Graphene, GO, and Borophene: Innovations in QCM-Based Humidity Sensors for Enhanced Sensitivity

Humidity measurements are crucial in daily life as they influence human comfort, health, safety, and product quality. Quartz Crystal Microbalance (QCM) sensors, known for their fast response times and high sensitivity, offer a significant advantage in humidity sensing due to their ability to provide highly linear and accurate measurements. These sensors are particularly valuable because they enable real-time, precise humidity detection with minimal calibration, making them ideal for various applications. This mini-review highlights the significance of QCM sensors, focusing on the sensing layers made from nanomaterial fillers integrated into composite matrices. Typical QCM sensor surfaces are could be coated with highly conductive materials such as graphene, graphene oxide (GO), and borophene, which offer excellent humidity-sensing capabilities due to their two-dimensional allotrope structure and unique properties of carbon and boron. This review begins with a brief overview of humidity measurement principles and QCM sensor characteristics. It then explores a variety of materials used for preparing QCM sensing layers, discussing their advantages and disadvantages for humidity sensor applications. Finally, the review presents future perspectives on the development of layer-by-layer self-assembled conductive polymeric films, novel GO-based composite QCM humidity sensors, and borophene-based humidity sensors, illustrating their potential for multifunctional composites.