Strain-Stiffening Transparent Hydrogel: Integrating Mechanical Adaptability and Solar Polarization Positioning

Certain biological tissues exhibit the remarkable ability to rapidly stiffen in response to deformation, serving as a defense mechanism while concurrently polarizing incident light for navigation purposes. However, seamlessly integrating these distinct mechanical and optical properties into a single wet and soft synthetic material has proven challenging. In this study, we introduce a novel methodology to engineer a series of transparent anisotropic hydrogels. This approach involves low-humidity evaporation solvent gelation followed by structural reconstruction through sequential prestretching, cross-linking, and releasing steps. The resulting hydrogels boast high optical clarity, notable birefringence, and a significant strain-stiffening capacity of 10.4 at small strain intervals. Moreover, we enhanced the biomimetic capabilities of these hydrogels by incorporating dichroic molecules through a meticulous dyeing process. This integration allows us to demonstrate a biomimetic application, specifically in the context of solar polarization positioning. This research represents a substantial advancement in the development of synthetic materials that emulate the sophisticated mechanical and optical features observed in natural biological tissues.