A cyclo-acoustofluidic-separator for solution exchange with minimized concentration dilution

Acoustofluidic technology shows tremendous application potential in solution exchange due to its miniaturization, biocompatibility, and label-free property. However, the introduction of large volumes of sheath fluid causes severe sample dilution, imposing limitations in certain applications, such as continuous plasma exchange. To address the dilution issue caused by sheath fluid in acoustofluidic technology, this paper proposes a cyclo-acoustofluidic-separator, inspired by the structure of a cyclotron, to achieve iso-concentration solution exchange via multi-stage acoustic separation. The system combines acoustofluidic manipulation and passive hydrodynamic mechanism in a series of whirled microfluidic channel around standing surface acoustic wave fields, achieving particle transfer to the new medium with concentrations equivalent to 90.7% of the initial sample solution. Furthermore, the system achieves a particle sample throughput of 10 μl/min. It is expected to be able to process 1.5–2.5 ml blood volume within approximately 2–3 h, meeting the demands for plasma exchange of mice. Our system offers a novel solution to the dilution challenge of the acoustofluidic technology; thus, it is promising to provide more stable and reliable technical support for precise plasma exchange studies in small animal models and the potential development of specialized plasma exchange instruments for infants.