A flexible and wearable NO(2) gas detection and early warning device based on a spraying process and an interdigital electrode at room temperature

Flexible sensors used to detect NO(2) gas generally have problems such as poor repeatability, high operating temperature, poor selectivity, and small detection range. In this work, a new spraying platform with a simple structure, low cost, and good film-forming consistency was designed and built to make a sensitive film (rGO/SnO(2)) for NO(2) gas sensors. The relationship between the solid content of rGO and SnO(2) nanoparticles, annealing temperature, and sensor performance was studied. The results show that the interdigital electrode-sensitive film formed by spraying 0.25 ml of a 0.4 wt% rGO/SnO(2) mixture and annealing at 250 °C exhibited the best comprehensive performance for NO(2) detection. The sensor’s response value for 100 ppm NO(2) gas was 0.2640 at room temperature (25 °C), and the response time and recovery time were 412.4 s and 587.3 s, respectively. In the range of 20–100 ppm, the relationship between the response and NO(2) concentration was linear, and the correlation coefficient was 0.9851. In addition, a soft-monitoring node module with an overlimit warning function for NO(2) gas was designed and manufactured based on flexible electronics. Finally, the flexible sensor and node module were embedded into woven fabric that could be used to make a mask or a watch that could detect NO(2) gas, realizing the practical application of flexible NO(2) gas sensors in the field of wearable electronics.