Acoustofluidics at Audible Frequencies—A review

Acoustofluidics is a term describing the class of phenomena in which mechanical or acoustic vibrations induce a deformation or a flow in a fluid. Many deficiencies in our understanding of these phenomena remain to be addressed, with respect to the fundamental theoretical framework as well as in numerous applications. In this regard, the frequency of external forcing is a key parameter. Owing to the low cost, substantial magnitude, and versatility associated with acoustofluidic phenomena at audible frequencies, studies of these phenomena in the audible range have emerged with increasing amount in recent years and have attracted considerable attention. However, compared with studies focusing on the ultrasonic frequency domain, critical features and information specific to audible acoustofluidics remain dispersed across many independent publications, and a systematic integration of the literature on this topic is necessary. Accordingly, this review summarizes the basic theory and methods for generating vibrations in the audible range, presents various applications thereof in biology, chemistry, and other fields, and provides a high-level overview of the current status of the topic to motivate developing interesting proposals for further research in this field of study.