Oxygen-controlled bottom-up mask-projection stereolithography for ceramic 3D printing

To fabricate ceramic components with a complex structure, the bottom-up mask-projection stereolithography (MP-SL) technique is currently employed. However, a fracture or a defect is normally found because of the large separation force formed between the newly cured layer and the bottom surface of the slurry tank. Hence, to overcome this issue, an oxygen-permeable layer is integrated into the conventional MP-SL system for printing a β-TCP ceramic slurry in this study. The system is based on the fact that oxygen inhibits the photopolymerization process by consuming free radicals. The effects of the light exposure time and oxygen concentration on the curing depth and thickness of the oxygen-inhibition layer were investigated. Moreover, the separation forces were indirectly determined using a weight sensor. The results show that the oxygen-inhibition layer helped in reducing the separation force by 60% compared to that wherein oxygen is not employed. The solid loading could be increased by up to 44 vol% and the printable cross-sectional area by 5 times. In summary, the proposed oxygen-controlled bottom-up MP-SL technique helped in improving the ceramic printing efficiency and product quality.