Conductive Ink Based on GNSs/MWCNTs for Fabricating Wearable Wash-Resistant Electrothermal Devices

Flexible wearable devices, which combine lightness, comfort, and intelligence, are developing rapidly in the fields of health monitoring, human–computer interaction, energy, and biomedicine. There is also a growing demand for a low-cost, washable, and flexible wearable device to meet the requirements of resource conservation and sustainability. In this study, graphene nanosheets (GNSs)/multiwalled carbon nanotubes (MWCNTs) washable conductive ink was prepared by liquid-phase exfoliation using graphite, MWCNTs, silane coupling agents, and high-adhesion resin. Its square resistance (Rsq) is only 26 Ω/sq (25 μm), and it can keep the resistance change within 10% after 5 simulated machine washes (1 h per wash). In addition, the printed electrothermal fabric (4 × 4 cm) can reach 54 °C at a low voltage of 5 V and consumes only 1.25 W. After 5 washes, the saturation temperature can still reach 50 °C, enabling insulation on the surface of the body and helping to create a smarter and more convenient personal thermal management system.