Flexible and multifunctional humidity sensor based on Au@ZIF-67 nanoparticles for non-contact healthcare monitoring

To facilitate real-time monitoring and recording of humidity in the environment and to satisfy the requirement for strain performance in certain applications (such as wearable devices), this paper proposes an in-situ method for synthesising Au nanoparticles on ZIF-67. In this study, an Au@ZIF-67 composite humidity-sensitive material was combined with flexible polyethylene terephthalate interdigitated electrodes to create an Au@ZIF-67 flexible humidity sensor. The prepared samples were characterised using X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The humidity-sensitive properties of the sensor were investigated, and its monitoring capabilities in applications involving respiration, gestures, skin, and baby diapers were tested. The experimental results indicate that compared with a pure ZIF-67 humidity sensor, the Au@ZIF-67 (0.1Au@Z) flexible humidity sensor exhibits a 158.07% decrease in baseline resistance and a 51.66% increase in sensitivity to 95% relative humidity, and the hysteresis, response time, and recovery time are significantly reduced. Furthermore, the sensor exhibits excellent characteristics such as high resolution, repeatability, and stability. The obtained results regarding the material properties, humidity sensitivity, and practical application of non-contact humidity monitoring demonstrate that the prepared sensors exhibit excellent and comprehensive performance, indicating their broad prospects in wearable medical devices, wireless Internet of Things, humidity detection in complex environments, and intelligent integrated systems. Graphical abstract