Quantitative prediction of elongation deformation and shape relaxation of a red blood cell under tensile and shear stresses

CB Wu and S Wang and XJ Qi and WW Yan and XJ Li, PHYSICS OF FLUIDS, 33, 111906 (2021).

DOI: 10.1063/5.0071441

The characteristic time of stress relaxation is a key viscoelastic property of cell membrane that controls time-dependent processes such as shape recovery. Although many experimental studies have been devoted to the measurement of characteristic relaxation time, considerable uncertainty still stands because existing methods rely on different experimental designs and analyses. Here, we present a mesoscopic computational study to investigate the elastic deformation and relaxation characteristics of an isolated red blood cell (RBC) under both tensile and shear stresses. We examine the elastic response and relaxation behavior of the RBC under static tensile stretching and dynamic shear stress. When the cell deformation index responding fluid shear stress is equivalent to the one responding external tensile stretching, we find that the characteristic relaxation time for the RBC in planar flows is longer than that for the RBC under tensile stretching. We also subject the RBC to confined tube/channel flows to probe the effect of geometric confinement on its elastic deformation and relaxation dynamics. Our simulations show that the computed characteristic relaxation time is further increased when compared to those obtained under tensile stretching or planar flows, indicating that the confinement would slow down the cell relaxation process, especially under strong confinement conditions. These findings may facilitate a better understanding of variable relaxation time observed in different experiments.

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