Study on thick film humidity sensor using PVA-Gelatin-SnO2 sensing layer

Abstract

In this research, various compositions of sensing layers have been studied for their use in humidity sensors. Materials used for the sensing layers were Polyvinyl Alcohol (PVA), Gelatin, and Tin Oxide (SnO2). The sensor device was designed and fabricated using thick film technology through screen printing techniques on Alumina (Al2O3) substrates, with Silver-Palladium (AgPd) as the electrode material. The number of electrode fingers was varied to obtain optimum sensor resistance values. The PVA sensing layer was combined with gelatin and various compositions of SnO2 to study their effect on the sensor response to humidity. The sensor devices were tested in a custom chamber with varying humidity levels from 50% to 90%. The results showed that the sensor based on the PVAGelatin-SnO2 (PGS) sensing layer had higher resistance values and more sensitive responses than the sensor without gelatin. The hydrophilic nature of gelatin has been found to contribute significantly to the water sensitivity of the matrix. In addition, the difference in the number of fingers of the sensor electrode and the addition of SnO2 also affect the resistance value.