Membrane Viscosity Determined from Shear-Driven Flow in Giant Vesicles

TL;DR

This paper presents a novel microfluidic method to measure lipid bilayer membrane viscosity by analyzing shear-induced flow patterns inside adhered giant vesicles, combining experimental imaging and flow reconstruction.

Contribution

It introduces a new technique that accurately determines membrane viscosity through flow pattern analysis, validated against theoretical predictions.

Findings

Flow patterns match theoretical models.

Membrane viscosity can be directly measured.

Method enables detailed flow visualization inside vesicles.

Abstract

The viscosity of lipid bilayer membranes plays an important role in determining the diffusion constant of embedded proteins and the dynamics of membrane deformations, yet it has historically proven very difficult to measure. Here we introduce a new method based on quantification of the large-scale circulation patterns induced inside vesicles adhered to a solid surface and subjected to simple shear flow in a microfluidic device. Particle Image Velocimetry based on spinning disk confocal imaging of tracer particles inside and outside of the vesicle, and tracking of phase-separated membrane domains are used to reconstruct the full three-dimensional flow pattern induced by the shear. These measurements show excellent agreement with the predictions of a recent theoretical analysis, and allow direct determination of the membrane viscosity.