Developing conductive fabric threads for human respiratory rate monitoring

Real-time monitoring of the respiration rate in everyday life enables the early detection of various diseases and disorders that can cause a life-threatening incident. In this article, a passive sensor for real-time monitoring of the human respiration rate is proposed. The sensor is deployed on a chest strap to accurately acquire the respiration rate data and display it on a smartphone through Bluetooth communication. The sensor consists of a stretchable fabric substrate impregnated with silver Nano-particles through drop-casting at ambient conditions. The proposed passive sensor provides a change in electrical resistance against applied strain due to shrinkage of the conducting threads and resets to the initial resistance value when released. The resistance modulation phenomenon is exploited for the respiration sensing application. The demonstrated sensor is 4 × 20 mm2, however, the dimensions can be changed according to the application and requirements. At rest position, resistance is 180 Ω and at 16% stretching, the resistance goes down to 70 Ω. The proposed device is characterized by mechanical, electrical, and surface morphology. The proposed sensor can be a good candidate for the respiration sensing application in wearable electronics.