Detection of Low Humidity Using Three-Dimensional DMC Network Structure

The detection of low humidity levels remains a great challenge in relative humidity (RH) sensing technologies. In this work, methacryloxyethyl trimethyl ammonium chloride (DMC) was coated around SiO2 microspheres to form DMC/SiO2 composite microspheres, which were self-assembled into a three-dimensional (3D) network structure for low humidity detection. The hydrophilic nature of the DMC component enhances the adsorption capacity for water molecules even at ultra-low humidity levels (1–18.6% RH), while the 3D network structure provides abundant channels for fast water molecule transport, facilitating rapid response and recovery processes. The optimized sensor shows high response (13.544%) in 1–18.6% RH, with short response/recovery time (6 s/10 s) and a small humidity hysteresis (1.4% RH). Such high performance shows that this type of sensor has great potential for application in widespread fields, such as electricity, semiconductor manufacturing, pure gas supply, aerospace, and pharmaceutical formulations.