Abstract

Inertial Focusing in Triangular Microchannels for Flow Cytometry

Ian Papautsky, Professor of Bioengineering, Co-Director, NSF Center for Advanced Design & Manufacturing of Integrated Microfluidics, University of Illinois at Chicago

In the past two decades, microfluidics has become of great value in precisely aligning cells or microparticles within fluids. Microfluidic techniques use either external forces or sheath flow to focus particulate samples, and face the challenges of complex instrumentation design and limited throughput. The burgeoning field of inertial microfluidics brings single-position focusing functionality at throughput orders of magnitude higher than previously available. However, most inertial microfluidic focusers rely on cross-sectional flow-induced drag force to achieve single-position focusing, which inevitably complicates the device design and operation. This work presents a microfluidic device that takes advantage of asymmetric velocity profile in a low aspect ratio triangular microchannel to focus cells and microbeads into a single position with high efficiency, and without the need for secondary flow, sheath flow or external forces. The device was further integrated with a laser counting system to form a sheathless flow cytometer, and demonstrated to count at ~1,000/s throughput and <10% variability. Cells can be completely recovered and remain viable. This approach offers a number of benefits, including simplicity in fundamental principle and geometry, convenience in design, modification and integration, flexibility in focusing of different samples, high compatibility with real-world cellular samples as well as high-precision and high-throughput single-position focusing.