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-3, and puncture resistance of 178.4 N/mm—values that substantially exceed those of leading natural and synthetic structural counterparts. Moreover, the material demonstrates multifunctional characteristics, including tunable structural coloration, effective electromagnetic interference shielding, and exceptional stability across extreme temperatures. This work establishes a versatile and sustainable platform for the development of advanced structural materials suited for demanding environments such as spacecraft shielding, robotic systems, and next-generation vehicular technologies. Current nanocellulose bulk composites often struggle with pronounced anisotropy and limited structural control. Here, the authors report a programmable stacking and densification strategy for polymer reinforced delignified wood sheets to construct a gradient Bouligand architecture, forming lightweight composites with high isotropic mechanical properties.