Waterproof, stretchable and wearable corrugated conductive carbon fiber strain sensors for underwater respiration monitoring and swimming instruction

Respiration is one of crucial vital signs, which can be used for health assessment and sports management. Flexible resistive strain sensors provide an opportunity to monitor personal respiratory behaviors in real time due to high sensitivity, good linearity and fast response. However, there are some critical issues with the resistive strain sensor, such as strain mismatch, poor contact properties and moisture sensitivity, which easily cause unexpected electrical response, limiting its application scenarios. Here, a novel stretchable carbon fiber strain sensor is developed by a simple structural design, which endow the device with a remarkable linearity (R2=0.99601 in 0–40 % tensile strain), excellent anti-jamming performance, long-term durability, and waterproofness. Moreover, a sophisticated wearable respiratory monitoring system is further developed, which can not only precisely distinguish diverse respiratory patterns to enhance the accuracy in early illness diagnosis but also remotely capture real-time breathing information during swimming for guiding swimming training. It demonstrates that our stretchable resistive strain sensor has an enormous application potential in wearable electronics and smart clothing for health monitoring and training guide.