Single vesicle dynamics in various flows: Experiment versus theory
by
Victor Steinberg(Department of Physics of Complex Systems, Weizmann Institute of Science, Israel)
→
Europe/Stockholm
Nordita Astrophysics Seminar Room
Nordita Astrophysics Seminar Room
Description
Dynamics of a single vesicle in shear, elongation, and general flows is investigated
experimentally. Phase diagram of three vesicle dynamical states is obtained
experimentally in both shear and general flows. The new control parameter, the ratio of
the vorticity to the strain rate ω/s, allows following an experimental path, which scans
across the whole phase diagram with a single vesicle. Surprisingly, all three states and
transitions between them are obtained on the same vesicle and at the same viscosity of
inner and outer fluids. We reveal the physical nature of the key dynamical state, coined
by us trembling, which shows up in intrinsic shape instability on each cycle resulted in
periodical bursting of higher order harmonics depending on the value of the control
parameter proportional to ω/s. The dynamics of trembling state is compared with
dynamics of a vesicle a time-dependent elongation flow, where the wrinkling instability
was discovered, and similar features are identified. Quantitative comparison with recently
proposed models and numerical simulations for vesicle dynamics is reviewed.
