L. Mountrakis, E. Lorenz, A.G. Hoekstra
Computational Science, University of Amsterdam, NL
The complex behavior of blood arises mainly from the high concentration of RBCs, which constitute up to 45 per cent of the total blood volume and many diseases are linked to the abnormal shape or mechanic response of the RBCs .
Red blood cells (RBCs) are highly deformable biconcave membranes, which enclose a Newtonian solution of hemoglobin. The membrane of an RBC is composed by a lipid bilayer, underlined by a molecular spectrin network and is found to exhibit shape memory [2, 3]. The membrane also experiences thermal fluctuations and fluctuations caused by metabolic activity related to ATP .
Under shear flow, RBCs exhibit two types of motion: (i) at lower shear rates RBCs flip like a rigid body (tumbling) and (ii) above a critical shear rate they assumes a shear-rate dependent inclination angle while their membrane undergoes a steady rotary motion (tank-treading). A swinging motion superimposed to tank-treading was observed experimentally, attributed mainly to the shape memory of an RBC .
In this study we investigate the connection of the shape memory and the membrane fluctuation with the transition from tumbling to tank-treading, which has recently been argued to be the major contributor to shear thinning . Lattice Boltzmann method is employed to resolve fluid flow, while RBCs are modeled on the spectrin level  coupled to the fluid with the immersed-boundary method.
 X. Li, P. M. Vlahovska, and G. E. Karniadakis, Soft Matter 9, 28 (2013).
 T. M. Fischer, Biophysical Journal 86, 3304 (2004).
 M. Abkarian, M. Faivre, and A. Viallat, Physical Review Letters 98, (2007).
 Y. Park et al, Proceedings of the National Academy of Sciences of the United States of America 107, 1289 (2010).
 A. M. Forsyth et al, Proceedings of the National Academy of Sciences of the United States of America 108, 10986 (2011).
 D. A. Fedosov, B. Caswell, and G. E. Karniadakis, Biophysical Journal 98, 2215 (2010).