Paper Number
BB13
Session
Biomaterials and Biofluid Dynamics
Title
Non-equilibrium dynamics of vesicles in flow using a Stokes trap
Presentation Date and Time
October 21, 2019 (Monday) 5:00
Track / Room
Track 6 / Room 306B
Authors
- Kumar, Dinesh (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
- Richter, Channing (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
- Schroeder, Charles M (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
Author and Affiliation Lines
Dinesh Kumar, Channing Richter, and Charles M Schroeder
Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801
Speaker / Presenter
Kumar, Dinesh
Text of Abstract
Vesicles are membrane-bound soft containers that play an integral role in key biological processes. In this work, we study the non-equilibrium dynamics of giant unilamellar vesicles in precisely-defined steady and time-dependent extensional flow. In particular, we use a Stokes trap to control the position and time-dependent strain and strain rate schedules applied to single vesicles in flow. In this way, we directly observe non-equilibrium vesicle shapes as a function of reduced volume, viscosity contrast, and Capillary number using fluorescence microscopy. Vesicles are found to deform through a wide-range of interesting shapes in flow, including asymmetric and symmetric dumbbells, in addition to pearling, wrinkling, and buckling instabilities depending on membrane properties. Using this approach, we precisely determine the flow phase diagram for vesicles in Capillary number-reduced volume space. We further study the non-equilibrium stretching dynamics of vesicles, including transient and steady-state stretching dynamics in extensional flow. Our results show that vesicle stretching dynamics are a strong function of reduced volume and viscosity ratio, such that the steady-state deformation of vesicles exhibits power-law behavior as a function of reduced Capillary number. We identify two distinct relaxation processes for vesicles stretched to high deformation, revealing two characteristic time scales: a short time scale corresponding to bending relaxation and a long-time scale dictated by the relaxation of membrane tension. We further discuss a method to estimate the bending modulus and intermonolayer friction of lipid membranes from the steady-state and relaxation data. Overall, our results provide new insights into the flow-driven shape-instabilities for vesicles using new experimental methods based on the Stokes trap.