Experimental assessment and modeling of acoustophoretic particle trajectories

Abstract

The field of acoustofluidics, the employment of acoustic forces in microfluidic systems, is receiving growing attention for use in biomedical applications due to its use for label-free and non-invasive separation and manipulation of cells and other biological particles. The field is young but has over the last decade undergone an important development towards clinical and industrial application, in particular due to an improved understanding of the underlying fundamental physical aspects. Here, theoretical modeling and experimental assessment of acoustophoretic particle trajectories have played an essential role, e.g., for the measurement of the in situ pressure amplitudes and resonance quality factors or for the understanding of the critical particle size for which the acoustophoretic particle motion is dominated by the acoustic streaming drag or the primary acoustic radiation force. These phenomena are typically of complex three-dimensional character and can only be fully understood through three-dimensional quantification such as through three-dimensional tracking of the acoustophoretic particle motion, e.g., via the General Defocusing Particle Tracking method. The importance of three-dimensional particle tracking will be demonstrated by application to the acoustophoretic particle motion in soft-walled polymer chips driven by surface acoustic waves as well as in hard-walled square glass capillaries driven by bulk piezo transducers.