Introduction Of QCMS Sensor
AT quartz crystal microbalance sensors (QCMS) are becoming into a good alternative analytical method in a great deal of applications, with a resolution comparable, in many cases, to chemical techniques used for detecting species and suitable for fluids physical properties characterization, though simpler and much less expensive.
However, an appropriate evaluation of this analytical method requires recognizing the different steps involved in order to be conscious of their importance and to avoid the possible error propagation if the appropriate care is not taken.
The three steps involved in a QCMS Sensor system are :
- Measurement of the appropriate parameters of the resonator. This includes a suitable electronics and cell interfaces for a specific application;
- Extraction of the effective parameters related to the model selected for the application (2-, 3- or 4-layer model). This is one of the most complicated steps, including mathematical algorithm combined with appropriate measurements in step 1. The most typical situations correspond to 3 layer model, although the analysis of 4-layer model is interesting for understanding the measurements resulting from intermediate processes which occur during the experiment; and
- Interpretation of the physical, chemical or biological phenomena responsible for the change in the effective equivalent parameters of the selected model. This is the last step and the final role of the system.
In this chapter we will focus on step 1, explaining the limitations of different electronic interfaces in relation to the application. In this case, the application will be evaluated as a function of a change in the measuring parameters. Thus, it is first necessary to define the parameters of the quartz crystal resonator (QCR) system to be measured.