ESPCI web site
Blood : flow, swimming and patterns
Blood elements (like red blood cells=RBC) can either be transported by a flow or they can behave as active machines –amoeboid swimmers– (the case of leukocytes). In the first part, several rich dynamics and patterns of RBCs under flow will be described, such as "blood crystals" (spontaneous order of RBCs under pure hydrodynamic interactions), similarities with traffic flow, or the existence of an optimal hematocrit. Flow in complex architectures (networks) of healthy and pathological cells (like sickle cell anemia) will be briefly presented.
The second part of the talk will be devoted to amoeboid swimming. The swimmer displays a rich behavior : it may settle into a straight trajectory in the channel or navigate from one wall to the other depending on its confinement. The swimmer is also shown to undergo a symmetry-breaking bifurcation where it moves out-of the central axis. The nature of the swimmer is affected by confinement : the swimmer can behave, on the average over one swimming cycle, as a pusher at low confinement, and becomes a puller at higher confinement, or vice versa. It is shown that the swimming velocity is a nonlinear function of the local force (the total force is zero) even in the pure Stokes regime.