MXene-Coated Planar Microwave Resonator Sensor for Ultrasensitive Humidity Monitoring

This letter presents a microwave sensor based on an electric-inductor capacitor (ELC) resonator structure interfaced with 2-D transition-metal carbides (Ti3C2Tx MXene) for ultrasensitive monitoring of relative humidity (RH). The sensing zone utilizes an interdigitated pattern combined with an MXene film to enhance field distribution, which creates a larger contact area for more sensitive humidity detection. The binding energy of water molecules is estimated high on the surface of the designed sensor via MXene-OH termination using density functional theory (DFT) simulation, which depicts a small bond length. In addition, the resonant frequency of the developed sensor resonates at 4.1 GHz, which linearly changes with the RH ranging from 10% to 90% with a high sensitivity of 1.04 MHz/%RH and 30 mdB/%RH. The sensor's maximum relative standard deviation (RSD) of 0.011% and 0.120% with a low standard deviation value exhibit the repeatability of the designed humidity sensor. Thus, the achieved results validate the performance of the developed MXene-coated microwave resonator sensor for humidity monitoring applications demanding high sensitivity.