A temperature-insensitive silver nanostructures@graphene foam for high accuracy and full range human health monitoring

Recently, application-oriented strain sensor has been intensively investigated in the fields of human motion detection, personalized health management and portable medical diagnosis. Despite significant efforts in improving its sensitivity and linear sensing range, developing the wearable strain sensor with stable signal remains a challenge. Herein, we proposed an ideal hybrid material with nearly zero temperature coefficient resistance (TCR) for temperature-insensitive strain sensing: the silver nanostructures (AgNTs) were introduced to coat the graphene foam (GrF) conformably by hydrothermal growth. The nanoscaled metal additives (TCR > 0) not only endow GrF (TCR < 0) with high electrical stability (TCR ≈ − 0.3 × 10⁻³ °C⁻¹), but also offer the hybrid system additional structural elasticity, potential for next-generation of portable, stretchable and reliable devices. The resultant AgNTs@GrF hybrid material has been processed into a piezoresistive sensor with excellent sensing accuracy (strain error < 2.7%), satisfactory gauge factor (GF) of 227, wide sensing range up to 90% and good cyclic stability (> 3000 cycles). Moreover, our strain sensor can be easily mounted on human skin as an epidermal device for reliable detection of electrophysiological stimuli, thus showing a great promising in practical wearable applications.