Investigation on the frequency dependence of lateral field excited quartz crystal resonator on liquid permittivity

This research reports a high frequency lateral-field-excited quartz crystal resonator sensor (LFE-QCR) arranging the two excitation electrodes on one side. It is well known that when used in liquid LFE QCR could detect both mechanical and electrical property[1]. However, the mechanism and exact relationship between the liquid permittivity and the frequency shift is not clear. In this paper, two LFE-QCR chips with different but both highly fundamental frequency are used to investigate the frequency dependence of LFE-QCR on liquid permittivity. And in order to observe the real-time change of frequency, a flow-injection-based system is established, which consist of a syringe pump, a sample injector, and a custom-made micro-flow cell. Sensitivity of LFE-QCR for permittivity has been confirmed by using different concentrations of 2-propanol. In addition, according to the reliable experiment data, we present an approximate relationship between frequency shift and permittivity.