Multifunctional MXene/CNTs Composite Fibers with High Strength, Conductivity, and Bending Sensitivity Fabricated via Sodium Alginate-Assisted Wet Spinning

Multicomponent nanocomposite fibers with synergistic properties are highly desirable for next-generation flexible electronics and sensors. In this study, MXene, carbon nanotubes (CNTs), and their composite fibers were successfully fabricated via a wet-spinning method using sodium alginate (SA) as a binder and fiber-forming agent. The morphology, mechanical properties, electrical conductivity, electrothermal behavior, and bending sensing performance of the resulting fibers were systematically investigated. All fibers exhibited longitudinal surface wrinkles and a nearly circular cross-section, indicating good process controllability. The MXene/CNTs@SA fibers, featuring a hierarchical synergistic network constructed from one-dimensional CNTs and two-dimensional MXene nanosheets, demonstrated significantly enhanced mechanical performance, with a tensile strength of 76.38 ± 7.09 MPa and conductivity of 16.14 ± 0.36 S·cm−1. Under a 12 V applied voltage, the MXene/CNTs@SA fibers achieved a saturation temperature of 52.77 °C and a power density of 2.95 kW·cm−3, demonstrating balanced electrothermal performance. Furthermore, the MXene/CNTs@SA fibers exhibited excellent flexibility and sensing stability, with resistance variations within ± 1.6% over repeated 100 bending–release cycles. The bending gauge factor was determined to be 7.36, confirming high sensitivity and cyclic durability. These results demonstrate that the wet-spun MXene/CNTs@SA composite fibers, with their robust mechanical strength, enhanced electrical conductivity, reliable electrothermal response, and superior bending sensitivity, hold great promise for applications in flexible electronic devices and wearable sensors.