Non-equilibrium dynamics of initially spherical vesicles in general flow

Abstract

Many vesicles have a spherical resting shape and exposure to fluid flows induces an exchange between sub-optical fluctuations and visible (systematic) deformation, while the total area is conserved. These dynamics can be used to determine membrane properties such as the resting surface tension and the membrane bending rigidity. In this work a general numerical model is extended to account for the exchange between sub-optical fluctuations and visible area. Compared to many prior methods, assumptions about the underlying flow field or vesicle shape are not made. It is thus possible to model a wide number of experimental conditions. The methods shown here are compared against several published experimental results and show excellent agreement. It is then used to explore how system properties, such as the viscosity ratio between the inner and outer fluid, influence experimentally measurable parameters. Such information is critical when designing experiments to extract membrane properties.