Chemical sensors based on SAW resonators working at up to 1 GHz

We have investigated SAW chemical sensors working at 434 MHz and at 1 GHz, the latter frequency being the highest value reported in this context to date. In particular, the theoretical claim that the gas sensitivity is proportional to the frequency has been checked experimentally. The results of a noise characterization clearly show that the detection limit decreases with frequency even when noise is taken into account. By using molecular cavity compounds such as calixarenes, cyclodextrines and cyclophanes or "molecularly imprinted" polymers as chemically sensitive coatings, sub-ppm traces of halogenated and aromatic hydrocarbons such as toluene or xylene have been detected under ambient conditions.