Basalt fibers with surface-coated hybrid carbon nanofillers for linear temperature and pressure sensing

Basalt fibers (BFs) are promising substrates for the fabrication of physical sensors owing to their excellent mechanical strength, thermal stability, and corrosion resistance. However, their inherent electrical insulation and inert surface chemistry severely hinder the development of high-performance fiber-based sensing devices. To address these limitations, we propose a synergistic surface modification strategy involving sequential KOH activation, fluorinated silane coupling agent (FAS-13) functionalization, and surface coating of a hybrid conductive layer of graphene oxide (GO) and carbon nanostructures (CNS). KOH etching increases basalt fiber surface roughness and exposes silanol (-Si-OH) groups to provide active sites for subsequent covalent grafting of FAS-13 to enhance interfacial adhesion. The GO/CNS hybrid leverages the functional groups of GO for improved dispersion of CNS and electrical conductivity to establish a robust three-dimensional conductive network. The resulting composite fiber (MFBFCG) exhibits outstanding electrical conductivity (∼230 S m^-1), a high temperature coefficient of resistance (TCR) of 0.18% per °C and excellent signal linearity (R² > 0.999) within 30-150 °C, as well as a rapid pressure response (response/recovery times of 78.0 ms and 62.8 ms). This work provides a novel and effective strategy to engineer multifunctional fiber sensors, showcasing their potential applications in smart textiles, aerospace thermal management, and industrial pressure monitoring systems.