Brown University School of Engineering

CFM/FTCP Seminar: Dynamics of Single Semi-flexible Polymers and Giant Vesicles in External Flows

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Tuesday, February 21, 2012 4:00pm - 5:00pm

Vasily Kantsler Goldstein Lab, DAMTP, University of Cambridge Dynamics of Single Semi-flexible Polymers and Giant Vesicles in External Flows Semi-flexible polymers (actin filaments) subject to hydrodynamic forcing play an important role in cytoskeletal dynamics in the cell. Giant vesicles are mimicking the cell membrane, therefore further helping to understand the rheological response of the cell. The non-equilibrium problem of vesicle and semi-flexible polymer dynamics is highly challenging due to the coupling between the objects deformations and the flow. This leads to a free-boundary hydrodynamic problem, where the object shape is not given a priori, but determined by interplay between flow, bending energy and the surface area and volume constraints in the case of the vesicles and the arc-length conservation in the case of the actin filaments. We have investigated experimentally dynamics of giant vesicles and actin filaments in different types of flow. Near hyperbolic stagnation points of the elongational flow filaments and vesicles experience a competition between bending elasticity and tension induced by the flow, and are predicted to display suppressed thermal fluctuations in the steady regime and a buckling instability under sudden change of the velocity gradient. Subject to a flow with vorticity, vesicles undergo tank-treading motion, trembling or tumbling, depending on the control parameters of the experiment. Host: