The study of colloidal systems with TSM piezoelectric sensors

Colloids and suspensions represent a large group of fluids important in many biological and chemical applications. Mechanical and viscoelastic properties of colloids and suspensions, processes of sedimentation, mechanisms of interaction between particles, and interfacial processes involving interaction of particles with various surfaces are of special interest. In this paper we present the use of Thickness Shear Mode (TSM) resonant sensors for characterizing the kinetics of various phenomena accompanying the sedimentation process. The studied colloidal system which consisted of a polystyrene spheres of the size 1, 10 and 90 microns suspended buffered saline solution was tested with TSM resonators operating at the fundamental frequency of 5 MHz and its harmonics. The measured parameters included the sedimentation rate, and the changes in the viscoelastic properties of the medium as a function of time, concentration and the penetration depth of the probing acoustic shear wave. The obtained results showed that the TSM sensors can be used for a rapid and accurate monitoring colloidal processes in real time with high sensitivity and resolution.