Dynamics of a viscous vesicle in linear flows
Petia M Vlahovska1, Ruben Serral Gracia
1Theory Department, Max-Planck Institute of Colloids and Interfaces, D-14424 Potsdam-Golm, Germany. petia.vlahovska@dartmouth.edu
Summary
This study presents a theory for lipid bilayer vesicle dynamics in fluid flow, predicting two behaviors: tank treading and tumbling, based on fluid viscosity. These findings offer insights into vesicle rheology and behavior in complex flows.
Area of Science:
- Biophysics
- Fluid Dynamics
- Materials Science
Background:
- Lipid bilayer membranes (vesicles) are fundamental to cell biology and biomaterials.
- Understanding vesicle dynamics in flow is crucial for biological processes and microfluidic applications.
- Existing models often simplify flow conditions or membrane properties.
Purpose of the Study:
- To develop an analytical theory for the dynamics of a single lipid bilayer vesicle in a general linear flow.
- To investigate the influence of membrane properties (fluidity, incompressibility, bending resistance) and fluid viscosity on vesicle behavior.
- To predict vesicle deformation, orientation, and potential non-Newtonian rheological effects.
Main Methods:
- Developed an analytical theory using creeping-flow equations and regular perturbation expansion for nearly spherical vesicles.
- Incorporated membrane properties: fluidity, incompressibility, and bending rigidity.
- Derived a nonlinear shape evolution equation based on fixed total area constraint.
Main Results:
- Predicted two distinct vesicle dynamics regimes: tank treading and tumbling, dependent on interior/exterior fluid viscosity contrast.
- Identified a critical viscosity contrast determining the transition between regimes.
- Tank treading regime shows orientation independent of bending rigidity; tumbling regime exhibits periodic shape changes with frequency dependent on viscosity contrast.
- Predicted non-Newtonian rheology, specifically normal stresses, for dilute vesicle suspensions.
Conclusions:
- The developed theory accurately describes vesicle dynamics in linear flow, including tank treading and tumbling regimes.
- The findings align well with experimental data for vesicle behavior in simple shear flow.
- The theory provides a framework for understanding vesicle rheology and predicting their response in various flow conditions.
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