Capacitance-type MWCNTs/SiO2 humidity sensor based on capillary condensation and percolation theory

A capacitance-type MWCNTs/SiO2 composites humidity sensor based on capillary condensation and percolation phenomenon was developed in this paper. To study the model of this humidity sensor, the porosity structure of the sensing film (MWCNTs/SiO2) was observed by SEM image, and the pore volumes in MWCNTs/SiO2 film at different pore radius were investigated by an Accelerated Surface Area and Porosimetry System. The model of the MWCNTs/SiO2 humidity sensor was built based on the capillary condensation and percolation theory. To verify the sensor model, MWCNTs/SiO2 humidity sensors were presented and the sensors capacitances were tested under different RH. According to the testing results, the sensor with MWCNTs concentration of 1 wt% has the best linearity (about 5.2%), and the sensitivity of the sensors is about 673pF/%RH.