The Society of Rheology 88th Annual Meeting

February 12-16, 2017 - Tampa, Florida


Biorheology & Active Fluids

Squeezing of vesicles through narrow tubes

February 13, 2017 (Monday) 3:35

Track 2 / Audubon A

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  1. Barakat, Joseph M. (Stanford University)
  2. Shaqfeh, Eric S. (Stanford University)

(in printed abstract book)
Joseph M. Barakat and Eric S. Shaqfeh
Stanford University, Stanford, CA 94305

Barakat, Joseph M.

Squeezing of vesicles through narrow constrictions increases membrane tension and enhances membrane permeability to molecular diffusants - e.g. pharmaceutical drugs - through the formation of transient pores. This process of "mechanoporation" shows promise for targeted drug delivery applications. The aim of the present work is to provide a theoretical model for vesicle squeezing that relates vesicular shape deformation in a highly confined, channel flow to the enhancement of hydrodynamic drag and membrane tension. The vesicle is modeled as an inextensible elastic sheet with a Helfrich bending stiffness and placed inside a circular tube of near-minimal diameter. Using a combination of semi-analytical theory and direct numerical simulation, the drag and tension are calculated as functions of the reduced volume, radius ratio, and bending capillary number. Significantly, corrections to "leading-order" calculations previously reported in the literature are reported here for the first time for vesicles. These findings show that the shape deformation near the vesicle "end-caps" lead to significant drag enhancement and strong variation in the membrane tension. As vesicles shorten in length, this end-cap effect changes quantitatively. Bending elasticity plays a comparatively weaker role relative to the effect of confinement. However, calculations performed at low bending capillary numbers reveal lobe-swelling and drag enhancement via occlusion of the small-gap flow. The theoretical results presented in this work show excellent agreement with prior and our present full numerical simulations performed for vesicles in confined flows as well as mobility measurements of confined red blood cells.