Efficient dissociation of ultra-high-strength bamboo original fibers via deep eutectic solvent pretreatment for sustainable composite reinforcement.

Sustainable structural fibers are highly desirable because many conventional high-performance fibers are neither renewable nor biodegradable. Bamboo original fibers, which possess a natural hollow vascular bundle architecture, represent a promising biomass-derived reinforcement but are difficult to isolate without damaging their structure. Here, we develop a mild "top-down" strategy to efficiently dissociate intact bamboo original fibers (BpOFs) from pretreated natural bamboo using a deep eutectic solvent (ChCl/OA-DES) treatment at 110 °C for 1 h. The treatment selectively weakens parenchyma cell cohesion (elastic modulus reduced from 6.24 to 3.14 GPa) while preserving fiber cell stiffness (15.04 to 15.92 GPa), enabling rapid separation of vascular bundles through subsequent CH₃COOH/H₂O₂ delignification and simple roller compaction. Controlled hydrogen-bond reconstruction during drying enhances mechanical performance, yielding fibers with an apparent tensile strength of 1947 ± 217 MPa while retaining the native hollow structure. Analysis of the load-bearing cell wall further reveals an intrinsic cell-wall stress of 2636 ± 197 MPa, indicating highly efficient stress transfer within the cellulose framework. The preserved tubular architecture provides low density, flexibility, and favorable interfacial interactions with polymer matrices. When incorporated into epoxy resin, BpOFs enhance bending strength and impact resistance, demonstrating their potential as lightweight, renewable reinforcement for high-performance composites.