Four-dimensional (4D) printing, combining three-dimensional (3D) printing with time-dependent stimuli-responsive shape transformation, eliminates the limitations of the conventional 3D printing technique for the fabrication of complex hollow constructs. However, existing 4D printing techniques have limitations in terms of the shapes that can be created using a single shape-changing object. In this paper, we report an advanced 4D fabrication approach for vascular junctions, particularly T-junctions, using the 4D printing technique based on coordinated sequential folding of two or more specially designed shape-changing elements. In our approach, the T-junction is split into two components, and each component is 4D printed using different synthesized shape memory polyurethanes and their nanohybrids, which have been synthesized with varying hard segment contents and by incorporating different weight percentages of photo-responsive copper sulfide-polyvinyl pyrrolidone nanoparticles. The formation of a T-junction is demonstrated by assigning different shape memory behaviors to each component of the T-junction. A cell culture study with human umbilical vein endothelial cells reveals that the cells proliferate over time, and almost 90% of cells remain viable on day 7. Finally, the formation of the T-junction in the presence of near-infrared light has been demonstrated after seeding the endothelial cells on the programmed flat surface of the two components and fluorescence microscopy at day 3 and 7 reveals that the cells adhered well and continue to proliferate over time. Hence, the proposed alternative approach has huge potential and can be used to fabricate vascular junctions in the future.

中文翻译：

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基于模块化光折纸的血管连接元件 4D 制造

四维 (4D) 打印将三维 (3D) 打印与时间依赖性刺激响应形状变换相结合，消除了传统 3D 打印技术在制造复杂空心结构方面的局限性。然而，现有的 4D 打印技术在使用单个可变形物体创建的形状方面存在局限性。在本文中，我们报告了一种用于血管连接处（特别是 T 形连接处）的先进 4D 制造方法，该方法使用基于两个或多个专门设计的形状变化元件的协调顺序折叠的 4D 打印技术。在我们的方法中，T 形接头分为两个组件，每个组件均使用不同合成的形状记忆聚氨酯及其纳米杂化物进行 4D 打印，这些材料是用不同的硬链段含量并通过掺入不同重量百分比的光响应铜来合成的硫化物-聚乙烯吡咯烷酮纳米颗粒。通过为 T 形接头的每个组件分配不同的形状记忆行为来演示 T 形接头的形成。对人脐静脉内皮细胞进行的细胞培养研究表明，细胞会随着时间的推移而增殖，并且几乎 90% 的细胞在第 7 天仍保持活力。最后，在近红外光存在下 T 形连接的形成已被证明将内皮细胞接种到两个组件的编程平坦表面上后，第 3 天和第 7 天的荧光显微镜显示细胞粘附良好并随着时间的推移继续增殖。因此，所提出的替代方法具有巨大的潜力，可用于未来制造血管连接。