Superstrong and supertough biomimetic nanocellulose composites with gradient bouligand architecture.

Lightweight structural materials with high strength and multifunctionality are urgently needed for advanced applications in aerospace, automotive, and sustainable engineering. However, conventional composites often suffer from limited mechanical performance, anisotropic mechanical behavior, or non-sustainable resource. Inspired by the Bouligand structure found in arthropod cuticles, we report a scalable approach for fabricating high-performance nanocellulose composites with a biomimetic gradient helical organization. By employing a programmable assembly process involving aligned cellulose nanofiber layers and an optimized interfacial matrix, we successfully constructed a dense, macroscopically isotropic bulk material. The multi-level hierarchical design promotes efficient energy dissipation through mechanisms such as microcrack deflection, interlayer sliding, and dynamic hydrogen bonding across scales. As a result, the composites exhibit outstanding mechanical performance, achieving a tensile strength of 649.9 MPa, fracture toughness of 192.1 MJ·m