Membrane viscosity effects on the dynamics of vesicles

Lipid bilayers are the main structural component of cell membranes. The nanometrically thin bilayer behaves as a two-dimensional fluid and its shear viscosity controls the transport of embedded biomolecules and membrane deformations. In this study, we investigate the effect of membrane viscosity on dynamics of giant vesicles (closed membrane sacs). We show that membrane viscosity affects the thermally-driven shape fluctuations, especially the low-wavenumber modes. We develop a theoretical model based on the Seifert-Langer formulation and we apply it to analyze the time-correlations of the shape modes. The surface viscosity effect on the dynamic structure factor of membranes will also be discussed.