Nature-inspired tooth-mimetic bamboo hierarchical composites with superhard, waterproof, and stain-resistant protective structures

Abstract Conventional bamboo waterproofing modifications frequently face limitations such as complex processing, limited functionality, inadequate mechanical durability, and reliance on petroleum-based polymers. Inspired by the hierarchical enamel-dentin structure of teeth, we propose a novel biomimetic strategy that utilizes bamboo’s intrinsic components to in situ generate a robust 170 µm-thick protective layer. This is achieved through selective surface delignification, directional NaIO 4 oxidation, and subsequent cell wall reconstruction via hot-pressing, effectively overcoming these longstanding challenges. Within this structure, the protective layer of the resulting tooth-mimetic bamboo hierarchical composite (TMB) forms via plasticization induced by the hydroxyl-aldehyde condensation reaction of dialdehyde cellulose, while the core layer densifies during hot-pressing. Consequently, TMB exhibits exceptional waterproofing, demonstrating a 99.0% reduction in surface water absorption rate compared to natural bamboo (NB). Remarkably, the protective layer maintains its waterproofing efficacy even after enduring over 100 cycles of abrasion and peeling. Additionally, TMB effectively repels common household liquids (e.g., coffee, milk, juice), and stubborn stains such as those from oil-based markers can be readily wiped off. Notably, TMB simultaneously achieves significant mechanical enhancement, attaining a Shore hardness of 92.0 HD alongside outstanding flexural and tensile properties. As a scalable composite material, TMB offers innovative strategies for protecting bamboo-based products and holds significant promise for diverse applications.