Swinging and tumbling of multicomponent vesicles in flow

TL;DR

This paper develops a reduced order model to study how heterogeneities in membrane properties affect vesicle dynamics in flow, revealing transitions from swinging to tumbling behaviors based on material variations.

Contribution

It introduces a novel reduced order model capturing the impact of spatially varying membrane properties on vesicle dynamics in flow.

Findings

Material variations induce transitions from swinging to tumbling behaviors.

Distinct dynamics are observed for even and odd domain distributions.

Numerical simulations validate the theoretical predictions even for large deformations.

Abstract

Biological membranes are host to proteins and molecules which may form domain-like structures resulting in spatially-varying material properties. Vesicles with such heterogeneous membranes can exhibit intricate shapes at equilibrium and rich dynamics when placed into a flow. Under the assumption of small deformations we develop a reduced order model to describe the fluid-structure interaction between a viscous background shear flow and an inextensible membrane in two dimensions with spatially varying bending stiffness and spontaneous curvature. Material property variations of a critical magnitude, relative to the flow rate and internal/external viscosity contrast, can set off a qualitative change in the vesicle dynamics. A membrane of nearly constant bending stiffness or spontaneous curvature undergoes a small amplitude swinging motion (which includes tangential tank-treading), while for large enough material variations the dynamics pass through a regime featuring tumbling and periodic phase-lagging of the membrane material, and ultimately for very large material variation to a rigid body tumbling behavior. Distinct differences are found for even and odd spatial modes of domain distribution. Full numerical simulations are used to probe the theoretical predictions, which appear valid even when studying substantially deformed membranes.