Hydrogels are widely used materials due to their biocompatibility, their ability to mimic the hydrated and porous extracellular microenvironment, as well as their ability to tune both mechanical and biochemical properties. However, most hydrogels lack mechanical toughness, and shaping them into complicated three-dimensional (3D) structures remains challenging. In the past decade, tough and stretchable double-network hydrogels (DN gels) were developed for tissue engineering, soft robotics, and applications that require a combination of high-energy dissipation and large deformations. Although DN gels were processed into simple shapes by using conventional casting and molding methods, new 3D printing methods have enabled the shaping of DN gels into structurally complex 3D geometries. This review will describe the state-of-art technologies for shaping tough and stretchable DN gels into custom geometries by using conventional molding and casting, extrusion, and optics-based 3D printing, as well as the key challenges and future outlook in this field.

中文翻译：

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双网络水凝胶的三维打印：最新进展、挑战和未来展望

水凝胶因其生物相容性、模拟水合和多孔细胞外微环境的能力以及调节机械和生化性能的能力而被广泛使用的材料。然而，大多数水凝胶缺乏机械韧性，将它们塑造成复杂的三维（3D）结构仍然具有挑战性。在过去的十年中，坚韧且可拉伸的双网络水凝胶（DN 凝胶）被开发用于组织工程、软机器人以及需要高能量耗散和大变形相结合的应用。尽管使用传统的铸造和成型方法将 DN 凝胶加工成简单的形状，但新的 3D 打印方法可以将 DN 凝胶塑造成结构复杂的 3D 几何形状。本综述将描述通过使用传统的成型和铸造、挤出和基于光学的 3D 打印将坚韧且可拉伸的 DN 凝胶塑造成定制几何形状的最先进技术，以及该领域的主要挑战和未来前景。