Ultra-strong bamboo macrofibers via selective delignification and microwave drying for lightweight structural composites

Natural fibers offer a sustainable alternative to synthetic reinforcements, but their mechanical properties often lag behind those of synthetic fibers. Herein, we report a novel strategy combining selective delignification and microwave-assisted drying to fabricate ultra-strong bamboo macrofibers for lightweight structural composites. Selective delignification removes lignin from bamboo while retaining the cellulose framework. Subsequent rapid microwave drying induced a dense alignment of the cellulose protofibrils, which not only shortened the drying time (24 h to 1 h) but also greatly increased the fiber strength. The resulting bamboo crude fibers exhibit excellent mechanical properties (tensile strength of 1148 ± 52 MPa. Due to their low density, these fibers have a very high specific strength (7.2092 × 10 6 N·m·kg −1 ), even exceeding some carbon and glass fibers, making them ideal for lightweight structures. When used to reinforce polymer composites, bamboo can significantly improve the mechanical properties of the material while adding minimal weight. The MD-fiber@PVA composites exhibited a 267 % increase in ultimate stress, rising from 27.32 MPa (neat PVA) to 100.32 MPa, whereas the AD-fiber@PVA composites achieved a 193 % improvement. Due to the lower density of the large fibers, the specific strength reaches 0.110 × 10⁶ N m kg-1 for MD-fiber@PVA and 0.087 × 10⁶ N m kg-1 for AD-fiber@PVA. Moreover, the use of fast-growing bamboo and energy-efficient microwave processing underscores the environmental and economic viability of this bio-based fabrication approach. It offers a green manufacturing route for high-performance fiber materials and aligns with sustainability goals by reducing reliance on petrochemical fibers and lowering carbon footprints. Ultra-strong bamboo fibers and PVA composites prepared from natural bamboo. • Ultra-strong bamboo macrofibers produced via selective delignification. • Microwave drying enables rapid fiber processing within a short period of time. • Bamboo macrofibers exhibit tensile strength comparable to synthetic fibers. • Composites of bamboo fibers are equipped with high strength and low weight. • Bamboo macrofiber composites are biophilic, sustainable and cost-effective high-performance reinforcing materials.