Enhancing mechanical integrity of vat photopolymerization 3D printed hydroxyapatite scaffolds through overcoming peeling defects

In ceramic vat photopolymerization (VPP) fabrication, directly peeling originally designed scaffolds from the platform is efficient but often introduces defects, compromising the mechanical integrity of hydroxyapatite (HAp) scaffold. The peeling process involves the resistance of the HAp green scaffolds to peeling forces, which is influenced by its modulus and toughness. In this study, the peeling behavior of cubic-pore HAp (CP-HAp) green scaffolds with varying levels of modulus and toughness was investigated. The characterization results show that the HDDA CP-HAp scaffolds with relatively high levels of modulus and toughness could effectively resist the peeling forces and inhibit the occurrence of peeling defects. Stress concentration and inadequate toughness in the HEMA CP-HAp scaffolds lead to the formation of peeling defects. The CTFA and PHEA CP-HAp scaffolds with low modulus exhibit both peeling cracks and numerous pores. The cracks result from stress concentration, while the pores are caused by the coiled and loose molecular chain structure occupying space. Understanding the mechanism of peeling defect initiation in HAp porous scaffolds contributes to improving resistance to such defects and efficiently fabricating high-performance ceramic scaffolds using VPP.