Sensitivity of the smell detection quartz resonator with a sensitive membrane of squalene or Japanese lacquer for water molecule

For research on aromatherapy, an apparatus to measure type of smell and strength should be developed. Basic research for the detection of odorous molecules requires examination of the effect of water molecule in air. Especially, the authors examined the change of electrical characteristics (impedance Z and resonant frequency f) of AT-cut quartz resonator on which a sensitive membrane of Japanese lacquer or squalene had been placed. Changing ratios of _Z/Z for ethanol molecule and water molecule were positive for the Japanese lacquer membrane, but it was negative for the squalene membrane. However, changing ratios of _f/f were positive for both membranes. The sensitivity for water molecules by the squalene membrane for _f/f was about 100 times bigger than that by the Japanese lacquer, and the former was about 8 times bigger for _Z/Z. Theses results indicated that in order to decrease the effect of water molecules in smell detection, the Japanese lacquer membrane was better than the squalene membrane.