Acquiring fluorescence decay kinetic measurements with on-chip acoustic focusing cytometry

Flow cytometers are invaluable tools that can quantitatively analyze and separate cells with respect to a cell’s biophysical and biochemical properties. Conventional cytometers collect these physical and chemical properties in the forms of inelastic light scatter and fluorescence. Specialized cytometers came to fruition after several advancements; smaller, more efficient photodetectors, tunable laser diodes, and the advent of microfluidics. Our work focuses on the latter topic. Microfluidic-based flow cytometry is robust in single cell and single molecule detection. Recent studies have leveraged significant quantitative analysis from multiplexing in phenotyping experiments, rare events in highcontent screening assays and sorting. Multiplexing requires multiple color channels to capture and resolve the presented spectral data. Color compensation is needed to resolve emission spectra overlap and becomes difficult when 10+ colors are used. Rare event detection requires large volumes of sample to the effect of 109 cells and greater. The task becomes time and resource consuming because conventional flow is limited by linear flow velocities (50,000 events/second) and requires extensive amounts of sheath fluid. Lastly, collecting these events by conventional flow requires careful separation by means of fluorescence activated cell sorting (FACS). Most cell sorters are capable of high yields but use piezoelectric transducers that are not as biocompatible as once thought. Herein we present a time-resolved acoustofluidic flow cytometer that can theoretically surpass the linear velocity constraint, use acoustic focus to elevate biocompatibility and reduce resource consumption and eliminate the need for multiple color channels.