Design, Fabrication, and Characterization of PVA-SnO2 based Humidity Sensor

In this research, humidity sensors based on Polyvinyl Alcohol (PVA)-Tin Oxide (SnO2) have been designed and fabricated using thick film technology. Fabrication of the sensor devices was conducted using screen printing techniques on Alumina (Al2O3) substrates with Silver (Ag) as the electrode material. The number of fingers on the electrodes was varied from 4 to 8 to obtain different resistance values of the sensor. SnO2 was added to the PVA sensing layer with variations in the composition of 1:1 and 1:2. The fabricated sensor devices have been tested under various humidity points and temperatures inside a custom chamber having a reference humidity sensor. The results showed that all sensors responded well to humidity variation by decreasing in resistance values as the relative humidity (RH) points were increased from 50 to 90%. However, temperature variation from 25 to 35 °C has resulted in higher responses for all sensors at each RH point. Although the sensors with composition of the sensitive layers of 1:2 had shown more sensitive responses compared to those with 1:1 composition, overall sensors have demonstrated fast responses to humidity variations with response time of less than 3 min (167 s) and recovery time of less than 10 min (559 s).