Dynamics of fluid vesicles in flow through structured microchannels

¹  Institut für Festkörperforschung, Forschungszentrum Jülich - 52425 Jülich, Germany, EU
²  Institute for Solid State Physics, University of Tokyo - Kashiwa, Chiba 277-8581, Japan
³  Experimentalphysik I, Microfluidics Group, Universität Augsburg - 86159 Augsburg, Germany, EU

Corresponding authors: noguchi@issp.u-tokyo.ac.jp g.gompper@fz-juelich.de lothar.schmid@physik.uni-augsburg.de thomas.franke@physik.uni-augsburg.de

Received: 31 October 2009
Accepted: 11 January 2010

Abstract

The dynamics of fluid vesicles is studied under flow in microchannels, in which the width varies periodically along the channel. Three types of flow instabilities of prolate vesicles are found. For small quasi-spherical vesicles —compared to the average channel width— perturbation theory predicts a transition from a state with orientational oscillations of a fixed prolate shape to a state with shape oscillations of symmetrical ellipsoidal or bullet-like shapes with increasing flow velocity. Experimentally, such orientational oscillations are observed during the slow migration of a vesicle towards the centerline of the channel. For larger vesicles, mesoscale hydrodynamics simulations and experiments show similar symmetric shape oscillation at reduced volumes ≳ 0.9. However, for non-spherical vesicles with ≲ 0.9, shapes are found with two symmetric or a single asymmetric tail.