Dopamine-containing hydrogels were synthesized by copolymerization of dopamine methacrylamide (DMA), N,N-dimethylacrylamide (DMAA), and an N,N′-methylenebisacrylamide (BIS) crosslinker in a mixed solvent of water and DMSO. The association of DMA was formed by simply immersing in water to facilely reinforce the hydrogel due to the introduction of the second physical crosslinking. The tensile strength of the hydrogels was increased greatly and regulated in a wide range from 200 kPa to over 2 MPa. The association of DMA was destroyed upon immersing in DMSO. This reversible formation and dissociation of the association structure endowed the hydrogel with shape memory and actuating capabilities. Rapid shape fixing in water and complete shape recovery in DMSO was realized within several minutes. Bioinspired functional soft actuators were designed based on the reversible association and metal ion coordination of DMA, including fast responsive hydrogel tentacles, programable multiple shape change, reversible and versatile painting and writing “hydrogel paper”. The facile preparation and strength regulation provide a new way to design novel soft actuators through solvent exchange, and will inspire more complex applications upon combining the association with other properties of mussel inspired dopamine derivatives.

中文翻译：

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超强多巴胺水凝胶，具有形状记忆和受溶剂交换调节的生物启发性驱动行为†

通过将多巴胺甲基丙烯酰胺（DMA），N，N-二甲基丙烯酰胺（DMAA）和N，N在水和DMSO的混合溶剂中的'-亚甲基双丙烯酰胺（BIS）交联剂。DMA的缔合是由于引入了第二种物理交联作用而通过简单地浸入水中以轻松增强水凝胶而形成的。水凝胶的拉伸强度大大提高，并在200 kPa至2 MPa以上的宽范围内调节。浸泡在DMSO中会破坏DMA的关联。缔合结构的这种可逆形成和解离赋予水凝胶以形状记忆和致动能力。在几分钟内即可实现在水中的快速形状固定和在DMSO中的完全形状恢复。基于DMA的可逆结合和金属离子配比设计了具有生物灵感的功能性软执行器，其中包括快速响应的水凝胶触角，可编程的多种形状变化，可逆的多功能绘画和书写“水凝胶纸”。简便的制备和强度调节为通过溶剂交换设计新颖的软执行器提供了新的途径，并且结合了贻贝激发的多巴胺衍生物的其他性能，将激发更复杂的应用。