Superhydrophilic CuO nanowire QCM humidity sensor with horsefly-inspired self-cleaning ability applied for non-contact detection

Abstract

Humidity sensors are crucial for a variety of applications, such as biomedicine and semiconductor fabrication. It is still a formidable challenge to achieve a humidity sensor with high sensitivity and anti-pollution ability. Inspired by the horsefly eye structure, we propose a superhydrophilic CuO nanowire quartz crystal microbalance humidity sensor covered by a micro-pit array, which can achieve outstanding self-cleaning properties. The physicochemical property of the sensing materials was characterized in situ using SEM, XRD, and XPS. The sensing characteristics of the specimen towards water molecules were studied using quartz crystal microbalance with dissipation monitoring, showing a high sensitivity of 82.5 ± 7.7 Hz/%RH. Molecular dynamics simulation and Brunauer–Emmett–Teller nitrogen sorption analysis were conducted for revealing the superhydrophilicity mechanism of CuO nanowires. Subsequently, a CuO nanowire humidity-sensing model was established, which was verified by both theoretical calculations and experiments. A smart non-contact sensing system based on the sensor was constructed, and the humidity intensity of human breath and fingers were detected. This work demonstrates the brilliant properties of superhydrophilic CuO nanowires for non-contact sensing applications, providing new solutions for medical health monitoring, industrial environment detection, and human-computer interaction.