Flexible screen-printed sic-based humidity sensors.

Humidity sensors are essential components in modern technology, spanning applications from residential appliances to the Internet of Things (IoT). However, conventional commercial sensors are typically rigid, constrained by narrow relative humidity (%RH) operating ranges, and require complex fabrication processes. In this study, we present a highly sensitive cubic silicon carbide (3C-SiC) nanoparticle-based relative humidity sensor, fabricated via serigraphic printing on to 5 mil thick flexible polyimide (Kapton^®) substrate. Devices are tested across a broad humidity range of 10-90%RH at ambient temperature and their performance is evaluated in a controlled humidity chamber. The sensor exhibits a robust response of 45.2% R/R₀, with a sensitivity of 5.34 Ω/%RH, an adsorption time of 18 seconds, and a desorption time of 46 seconds. Additionally, the device demonstrates low hysteresis of 6.5% at 60%RH, with excellent repeatability and stability over 3.5 hours of continuous cycling. To showcase their potential for real-world applications, the printed sensors are integrated into a commercial KN95 mask for monitoring respiration parameters, such as respiration rate. This integration highlights the potential for future exploration in human health monitoring, utilizing fully printed, low-cost sensing devices.