The development of a flexible and high-performance humidity sensor is essential to expand its new applications, such as personal health monitoring and early diagnosis. In this work, SnO₂/rGO nanocomposites were prepared by one-step hydrothermal method. The effect of rGO-doping on humidity sensing performance was investigated. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy were used to characterize the nanostructure, morphology and chemical composition of SnO₂/rGO nanocomposites. The SnO₂/rGO humidity sensitive film was prepared by electrospinning on a polyimide film modified with gold electrodes. The humidity test results show that different doping ratios of rGO have different effects on humidity sensing properties. Among them, the sensor with 2 wt% rGO-doping has a high sensitivity (37,491.2%) within the humidity range as well as the fast response time (80 s) and recover time (4 s). Furthermore, the sensor with 2 wt% rGO-doping remains good flexibility and stability in the case of bending (1000 times). The sensitivity of the 2 wt% rGO-doping sensor at the bending radius (8 mm and 4 mm) is 48,219% and 91,898%, respectively. More importantly, the sensor could reflect different breathing states clearly and track breathing intervals as short as 3 s. The SnO₂/rGO flexible humidity sensor with accuracy, flexibility and instantaneity as well as the facile fabrication strategy is conceivable to be applied in the potential application for human health real-time monitoring.

An absolute MEMS capacitance vacuum sensor with a full range of (1-1000) Pa has been designed, fabricated and tested. The working principle of the capacitance vacuum sensor is explained and its fabrication process is introduced. For obtaining high sensitivity, the sensor's pressure-sensing diaphragm with large width-to-thickness ratio is manufactured using the silicon-on-insulator (SOI). A silicon buffer block is adopted to improve the linearity of the sensor and prevent the pressure-sensing diaphragm from being damaged due to overload. The sensor is packaged by anodic bonding process in a certain high vacuum environment to form a sealed cavity, in which the vacuum degree is maintained by the non-evaporable getter (NEG) film deposited on the buffer block surface. The absolute pressure measurement of the packaged sensor has been performed with a vacuum measurement system. The tests results show that the capacitance-pressure curve is piecewise linear in the full range (1-1000) Pa. And the sensor exhibits high stability and reproducibility. The maximum sensitivity of the sensor is 33.03 fF/Pa, while the resolution can reach 0.5 Pa. Moreover, the temperature characteristic of the sensor has been evaluated, and it turns out that the effect of temperature on the sensor is quite small in a certain temperature range. [2020-0276]