Response of Quartz Crystal Microbalance to Liquid Electrical Properties.

Quartz crystal microbalance (QCM) operating in liquid can detect not only liquid mechanical properties (liquid density and viscosity) but also liquid electrical properties (liquid dielectric constant and conductivity). However, the relevant research so far has mainly focused on the liquid conductive property and mostly used relative values, which cannot fully reflect the response of QCM to liquid electrical properties. To study the effect of the electrical field scattering on the QCM response to liquid electrical properties and whether there is a coupling between the mechanical, dielectric, and conductive properties, reference groups for excluding the liquid mechanical effect were set up; solutions (isopropanol/water) with different dielectric constants and conductivities were adopted; static capacitance of the QCM covered with the isopropanol/water solutions was measured. The results indicate that the electrical field scattering plays an important role in the sensitivity of QCM to the dielectric property of liquid. There may be no, or very little, coupling between mechanical and electrical properties, but there is a coupling between dielectric and conductive properties at low conductivity, while at high conductivity, the conductive property is the dominant factor. The results are meaningful for understanding the multi-property sensing of QCM in the liquid phase.