The ammonia sensing properties of single-layer graphene synthesized by chemical vapor deposition (CVD) were studied. The Au interdigitated electrode (IDE) was prepared by microelectromechanical systems (MEMS) technology, and then, the single-layer graphene was transferred to the IDE by wet transfer technology. Raman spectroscopy was used to monitor the quality of graphene films transferred to SiO₂/Si substrates. Moreover, the theory of graphene’s adsorption of gases is explained. The results show that gas sensing characteristics such as response/recovery time and response are related to the target gas, gas concentration, test temperature, and so on. In the stability test, the difference between the maximum resistance and the minimum resistance of the device is 1 ohm without ammonia, the change is less than 1% of its initial resistance, and the repeatability is up to 98.58%. Therefore, the sensor prepared with high quality single-layer graphene has good repeatability and stability for ammonia detection.

In this paper, to address the problems of large blood draws, long testing times, and the inability to achieve dynamic detection of invasive testing for diabetes, stemming from the principle that type 1 diabetic patients exhale significantly higher levels of acetone than normal people, a FAIMS-MEMS gas sensor was designed to detect acetone, which utilizes the characteristics of high sensitivity, fast response, and non-invasive operation. It is prepared by MEMS processes, such as photolithography, etching, and sputtering, its specific dimensions are 4000 μm in length, 3000 μm in width and 800 μm in height and the related test system was built to detect acetone gas. The test results show that when acetone below 0.8 ppm is introduced, the voltage value detected by the sensor basically does not change, while when acetone gas exceeds 1.8 ppm, the voltage value detected by the sensor increases significantly. The detection accuracy of the sensor prepared by this method is about 0.02 ppm/mV, and the voltage change can reach 1 V with a response time of 3 s and a recovery time of 4 s when tested under 20 ppm acetone environment; this has good repeatability and stability, and has great prospects in the field of non-invasive detection of type 1 diabetes.

Based on the humidity testing requirements in different environments, this paper investigates the humidity sensitivity of reduced graphene oxide (rGO)-sodium dodecyl sulfate (SDS) composite film humidity sensor. In the experiments, rGO-SDS dispersions with a concentration of 5 mg/mL were prepared, and a microelectromechanical system (MEMS) process was used to prepare the interdigital electrodes. The dispersions were then drop-coated on the interdigital electrodes and dried on a heated plate at 100 °C. The surface characteristics of the rGO-SDS films transferred onto SiO₂-Si substrates were analyzed by scanning electron microscopy, raman spectroscopy and atomic force microscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, and tested by a correlation system, which showed a linear relationship between humidity variation and the resistance variation of the sensor in the ambient humidity range of 25–95% RH. At room temperature, the linearity of the sensor is about 0.98431 and the sensitivity is about 11.41432 Ω/% RH. At 100 °C, the correlation of the sensor is about 0.95046 and the sensitivity is about 1.0145 Ω/% RH; with a response time of only 9 s at ambient humidity from 25% RH to 95% RH, the sensor has very good repeatability and stability.

The steam generator (SG) as a key piece of equipment in nuclear power plant servers for both primary and secondary systems. SG tube rupture (SGTR) events occasionally occur during pressurized water reactor operation and cannot be completely avoided. However, traditional leak monitors (such as the N-16 method) are not sensitive to small leak rate changes, and hence cannot be used for low-level leak rate detection under incipient fault conditions and are limited to post-accident analysis of significant releases. In this study, the utilization of Ti₃C₂T_x MXene for monitoring the micro rupture phenomenon of water vapor escaping from U-shaped tubes in a SG is reported for the first time. The experimental results demonstrate that the TiO₂@Ti₃C₂T_x, after undergoing partial oxidation for 2 hours, has a significantly enhanced gas sensing capability towards water vapor in an argon environment between 100 and 300 °C. In addition, its water vapor response time at as low as 100 ppm at 300 °C is less than 3 seconds and has excellent repeatability. The layered Ti₃C₂T_x MXene is beneficial for the adsorption and diffusion of water molecules, making it an excellent platform for conductive transport and carrier collection. TiO₂ nanoparticles formed by partial oxidation provide numerous gas adsorption sites, and the interlayer insertion of water molecules facilitates the interaction between water vapor and charged –OH groups in MXene. This behavior leads to a decrease in the dielectric constant and an increased electrical resistance due to an increased activation energy for electrons/holes transitioning to a free state. TiO₂@Ti₃C₂T_x nanosheets exhibit promising potential for trace water vapor detection and high-temperature environment sensing. Given the low concentration response and high safety, this type of water vapor sensor has great potential for early diagnosis of SGTR accidents.

Here we report an approach to fabricate micro-mask/micro-channels using water-soluble fiber poly (vinyl alcohol) (PVA). The scheme is a simple, environmentally friendly, and low-cost technology, that can realize the preparation of micro-mask/micro-channels on different substrates. Scanning electron microscope (SEM) and optical microscope (OM) are used to observe surface morphology and measured fiber diameter. We showed that a variety of micro-mask/micro-channels can be easily controlled by changing the swelling temperature and time of the PVA fiber. The swelling temperature was varied from 25 °C to 50 °C, the diameter of the fiber increased by 9.5 μm, and the diameter and volume swelling rates reached 59.38% and 154%, respectively. Meanwhile, with the increase in swelling time, the diameter and volume swelling rate showed the same increasing trend. Additionally, we used the PVA fiber as a micro-mask to prepare the micro-channel on the WSe₂ surface and verified the feasibility of the PVA fiber to prepare micro-mask/micro-channels by testing the electrical properties of the WSe₂ sample. Finally, we also verified the feasibility of the above methods to fabricate micro-mask/micro-channels on different substrates such as conductive fibers, PDMS, and WSe₂/SiO₂Si, and proposed to realize nano-scale patterning through direct electrospinning. Therefore, it is expected to be more widely promoted in the future.