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Hydrodynamics of Membranes and Vesicles

Stephen A. Langer, ACMD
Udo Seifert, IFF Jülich, Germany
Michael Wortis, Simon Fraser University

Phospholipid membranes are one of the key components of biological cells. A vesicle is a closed, topologically spherical piece of membrane. Artificial vesicles made in the laboratory exhibit a wide range of shapes, transitions, and fluctuations, as well as mimicking some biological phenomena. They are beginning to be used in biomedical applications. A description of the motion of a vesicle must include the three dimensional flow of the surrounding water, the deformation of the membrane, and the two dimensional flow of the lipids over the surface of the membrane, while conserving the volume of water enclosed in the vesicle and the total area of the membrane. Even in the simplest case (axisymmetric vesicles and small Reynolds number hydrodynamics) the resulting integro-differential equations form a formidable numerical challenge. In other words, none of the approaches tried so far have successfully computed the time evolution of the shape of a non-equilibrium vesicle.