How red blood cells behave in tiny tubes

The behavior of red blood cells in microchannels, such as capillaries, has not been systematically studied under different conditions. With numerical analysis, Wang et al. investigated how certain factors, such as tube diameter, membrane shear modulus, initial position, and viscosity ratio, affect the phase diagrams of red blood cells in microchannels.

The authors constructed phase diagrams of red blood cell equilibrium states over a wide range of capillary numbers. These equilibrium states, including snaking, tumbling, slipper, and parachute, describe a cell’s motion and deformation under flow. They found that beyond a critical capillary number, red blood cells have two stable equilibrium states, slipper or parachute, depending on their initial position. This critical capillary number increases as microchannel diameter decreases.

Because the behavior of red blood cells influences blood flow, these results can be used to understand the mechanisms of mass transfer in microcirculation. This work showed that mass transfer may favor the slipper equilibrium state, as this state is associated with smaller membrane tension and faster velocity.

“Our findings provide new insights into the behavior of erythrocytes in microchannels and advance our understanding of fluid-membrane interactions in hemodynamics,” said author Xiaobo Gong. “They have important implications for investigating the hemodynamic mechanisms of physiological and pathological conditions at the cellular scale, such as in microcirculatory disorders.”

Next, the authors will explore other factors that affect red blood cell behavior, such as external forces and the presence of other types of cells. They also plan to apply these results to the design of microfluidic devices, including organs-on-chips and tools used to measure mechanical properties of cells.

Source: “Effect of mechanical properties of red blood cells on their equilibrium states in microchannels,” by Xiaolong Wang, Satoshi Ii, Kazuyasu Sugiyama, Shigeho Noda, Peng Jing, Deyun Liu, XiaJing, and Xiaobo Gong, Physics of Fluids (2023). The article can be accessed at https://doi.org/10.1063/5.0141811 .