In this work, we demonstrate a sheathless acoustic fluorescence activated cell sorting (aFACS) system by combining elasto-inertial cell focusing and highly focused traveling surface acoustic wave (FTSAW) to sort cells with high recovery rate, purity, and cell viability. The microfluidic sorting device utilizes elasto-inertial particle focusing to align cells in a single file for improving sorting accuracy and efficiency without sample dilution. Our sorting device can effectively focus 1 μm particles which represents the general minimum size for a majority of cell sorting applications. Upon the fluorescence interrogation at the single cell level, individual cells are deflected to the target outlet by a ∼50 μm wide highly focused acoustic field. We have applied our aFACS to sort three different cell lines (i.e., MCF-7, MDA-231, and human-induced pluripotent stem-cell-derived cardiomyocytes; hiPSC-CMs) at ∼kHz with a sorting purity and recovery rate both of about 90%. A further comparison demonstrates that the cell viability drops by 35–45% using a commercial FACS machine, while the cell viability only drops by 3–4% using our aFACS system. The developed aFACS system provides a benchtop solution for rapid, highly accurate single cell level sorting with high cell viability, in particular for sensitive cell types.

Inertial microfluidics has been proven to be a powerful tool for high-throughput, size-based cell sorting in diverse biomedical applications. In the case of Candida-related sepsis, Candida species and major blood cells (i.e., red blood cells and white blood cells) have a size distribution of 3−5 and 6−30 μm, respectively. To effectively retrieve a majority of Candida species and remove most of the interfering blood cells for accurate molecular analysis, inertial sorting of micron-sized biological particles with submicron size difference is highly desired, but far unexplored till now. In this work, we present a new channel design for an inertial microfluidic sorting device by embedding microsquares to construct periodic contractions along a series of repeating curved units. This unique channel design allows us to enhance inertial lift force at the microsquare zone and produce localized secondary Dean flow drag force in addition to global Dean flow drag force. This inertial sorting device has successfully separated 5.5 μm particles from 6.0 μm particles with a recovery ratio higher than 80% and a purity higher than 92%, demonstrating a size-based inertial sorting at submicron resolution (i.e., 0.5 μm). We further applied this inertial sorting device to purify Candida species from whole blood sample for enhanced molecular diagnosis of bloodstream Candida infection and especially compared it with the commonly used lysis-centrifugation-based purification method (STEM method) by recovering two species of Candida (Cornus glabrata and Candida albicans) from Candida-spiked blood samples. Through quantitative polymerase chain reaction (qPCR) analysis, we found that our inertial sorting approach has nearly 3-fold improvement on the pathogen recovery than the STEM method at pathogen abundances of 10 3 cfu/mL and 10 2 cfu/mL. The present inertial sorting at submicron resolution provides a simple, rapid, and efficient pathogen purification method for significantly improved molecular diagnosis of bloodstream Candida infection.

Purification of bacteria from human blood samples is essential for rapid identification of pathogens by molecular methods, enabling faster and more accurate diagnosis of bloodstream infection than conventional gold standard...