A Pair of SAW Devices-Based Viscosity Measurement for a Small Amount of Sample Volume

This research presents a new method to measure viscosity for a small amount of sample volume using a pair of surface acoustic wave devices. This method gives a real-time and noninvasive measurement and generates rotational motion of the liquid sample. To verify the proposed method, we conducted an experiment with aqueous sucrose solutions. The surface acoustic wave devices were designed to operate with small sample volumes and offer precise control over liquid manipulation by generating acoustic waves through interdigitated transducers. In the experiment, sucrose solutions ranging from 0% to 30% w/v were tested to investigate the influence of concentration on liquid viscosity and dynamic behavior. Rotational motion was induced in the liquid samples by applying alternating voltages, and the resulting movements were analyzed using image analysis software to calculate angular velocity. The experimental system also recorded resonance frequency shifts corresponding to different concentrations. Results showed a clear correlation between increased sucrose concentration and higher viscosity. The higher the concentration, the greater the voltage required to initiate rotation, and it resulted in reduced rotational velocity. A strong linear relationship (R² = 0.9618) was observed between the inverse of angular velocity and solution viscosity, confirming the feasibility of using a pair of surface acoustic wave devices for indirect viscosity measurement. The proposed surface acoustic wave device-based system offers a compact, efficient, and sensitive method for liquid characterization, with potential applications in biomedical diagnostics, chemical sensing, and lab-on-chip platforms.