Quartz-crystal sensors for biosensing and chemical analysis.

The principle and applications of quartz-crystal sensors based on the three basic concepts for mass, viscosity, and viscoelastic changes are reported. In the general discussion the realization of a resonant frequency-resonant resistance diagram is described in detail. As an example of application to mass sensing, gas sensing with a carbon-coated quartz crystal is reported. Determination of the blood coagulation factor is used as an example of the application to viscosity sensing. As an example of viscoelastic measurement, an ion-exchange polymer-coated quartz crystal is investigated to show that viscoelasticity changes more than mass in the transport process. The possibility of developing new biosensors and chemical sensors is discussed on the basis of these results.