Physical properties-based microparticle sorting at submicron resolution using a tunable acoustofluidic device

Abstract

Acoustophoretic manipulation has been drawing great attention in the area of microfluidics-based cell/particle isolation and sorting due to its advantages of high biocompatibility, contactless manipulation and fabrication simplicity. Most label-free microfluidic particle sorting methodologies are solely based on a single physical property for example particle size, density or material composition, which hinder their broad usage in various applications. In this work, we demonstrate a tunable acoustofluidic device for continuous particle separation based on multi-physical properties such as size, density, compressibility and speed of sound. The tunable acoustofluidic system utilizes an elasto-inertial particle focusing technique to align particles into a single line and integrates a slanted interdigitated transducer (SFIT) that generates a tunable travelling surface acoustic wave to separate the particles with improved sorting accuracy and efficiency. The presented acoustofluidic sorting device allows the generation of a variable frequency from 99 MHz to 247 MHz corresponding to the wavelength 40 μm and 16 μm using the SFIT. We have successfully sorted 5.26 μm from 5 μm polystyrene particles at 90 % accuracy with a relative size difference of 5.2 %. Furthermore, a theoretical analysis of acoustic radiation force (ARF) exerted on rigid particles of different materials (i.e., polystyrene, PLGA, PMMA) is presented. Based on the optimal frequencies identified in the theoretical analysis, we have also experimentally demonstrated effective sorting of the three above-mentioned materials of particles with the same particle size.