title: Membrane viscosity determined from shear-driven flow in giant 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.
authors.affiliation: Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom.
authors.forename: Aurelia R
authors.initials: AR
authors.lastname: Honerkamp-Smith
authors.forename: Francis G
authors.initials: FG
authors.lastname: Woodhouse
authors.forename: Vasily
authors.initials: V
authors.lastname: Kantsler
authors.forename: Raymond E
authors.initials: RE
authors.lastname: Goldstein
mesh_terms: D044784:Chara / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D008566:Membranes / Q000737:chemistry* / Q000378:metabolism; D046210:Microfluidic Analytical Techniques; D008954:Models, Biological; D008956:Models, Chemical; D014617:Vacuoles / Q000737:chemistry* / Q000378:metabolism; D014783:Viscosity