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DOI: 10.1088/1367-2630/13/3/035026
WoS: 000289066300007
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25 Citations
Résumé:

We study the sedimentation of buoyant giant lipid vesicles in a quiescent fluid at velocities ranging from 5 to 20 μm/s. Floppy vesicles are deformed by the flow. Their bottom (upstream) part remains spherical while their top (downstream) part narrows down and elongates along the direction of motion, resulting in pear-like shapes or in the reversible formation of a micron-size tube at the vesicle top. The sedimentation velocity of vesicle is very similar to that of a rigid sphere. Using a thermodynamic approach, we show that the hydrodynamic force acting at the top of a floppy vesicle can exceed the critical force needed to draw a membrane tube. We predict that the tube radius scales as the power 1/3 of the ratio of the bending energy to the typical hydrodynamic stress, ηU/R where η is the fluid viscosity, U is the sedimentation velocity and R the vesicle radius. This result is consistent with the reported experimental data. The tensions of vesicles exhibiting a tube and of pear-like shape are deduced from the thermodynamic approach

Commentaires: 16 pages