Humidity sensors based on cross-linked poly(ionic liquid)s for low humidity sensing

Low humidity detection has been a great challenge in the field of humidity sensing. In recent years, polyelectrolytes have been proven to be promising materials for highly sensitive humidity sensors. In this work, cross-linked poly(ionic liquid)s (PILs) were prepared for low humidity detection. The strong hydrophilicity of PILs contributes to humidity sensing while the cross-linked structure guarantees the stability of the sensing film. The optimized sensor shows high response (48.0) in 5–35% RH, with short response/recovery time (1 s/10 s) and a small humidity hysteresis (0.2% RH). The possible sensing mechanism of the sensors was discussed. •Cross-linked poly(ionic liquid)s were used as low humidity sensitive materials.•The optimized sensor shows high response in 5–35% RH.•The optimized sensor has short recovery time and small humidity hysteresis.•The introduction of glycerol could reduce the impedance of the sensor.