Breakage of vesicles in a simple shear flow

Area of Science:

• Biophysics
• Materials Science
• Fluid Dynamics

Background:

• Micron-size lipid vesicles are model systems for cell membranes.
• Understanding vesicle stability in flow is crucial for biological and industrial applications.

Purpose of the Study:

• To investigate the mechanism and kinetics of lipid vesicle breakage in simple shear flow.
• To determine the critical parameters influencing vesicle fragmentation.

Main Methods:

• Studied 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DOPC) lipid vesicles in aqueous suspension.
• Applied controlled shear rates (1000–4000 s⁻¹) using a shear cell.
• Monitored vesicle size distribution and morphology over time using optical microscopy.

Main Results:

• Vesicle diameter decreased with time, with a 38% reduction at 4000 s⁻¹ after 6 hours.
• A critical diameter was observed, with larger vesicles decreasing and smaller ones increasing.
• Vesicle aspect ratio increased due to fluid leakage, leading to elongation and pearling instability.
• Low capillary numbers indicated breakage did not involve membrane lysis.

Conclusions:

• Simple shear flow induces lipid vesicle fragmentation through a pearling mechanism.
• Vesicle rupture is governed by fluid leakage and membrane deformation, not lysis.
• The findings provide insights into the mechanical stability of lipid vesicles under flow conditions.