Biomimetic Organohydrogels with Tunable Architectures via Controlled Evaporation-Freeze/Thaw Self-Assembly.

Conventional hydrogels often face inherent limitations such as dehydration sensitivity, mechanical brittleness, and optical opacity, which severely restrict their advanced applications. In this study, we report a controlled evaporation-freeze/thaw self-assembly strategy for fabricating biomimetic poly(vinyl alcohol)/graphene oxide nanosheet (PG) organohydrogels with tunable architectures. Inspired by natural nacre, homogeneous layered PG organohydrogels are engineered to simultaneously achieve superior mechanical properties and optical transparency, enabled by a nacre-mimetic "brick-and-mortar" microstructure with aligned polymer-nanosheet interfaces. Remarkably, post-treatments combining prolonged evaporation and UV-induced reduction synergistically enhance the mechanical performance, yielding a tensile strength of 6.3 MPa and toughness of 43.0 MJ/m3, surpassing those of many reported poly(vinyl alcohol) (PVA)-based hydrogels. Furthermore, the humidity-regulated self-assembly process enables the creation of skin-like gradient PG organohydrogels, mimicking epidermal-dermal structural hierarchies to achieve optimized water retention and mechanical stability. This work establishes a universal platform for designing high-performance hydrogels that reconcile traditionally conflicting properties, offering great potential for applications in flexible electronics, soft robotics, and biointegrated devices that require environmental adaptability.