cages. Nevertheless, ultraviolet (UV) light scattering from the ceramic. Particles reduce printing resolution, leading to significant variations in the designed mechanical performance. In this study, bio-inspired porous ZTA ceramic fusion cages were developed, featuring a solid outer shell (0.25–0.5 mm thickness) with 50% core average porosity and 20%–60% porosity gradient. Mechanical simulations reveal that their mechanical compatibility with human autogenous bone tissue originates from the porosity gradient architecture and enlarged load-bearing zone, which optimizes stress distribution to enhance bearing capacity. For high-precision additive manufacturing of ZTA ceramic green bodies, a heated vat photopolymerization (H-VPP) technique was developed. By elevating the forming temperature, the exposure energy density required to achieve the same cured depth is reduced, which minimizes horizontal UV light scattering. The sintered ZTA ceramic fusion cages successfully replicate human autogenous bone tissue characteristics, exhibiting compressive strength of 32–198 MPa and elastic modulus of 2.4–6.6 GPa.