Environment-friendly carbon nanotube based flexible electronics for noninvasive and wearable healthcare

Flexible and stretchable electronics have a wide variety of wearable applications in portable sensors, flexible electrodes/heaters, flexible circuits and stretchable displays. Spinnable carbon nanotubes (CNTs) constructed on flexible substrates are potential materials for wearable sensing applications owing to their high thermal and electrical conductivity, low mass density and excellent mechanical properties. Here, we demonstrate a wearable thermal flow sensor for healthcare using lightweight, high strength, flexible CNT yarns as hotwires, pencil graphite as electrodes, and lightweight, recyclable and biodegradable paper as flexible substrates, without using any toxic chemicals. The CNT-based sensor which could be utilized to monitor respiratory diseases is comfortably affixed to human skin and detects real-time human respiration. We also successfully demonstrate the temperature detecting functionality integrated in the same sensor, which can measure body temperature using a non-contact mode. The results indicate that the CNT yarn can be used to develop a wide range of environment-friendly, low-cost and lightweight paper-based flexible devices for wearable applications in temperature and respiratory monitoring, and personal healthcare.