Creating Unidirectionally Macrochanneled Zirconia Bone Scaffolds with Elongated Microporous Frameworks via Vat Photopolymerization Using Phase-Separable, Photocurable Vehicle

Abstract

Unidirectionally macrochanneled tetragonal zirconia polycrystals (TZP) scaffolds, comprising elongated microporous frameworks, were fabricated via vat photopolymerization (VP) using a solution of 75 wt% camphene and 25 wt% 1,6-hexanediol diacrylate (HDDA) as a phase-separable, photopolymerizable vehicle. The camphene/HDDA solution underwent phase separation at 5 °C, accompanied by the recrystallization and dendritic growth of camphene, thereby generating three-dimensionally interconnected camphene crystal networks enclosed by HDDA. Following the photopolymerization of HDDA, the scaffolds were freeze-dried to remove the camphene crystals and subsequently heat-treated for debinding to eliminate organic phases, including photopolymerized HDDA, the dispersant, and the photoinitiator. The effect of sintering temperature on the geometry of the micropores and the densification of the TZP walls was examined. The optimum sintering condition (1500 °C for 3 h) enabled the creation of elongated micropores with a volume fraction of 61.17 ± 0.90 vol%, surrounded by highly densified TZP walls. The fabricated scaffolds exhibited well-defined macrochannels arranged in a hexagonal pattern, separated by microporous frameworks. Their overall porosity was as high as 74.65 ± 0.73 vol%, owing to the high framework microporosity. Despite their high porosity, the scaffolds achieved a compressive strength of 53.10 ± 8.19 MPa and a compressive modulus of 364.38 ± 70.90 MPa.