Decoupling optical and mechanical trade-offs in photonic hydrogels via bioinspired multi-network architecture

The mechanochromic photonic hydrogels based on cellulose nanocrystals (CNCs) face a contradiction between vividness of structural color and mechanical robustness. Inspired by octopus iridophores, a multi-network synergistic strategy was designed to overcome this challenge. A CNC/polyacrylamide/waterborne polyurethane (CPW) composite hydrogel was fabricated through co-assembly, precursor permeation, and thermal polymerization. This approach embedded a glucose-modified CNC (gCNC) chiral template within an interpenetrating elastic matrix, forming a triple network architecture. Dynamic hydrogen bonding endowed remarkable mechanical properties (420 kPa tensile strength, 821% elongation) while preserving structural order. Consequently, the hydrogel achieved reversible color switching from near-infrared to the full visible spectrum upon stretching, with a reflection peak varying from 467 to 670 nm. This work demonstrated its application in customizable information encryption, where encoded patterns are accurately revealed under specific strain with good cyclic durability. It not only provides a special biomimetic paradigm for designing intelligent responsive materials but also marks a key step toward the practical application of bio-based photonic materials in advanced and extreme environments.