Construction of piezoelectric sensors

A quartz plate equipped with a gold electrode on each face can detect the adsorption of mercury vapor on the gold. A carbon monoxide sensor can therefore be constructed since this gas reacts with mercury oxide at 210 liberating mercury vapor [224] which is detectable with the piezoelectric sensor. Similarly, the deposition of copper complexes on a quartz crystal is used to detect organophosphates [225] such as diisopropylmethylphosphonate (DIMP), and modified cyclodextrins are us to detect benzene vapors [226]. The piezoelectnc sensor is also used in the liquid phase to monitor the viscosity of fluids and gelation, and deduce, for example, the concentration of fibrinogen [227]. 

Enzymes can be deposited instead of inorganic compounds. The inhibition of cholinesterase by complexation with organophosphate 

Finally, certain macromolecular materials have the property of swelling up under the action of parameters of a physical (temperature. 

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