A spiral brick-and-mortar nanocellulose fiber with high strength, fatigue resistance and enhanced fire safety.

Currently, the integration of functional materials with traditional fiber materials has demonstrated broad application prospects in critical fields such as sensors, energy devices, and biomedicine. However, the challenge of simultaneously achieving multifunctionality and excellent mechanical properties in fiber materials remains. Herein, we report nacre-inspired spiral "brick-and-mortar" composite fibers constructed from bacterial cellulose (BC) and montmorillonite (MMT) via an aerosol-assisted biosynthesis (AABS) and a bioinspired spiralization strategy. Benefiting from the 3D network of BC and the bioinspired spiral hierarchical architecture, the obtained composite fibers exhibit enhanced mechanical properties, including high tensile strength (558 ± 26 MPa), high toughness (24.9 ± 3.2 MJ m-3) and fatigue resistance (80 000 cycles of 180° bending). Additionally, the composite fibers achieve self-extinguishing properties, which are hard to obtain with traditional cellulose fibers. Hence, this bioinspired structural design effectively reconciles the trade-off between functionality and mechanical integrity, offering a generalizable pathway toward sustainable high-performance fibers.