TETHERING AND PEARLING OF A SETTLING VESICLE
Gwenn Boedec (IRPHE), Marc Jaeger (M2P2), Marc Leonetti (IRPHE)
Computational Mechanics of Biomembranes
Mon 10:45 - 12:15
Barus-Holley 160
Vesicles are micrometric drops enclosed by a phospholipidic membrane, which gives the interface peculiar properties : deformations are governed by surface incompressibility and bending resistance instead of the classic surface tension. Studies of vesicle behavior under hydrodynamical stresses have known a growing interest, not only because of their relevance for biological problematics like blood rheology, but also from the physics point of view : despite the linearity of Stokes equation, interplay of interface mechanics and flow leads to complex non linear behavior. Yet, little is known on the large deformation regime which can be encountered either when the forcing is large or when the vesicle is highly deflated. The typical response of a vesicle in such situations is the formation of a thin membrane tube (tether), connected to the mother vesicle. This is reminiscient of the formation of filament on pendant drops, but while these filaments are usually associated with breakup for newtonian drops, the specific properties of the vesicle interface permit to stabilize the filament. We study the formation of such hydrodynamically induced tethers in the case of a settling vesicle. In this situation, a stationnary shape composed of one mother and one daughter vesicle connected by a tether is reached. The stabilization of the deformation is tracked back to the membrane properties. Tether characteristics can be tuned either by the hydrodynamical forcing (Bond number) or by the deformability (excess area). Contrary to the case of point-like force, there is no discontinuity, as there exist continuous families of shapes which connects quasi-spherical pear-like shapes to tethers. Dynamics of formation is studied and it is shown that changing the initial condition can lead to complex transients, with formation of pearls onto the tether.