Wearable Dual-Signal NH₃ Sensor with High Sensitivity for Non-invasive Diagnosis of Chronic Kidney Disease

NH3 gas in human exhaled breath contains abundant physiological information related to human health, especially chronic kidney disease (CKD). Unfortunately, up to now, most wearable NH3 sensors show inevitable defects (low sensitivity, easy to be interfered by the environment, etc.), which may lead to misdiagnosis of CKD. To solve the above dilemma, a nanoporous, heterogeneous, and dual-signal (optical and electrical) wearable NH3 sensor mask is developed successfully. More specifically, a polyacrylonitrile/ bromocresol green (PAN/BCG) nanofiber film as a visual NH3 sensor and a polyacrylonitrile/polyaniline/reduced graphene oxide (PAN/PANI/rGO) nanofiber film as a resistive NH3 sensor are constructed. Due to the high specific surface area and abundant NH3 binding sites of these two nanofiber films, they exhibit good NH3 sensing performance. However, although the visual NH3 sensor (PAN/BCG nanofiber film) is simple without the need of any detecting facilities and quite stable when temperature and humidity change, it shows poor sensitivity and resolution. In comparison, the resistive NH3 sensor (PAN/PANI/rGO nanofiber film) is of high sensitivity, fast response, and good resolution, but its electrical signal is easily interfered by the external environment (such as humidity, temperature, etc.). Considering that the sensing principles between a visual NH3 sensor and resistive NH3 sensor are significantly different, a wearable dual-signal NH3 sensor containing both a visual NH3 sensor and resistive NH3 sensor is further explored. Our data prove that the two sensing signals in this dual-signal NH3 sensor mask can not only work well without interference with each other but also complement each other to improve the sensing accuracy, indicating its potential application in non-invasive diagnosis of CKD.