Measuring air humidity is important in many areas. However, conventional sensors in hygrometers have so far not been able to determine a very low water vapor content. Physicists at the University of Duisburg-Essen (UDE) and the Yuri Gagarin Technical University in Russia have now developed a new sensor. It detects even the smallest amounts of water molecules that sink to its surface. The detector is based on highly conductive materials known as MXenes.
source https://phys.org/news/2021-10-sensor-air-humidity.html