3 research outputs found
Vesicle dynamics in elongation flow: Wrinkling instability and bud formation
We present experimental results on the relaxation dynamics of vesicles
subjected to a time-dependent elongation flow. We observed and characterized a
new instability, which results in the formation of higher order modes of the
vesicle shape (wrinkles), after a switch in the direction of the gradient of
the velocity. This surprising generation of membrane wrinkles can be explained
by the appearance of a negative surface tension during the vesicle deflation,
due to compression in a sign-switching transient. Moreover, the formation of
buds in the vesicle membrane has been observed in the vicinity of the dynamical
transition point.Comment: 4 pages, 4 figure
Dynamics of Vesicles in shear and rotational flows: Modal Dynamics and Phase Diagram
Despite the recent upsurge of theoretical reduced models for vesicle shape
dynamics, comparisons with experiments have not been accomplished. We review
the implications of some of the recently proposed models for vesicle dynamics,
especially the Tumbling-Trembling domain regions of the phase plane and show
that they all fail to capture the essential behavior of real vesicles for
excess areas, \Delta, greater than 0.4. We emphasize new observations of shape
harmonics and the role of thermal fluctuations.Comment: (removed forgotten leftover figure files
Phase Diagram of Single Vesicle Dynamical States in Shear Flow
International audienceWe report the first experimental phase diagram of vesicle dynamical states in a shear flow presented in a space of two dimensionless parameters suggested recently by V. Lebedev et al. To reduce errors in the control parameters, 3D geometrical reconstruction and determination of the viscosity contrast of a vesicle in situ in a plane Couette flow device prior to the experiment are developed. Our results are in accord with the theory predicting three distinctly separating regions of vesicle dynamical states in the plane of just two self-similar parameters