Directly Converting Bulk Wood into Branch Micro-Nano Fibers to Synergistically Enhance the Strength and Toughness via Interface Engineering.

Hierarchical biobased micro/nanomaterials offer great potential as the next-generation building blocks for robust films or macroscopic fibers with high strength, while their capability in suppressing crack propagation when subject to damage is hindered by their limited length. Herein, we employed an approach to directly convert bulk wood into fibers with a high aspect ratio and nanosized branching structures. Particularly, the length of microfibers surpassed 1 mm with that of the nanosized branches reaching up to 300 μm. The presence of both interwoven micro- and nanofibers endowed the product with substantially improved tensile strength (393.99 MPa) and toughness (19.07 MJ m -3 ). The unique mechanical properties arose from mutual filling and the hierarchical deformation facilitated by branched nanofibers, which collectively contributed to effective energy dissipation. Hence, the nanotransformation strategy opens the door toward a facial, scalable method for building high-strength film or macroscopic fibers available in various advanced applications.