The influx and efflux of water in biological structures actuates reversible deformation and recovery processes that are crucial for mechanical functions in plants and animals. These processes utilize various mechanochemical mechanisms: swelling directed by the arrangement of cellulosic microfibrils in a bilayer construct, which generates different deformation patterns; lignification gradients; hierarchical foam-like inner structures, some of which also include swelling by hygroscopic cellulose inner cell layer; turgor pressure, which is activated by osmosis and acts at the cellular level, generating reversible motions. In this Review, we present representatives of each of these four mechanisms: pine cones, wheat awns, the twisted opening of Bauhinia pods and the seed of the stork’s bill; the resurrection plant; ice plant seed capsules and carrotwood seed pod; the wilting and redressing of plant stems. Natural polymeric materials produced by animals can also exhibit hydration-driven shape and strength recovery: bird feathers and hair are prime examples. Spider silk — a non-keratinous biopolymer — also exhibits humidity-driven reversible deformation. After describing these animal-based mechanisms, we outline bioinspired applications to actuate multifunctional and biocompatible smart materials, and indicate future directions of research with potential for new bioinspired designs.

水在生物结构中的涌入和流出促使可逆的变形和恢复过程，这对于动植物的机械功能至关重要。这些过程利用了多种机械化学机理：在双层构造中由纤维素微纤维的排列引导的溶胀，产生了不同的变形模式。木质化梯度; 分层的泡沫状内部结构，其中一些还包括由吸湿性纤维素内部细胞层引起的膨胀；膨胀压力，由渗透激活，作用于细胞水平，产生可逆运动。在这篇评论中，我们介绍了这四种机制的代表：松果，小麦芒，紫荆花的扭曲开口豆荚和鹳法案的种子；复活工厂；制冰种子胶囊和胡萝卜种子荚；植物茎的枯萎和补救。动物产生的天然聚合物材料也可以表现出水合作用的形状和强度恢复：鸟的羽毛和头发是主要的例子。蜘蛛丝（一种非角质生物聚合物）也表现出受湿度驱动的可逆形变。在描述了这些基于动物的机制之后，我们概述了生物启发的应用，以激活多功能和生物相容性智能材料，并指出了具有新的生物启发设计潜力的未来研究方向。