A red blood cell (RBC) is composed of an inner viscous fluid and its encapsulating outer viscoelastic cell membrane. In this study, computer modeling and simulation were conducted to understand characteristic deformation and motion exhibited by RBCs in blood. Simulation results demonstrated the importance of the natural state of the cell membrane; given measured elastic constants, the non-spherical natural state is necessary to maintain the biconcave disc shape exhibited by a normal RBC [1]. The natural state also determines the mode of rotational motion of the RBC in response to shear flow strength via rotational elasticity. By using the elongational deformation of the RBC, the strain-hardening properties of the cell membrane elasticity at large deformation regime can be successfully expressed by modifying the constitutive law of Skalak et al. with Fung’s exponential form [2]. These mechanical properties of individual red blood cells play an important role in determining the distribution of blood cells in the tubular cross section [3], which may influence blood flow in the vascular network [4,5] and thrombus formation [6].

This study was partly funded by a Grant-in-Aid for Scientific Research (20K04281, 23H01337), JSPS.