Development of Quartz Crystal Microbalance (QCM) sensor for quantification of suspended particulate matter (SPM) and its evaluation by three-dimensional numerical modeling and experiments

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For the purpose of developing the suspended particulate matter (SPM) sensor, three-dimensional finite element modeling was examined, and some evaluation experiments were carried out. On the sensitivity for the adsorbate quantity, both agreed almost on the analytical result according to three-dimensional finite element model and two-dimensional model limited to the principal vibration mode. Mode coupling problem of multiple-channel QCM was analyzed using the two-dimensional finite element model. Not only that it establishes the trench between each vibrators but also that to absorb the vibration by the insertion in the trench of the damper material is effective were proven in order to avoid the mode coupling. Using the three-dimensional finite element model, frequency-temperature characteristics of the vibrator of AT-cut and Y-cut were analyzed. By calculating the temperature coefficient of the equivalent circuit parameter, it became possible that the action in constituting the SPM sensor circuit using the device under design was analyzed by the circuit simulator. Simulation and parameter identification method of adsorption film using the optimization algorithm and the transmission line model was developed. This identification method can be used for correcting measurement error by the existence of the film which adsorbs SPM. Measurement and detecting particle experiment of frequency-temperature characteristic of the AT cut vibrator were carried out. The validity of the numerical simulation of temperature characteristic was shown by the measurement of the temperature characteristic. In the detection experiment, it was confirmed that the particle detection by QCM is possible. The result of the basic development of the numerical simulation technology in this study seems to be useful for developing the SPM sensor.