Oxygen plays a critical role in the photopolymerization process resulting in the formation of solid structures from liquid resins during three-dimensional (3D) printing: it acts as a polymerization inhibitor. Upon exposure to light, oxygen is depleted. As a result, the polymerization process becomes activated. Electron paramagnetic resonance (EPR) imaging is described as a tool to visualize changes in oxygen distribution caused by light exposure. This nondestructive method uses radio waves and, therefore, is not constrained by optical opacity offering greater penetrating depth. Three proof-of-principle imaging experiments were demonstrated: (1) spatial propagation of the photopolymerization process; (2) oxygen depletion as a result of postcuring; and (3) oxygen visualization in a 3D printed spiral model. Commercial stereolithography (SLA) resin was used in these experiments. Lithium octa-n-butoxynaphthalocyanine (LiNc-BuO) probe was mixed with the resin to permit oxygen imaging. Li-naphthalocyanine probes are routinely used in various EPR applications because of their long-term stability and high functional sensitivity to oxygen. In this study, we demonstrate that EPR imaging has the potential to become a powerful visualization tool in the development of 3D printing technology, including bioprinting and tissue engineering.

中文翻译：

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用于立体光刻 3D 打印的光敏树脂中的快速扫描 EPR 氧气成像


氧气在三维 (3D) 打印过程中从液体树脂形成固体结构的光聚合过程中起着至关重要的作用：它充当聚合抑制剂。一旦暴露在光下，氧气就会耗尽。结果，聚合过程被激活。电子顺磁共振（EPR）成像被描述为一种可视化因曝光引起的氧气分布变化的工具。这种无损方法使用无线电波，因此不受光学不透明度的限制，提供更大的穿透深度。演示了三个原理验证成像实验：（1）光聚合过程的空间传播； (2)后固化造成的缺氧； (3) 3D 打印螺旋模型中的氧气可视化。这些实验中使用了商业立体光刻 (SLA) 树脂。将八正丁氧基萘酞菁锂 (LiNc-BuO) 探针与树脂混合以进行氧成像。由于其长期稳定性和对氧的高功能敏感性，锂萘酞菁探针通常用于各种 EPR 应用。在这项研究中，我们证明 EPR 成像有潜力成为 3D 打印技术（包括生物打印和组织工程）开发中强大的可视化工具。