Rapid Fabrication of Graphene Fibers and Fiber-Based Thermistors for Wearable Devices

Wet spinning of graphene oxide liquid crystals (GO LCs) is a scalable method for creating graphene fibers with applications in flexible and wearable devices. In this study, high-shear mixing using a rotational Couette flow with a small gap between the stator and rotor was used to efficiently produce LC phases from a dispersion of nanometer-thick monolayer GO flakes. One minute of high-shear mixing resulted in LC phases with higher viscosity than those produced by conventional magnetic stirring. Graphene fibers were obtained by wet spinning and subsequent chemical reduction of the GO LCs, achieving improved mechanical and electrical properties. Owing to the efficient production of GO LCs and subsequent graphene fibers, the graphene fibers were directly used as thermistors for flexible and wearable temperature sensors. The fiber thermistor exhibited a high temperature coefficient of resistance of −0.21 ± 0.01 %/°C, high linearity with a correlation coefficient of 0.999, a low time constant of 0.33 ± 0.07 s, and high repeatability. Therefore, this study demonstrated the potential of high-shear mixing for the rapid manufacturing of graphene fibers for wearable devices including smart textiles, soft robotics, and flexible healthcare devices.