Inertial Microfluidic Separation of Cell Clusters from Blood Cells in Meandering Channels

Inertial microfluidics is well established for separating particles and cells by size and mechanical properties; however, its application for isolating cell clusters from single blood cells in meandering channels remains largely unexplored. This study demonstrates the potential of inertial focusing in S-shaped meandering channels to separate two-cell clusters from single cells.

We first analyzed the cumulative secondary transport using passive-tracer trajectories recorded at phase-matched sections of repeated S-shaped periods. This Lagrangian analysis revealed four recurrent transport regions that help explain the observed size- and shape-dependent focusing behavior. We further developed a computational model, validated against experimental data in a nine-section meandering microchannel, which accurately predicts the distinct focusing positions of 8μm and 15μm particles-characteristic sizes of human red blood cells (RBCs) and leukocytes. The model was further validated against experiments with red blood cells and the MCF7 cell line, reproducing the observed focusing modes and transverse focusing positions.

Subsequently, we evaluated in silico the separation of two-cell clusters (formed by two adhered 8μm or 15μm cells, modeling circulating tumor cell clusters or leukocyte aggregates) from single blood cells across six microchannel designs of three varying widths and two heights of the channel. For different cell mixture compositions, we provide specific guidelines for optimizing channel geometry and flow velocity to achieve high-purity separation.

This work establishes a systematic framework for designing inertial microfluidic devices to isolate cell clusters using meandering microchannels.