Relocation of coflowing immiscible liquids under acoustic field in a microchannel

¹ Department of Mechanical Engineering, Indian Institute of Technology Madras - Chennai 600036, India
² Division of Nanobiotechnology, Department of Biomedical Engineering, Lund University 221 00, Lund, Sweden

Received: 19 September 2018
Accepted: 26 February 2019

Abstract

We report the dynamics of coflowing immiscible liquid streams exposed to an acoustic standing wave in a microchannel. Relocation of the liquid streams is experimentally demonstrated and a theoretical model that explains the underlying phenomena is presented. Our experiments and theoretical model suggest that the relocation phenomena are governed by the interplay between the primary acoustic radiation force F_ac and the interfacial tension force F_int —which is represented in terms of a new dimensionless number called “acoustocapillary number”, . Using various combinations of immiscible liquids, we show that relocation of the higher acoustic impedance liquid stream to the pressure node occurs above a critical acoustocapillary number . The understanding of the above phenomena provides a new paradigm related to the manipulation of immiscible liquids under acoustic field.