Separation of sub-micron particles from micron particles using acoustic fluid relocation combined with acoustophoresis
Acoustophoresis has gained increasing attention as a gentle, non-contact, and high-throughput cell and particle separation technique. It is conveniently used to isolate and enrich particles that are greater than 2 μm; however, its use in manipulating particles smaller than 2 μm is limited. In this work, we present an alternative way of using acoustic forces to manipulate sub-micrometer particles in continuous flow fashion. It has been shown that acoustic forces can be employed to relocate parallel laminar flow streams of two impedance-mismatched fluids. We demonstrate the separation of sub-micron particles from micron particles by the combination of acoustophoresis and acoustic fluid relocation. The micron particles are focused into the middle of the flow channel via primary acoustic forces while sub-micron particles are moved to the side via drag forces created by the relocating fluid. We demonstrate the proof of the concept using binary mixtures of particles comprised of sub-micron/micron particles, micron/micron particles, and bovine red blood cells with E. coli. The efficiency of the particle enrichment is determined via flow cytometry analysis of the collected streams. This study demonstrates that by combining acoustic fluid relocation with acoustophoresis, sub-micron particles can be effectively separated from micron particles at high flow rates and it can be further implemented to separate binary mixtures of micron particles if the volumetric ratio of two particles is greater than 10 and the larger particle diameter is about 10 μm. The combined method is more appropriate to use than acoustophoresis in situations where acoustic streaming and differences in acoustic impedance of fluids can be of concern.
KeywordsAcoustophoresis Acoustic fluid relocation Particle separation Microfluidics
Research reported in this publication was supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20GM103451. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Los Alamos National Laboratory (Contract DE-AC52-06NA25396) and Sandia National Laboratories (Contract DE-AC04-94AL85000).
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Conflict of interest
Gayatri P. Gautam and Menake E. Piyasena declare that they have filed a patent application on this technology that uses principles discussed here. Rubi Gurung and Frank A. Fencl declare no competing interests.
- 17.Gor'kov L. On the forces acting on a small particle in an acoustical field in an ideal fluid. Sov Phys Dokl. 1962;6:773–5.Google Scholar
- 39.Weigl BH, Holl MR, Schutte D, Brody JP, Yager P. Diffusion-based optical chemical detection in silicon flow structures. Proceedings of the μTAS; Nov 19–22, 1996. Basel, Switzerland p. 174–84.Google Scholar