Noisy nonlinear dynamics of vesicles in flow

TL;DR

This paper introduces a comprehensive model for vesicle dynamics in flow that incorporates thermal fluctuations and nonlinear mode coupling, explaining experimental phenomena like trembling motion and asymmetric shapes.

Contribution

It provides the first model to include thermal noise and nonlinear effects in vesicle dynamics, predicting behaviors not captured by deterministic models.

Findings

Thermal fluctuations significantly amplify near the transition point.

Asymmetric vesicle shapes emerge despite deterministic symmetry constraints.

Model aligns quantitatively with recent experimental observations.

Abstract

We present a model for the dynamics of fluid vesicles in linear flow which consistently includes thermal fluctuations and nonlinear coupling between different modes. At the transition between tank-treading and tumbling, we predict a trembling motion which is at odds with the known deterministic motions and for which thermal noise is strongly amplified. In particular, highly asymmetric shapes are observed even though the deterministic flow only allows for axisymmetric ones. Our results explain quantitatively recent experimental observations [Levant and Steinberg, Phys. Rev. Lett. 109, 268103 (2012)].