Effects of shear rate and suspending medium viscosity on elongation of red cells tank-treading in shear flow

Abstract

Elongation measurements of red cells subjected to simple shear flow are usually performed using a single suspending medium (viscosity η 0) and varying the mean shear rate γ̇. Such data are often plotted versus the shear stress τ η 0γ̇ suggesting that the elongation scales with τ In this work, normal blood samples were tested in a rheoscope varying both η 0 and γ̇. The ranges of γ̇ were chosen to restrict the elongation of the red cells to low values where the behavior is dominated by their intrinsic properties. It was found that the elongation scales with η 0sγ̇ with s decreasing from two at η 0 = 20 mPas to unity at η 0 = 70 mPas. Above η 0 = 70 mPas, the elongation is therefore essentially determined by the membrane elasticity alone. A side observation was a large variation of the elongation both intraindividually and interindividually. © 2011 International Society for Advancement of Cytometry © 2011 International Society for Advancement of Cytometry.