Application of low frequency mechanical resonators to liquid property measurements

Application of low-frequency mechanical resonators to liquid characterization is described. It is found that in a liquid environment the impedance of a low-frequency resonator changes according to theory developed for thickness shear mode (TSM) resonators regardless of different oscillation modes. The use of low-frequency resonators produces much higher sensitivity to liquid mechanical and electrical properties than known techniques. Viscosity density product, dielectric constant and conductivity are simultaneously measured for small liquid samples by exposing the tuning fork piezoelectric quartz resonator to the liquid sample and processing the frequency dependence of the resonator impedance. Tuning fork resonators give a possibility to use much lower oscillation frequency than usual (TSM) resonators, which makes them applicable to mechanical properties measurement of high molecular weight polymer solutions. The low cost of tuning fork resonators and simple low-frequency readout electronics give the possibility to build large arrays of sensors for parallel high throughput screening.