Surface acoustic wave humidity sensor based on TiO2 sensitive membrane

This paper reports the calibration of TiO2 membrane proposed as active material for acoustic humidity sensors. The prototype device has been prepared depositing the sensitive membrane by r.f. reactive magnetron sputtering technique onto a quartz substrate on which previously a surface acoustic wave (SAW) delay line has been photolitographically defined. The calibration of the sensor have been performed varying the humidity of the ambient from 10% to 80% at controlled temperature and measuring the changes produced in the physical properties of the membrane by the sorption and desorption of the humidity.