Friction spun spandex/rGO/Ag/polyester core-sheath yarn with antibacterial activity for wearable sensors

Wearable sensors, which feature textile substrates integrated with conductive layers, have received increasing attention from researchers due to their huge potential in health management. However, the inevitable damage of conductive layer caused by friction and bacterial growth on the textile substrate during its direct contact with bare skin are still the issues that hinder the long-term service of wearable sensors. Herein, a core-sheath yarn was prepared by wrapping polyester (PET) fibers coated with reduced graphene oxide (rGO)/silver nanoparticles (Ag NPs) around the spandex filaments via friction spinning. The core-sheath structure guarantees good prevention of the interface composed of rGO and Ag NPs in between from friction, while the introduction of Ag NPs ensures antibacterial activity of the yarn. The morphology and chemical composition of the nanomaterials deposited on the surface of PET fibers was investigated to reveal the sensing mechanism of the yarn. Meanwhile, its sensing performance was comprehensively evaluated from the perspectives of sensitivity, durability and comparison of commercial ECG. Despite the fact that inevitable damage of the rGO/Ag layer occurred during the friction spinning process, the core-sheath yarn still featured a gauge factor of 8.11 and a threshold of sensing range up to 68.57 %. Apart from being able to detect respiratory signals, cardio signals with the frequency of 70 beat per min (bpm) was also recorded. Compared to signals with the frequency of 73 bpm recorded by a commercial ECG sensor simultaneously, the core-sheath yarn exhibited satisfying precision. Moreover, the existence of Ag NPs in the conductive interface endowed the yarn with ability to yield 13-mm and 15-mm wide growth inhibition zones of E. coli and S. aureus, respectively. The cardiorespiratory sensing ability coupled with antibacterial activity of the yarn suggested its satisfying sensitivity and prolonged service time, making it a promising wearable sensor subjected to direct skin contact for long-time cardiorespiratory monitoring.