Investigations on the Time-Averaged Viscous Torque Acting on Rotating Micro Particles

Abstract

An analytical formulation is developed to predict the steady angular velocity for the rotation of a spherical particle driven by the time-averaged acoustic viscous torque. This time-averaged viscous effect is generated by an acoustic excitation of two orthogonal standing waves. Furthermore, the analytical formulations are verified by the experiments, where a macroscopic fluid cavity is excited by two piezoelectric transducers to build up two orthogonal standing waves. The experimental results with spherical micro particles show a good agreement with the analytical calculations on the rotation direction and the angular particle velocity. The prediction of the steady angular velocity and its influencing parameters is an important step for the further realization of applications.