Recently, hydrogel-based soft materials have demonstrated huge potential in soft robotics, flexible electronics as well as artificial skins. Although various methods are developed to prepare tough and strong hydrogels, it is still challenging to simultaneously enhance the strength and toughness of hydrogels, especially for protein-based hydrogels. Herein, a biomimetic “salting out—alignment—locking” tactic (SALT) is introduced for enhancing mechanical properties through the synergy of alignment and the salting out effect. As a typical example, tensile strength and modulus of initially brittle gelatin hydrogels increase 940 folds to 10.12 ± 0.50 MPa and 2830 folds to 34.26 ± 3.94 MPa, respectively, and the toughness increases up to 1785 folds to 14.28 ± 3.13 MJ m⁻³. The obtained strength and toughness hold records for the previously reported gelatin-based hydrogel and are close to the tendons. It is further elucidated that the salting out effect engenders hydrophobic domains, while prestretching facilitates chain alignment, both synergistically contributing to the outstanding mechanical properties. It is noteworthy that the SALT demonstrates remarkable versatility across different salt types and polymer systems, thus opening up new avenues for engineering strong, tough, and stiff hydrogels.

中文翻译：

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仿生“盐析-对齐-锁定”策略设计强韧的水凝胶

最近，基于水凝胶的软材料在软机器人、柔性电子产品以及人造皮肤方面表现出了巨大的潜力。尽管已经开发了多种方法来制备坚韧且坚固的水凝胶，但同时增强水凝胶的强度和韧性仍然具有挑战性，特别是对于蛋白质基水凝胶。在此，引入仿生“盐析-排列-锁定”策略（SALT），通过排列和盐析效应的协同作用来增强机械性能。作为一个典型的例子，初始脆性明胶水凝胶的拉伸强度和模量分别增加940倍至10.12±0.50 MPa和2830倍至34.26±3.94 MPa，韧性增加1785倍至14.28±3.13 MJ m ^-3。所获得的强度和韧性保持了之前报道的明胶基水凝胶的记录，并且接近肌腱。进一步阐明，盐析效应产生疏水域，而预拉伸促进链排列，两者协同促进优异的机械性能。值得注意的是，SALT 在不同的盐类型和聚合物系统中表现出卓越的多功能性，从而为工程坚固、坚韧和坚硬的水凝胶开辟了新途径。