Novel capacitance-type humidity sensor based on multi-wall carbon nanotube/SiO₂composite films

Abstract

A novel capacitance-type relative humidity (RH) sensor based on multi-wall carbon nanotube/SiO2 (MWCNTs/SiO2) composite film is reported. Details of the fabrication process, possible sensing mechanism and sensing characteristics, such as linearity and sensitivity, are described. The capacitance of the MWCNTs/SiO2 composite film shows typical concentration percolation behavior with increasing MWCNT loading. At loadings below the percolation threshold (1.842wt%), the sensor capacitance increases obviously with increasing MWCNTs. The water condensed in the MWCNTs/SiO2 layer can lower the percolation threshold and increase the sensor capacitance. The sensor with MWCNT concentration of 1wt% has the best properties. The sensor has a humidity sensitivity of about 673 pF/% RH and a linearity correlation of 0.98428. The response time of the sensor to RH is about 40 s and the recovery time is about 2 s.