"Fugaku" unveils new cell sorting principle

Osaka, Japan – Researchers have discovered a novel criterion for sorting particles in microfluidic channels, paving the way for advancements in disease diagnostics and liquid biopsies. Using the supercomputer "Fugaku," a joint team from The University of Osaka, Kansai University and Okayama University revealed that soft particles, like biological cells, exhibit unique focusing patterns compared to rigid particles. The outcomes, published in the Journal of Fluid Mechanics, pave the way for next-generation microfluidic devices leveraging cell and particle deformability, promising highly efficient cell sorting with biomedical applications such as early cancer detection.

Microfluidics involves manipulating fluids at a microscopic scale. Controlling particle movement within microchannels is crucial for cell sorting and diagnostics, expected to realize early cancer detection and treatment. While prior research focused on rigid particles, which typically focus near channel walls, the behavior of deformable particles remained largely unexplored. This study aimed to understand how particle deformability influences their focusing patterns. Researchers used specially designed hydrogel particles mimicking the size and softness of cells.

Combining experiments, simulations, and theoretical modeling, the team revealed stark differences in focusing behavior. Rigid particles migrate towards specific points near channel walls, while soft particles focus at the channel center or along the diagonals, depending on the flow conditions. Leveraging "Fugaku's" computational power, they simulated particle behavior under various flow regimes defined by the Reynolds number (inertia) and Capillary number (deformability). These simulations revealed a “phase transition” in the focusing pattern, governed by the ratio of these two numbers – the Laplace number. A new theoretical model explains this transition, offering fundamental insights into the underlying physics.

This research pioneers next-generation microfluidic technology by incorporating particle deformability as a critical design parameter, shifting microfluidic channel design from empirical towards a scientifically grounded approach. The new theoretical model dramatically streamlines design by decoupling the nonlinear problem into linear components of inertia and deformability. This enhanced control over cell sorting promises significant biomedical advancements, including improved early cancer detection by rapidly identifying cancer cells based on their distinct deformability compared to healthy cells, and monitoring treatment efficacy by assessing changes in cell stiffness. "We are committed to further developing this technology to realize its full potential in healthcare and biotechnology," affirmed Yuma Hirohata, the lead author of the study.

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The article, “Experimental and numerical study on the inertial migration of hydrogel particles suspended in square channel flows,” was published in Journal of Fluid Mechanics at DOI: https://doi.org/10.1017/jfm.2025.10574.