Dynamics of Multicomponent Vesicles in Narrow Channel

We investigate the dynamics of two-dimensional multicomponent vesicles in confined Poiseuille flow, focusing on the interplay among membrane composition, mechanical heterogeneity, and hydrodynamic confinement. The membrane composition is described by a phase-field model, while the local bending rigidity depends on the phase composition, thereby coupling phase separation to membrane deformation. Local membrane inextensibility is imposed through a Lagrange multiplier, and the coupled vesicle-fluid system is solved using a boundary integral method for matched interior and exterior viscosities. At a fixed fivefold bending-rigidity contrast, we examine the effects of the average phase composition, channel width, and initial vesicle orientation. In contrast to homogeneous vesicles, which generally relax toward symmetric bullet-like configurations near the channel centerline, multicomponent vesicles exhibit pronounced symmetry breaking and a variety of dynamical states. These include asymmetric steady shapes accompanied by membrane tank-treading, as well as confinement-dependent breathing and wagging motions. Mechanical heterogeneity also promotes localized high-curvature regions during transient deformation, with softer membrane domains preferentially occupying regions of larger curvature. These results demonstrate that composition-dependent bending rigidity can qualitatively alter vesicle dynamics in pressure-driven confined flows and highlight the importance of membrane heterogeneity in the transport and deformation of vesicle-like cells in narrow channels.