Paper Number
PO120 

Session
Poster Session

Title
Non-equilibrium deformation and relaxation of giant floppy vesicles in a precisely controlled extensional flow

Presentation Date and Time
October 17, 2018 (Wednesday) 6:30

Track / Room
Poster Session / Woodway II/III

Authors (Click on name to view author profile)

1. Kumar, Dinesh (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
2. Schroeder, Charles M. (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Dinesh Kumar and Charles M. Schroeder
Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Speaker / Presenter 
Kumar, Dinesh

Text of Abstract
In this work, we study the non-equilibrium dynamics of single floppy vesicles under large strain rates (~15 s-1) using a Stokes trap, which is a new technique developed in our lab for controlling the center-of-mass position of multiple particles or single molecules in a free solution. In this way, we directly observe the vesicle shape and conformations as a function of reduced volume, which is a measure of a vesicle’s equilibrium shape departure from sphericity. We observe the formation of asymmetric dumbbell shapes, pearling, and wrinkling and buckling instabilities for vesicles depending upon the nature of flow and amount of membrane floppiness. We report the precise stability boundary of the flow-based phase diagram for vesicles in Capillary number (Ca)-reduced volume space, where Ca is the ratio of the bending time scale to the of flow time-scale. We further probe the stability boundary at two different viscosity ratios to understand how the onset of asymmetric instability in vesicles depends on viscosity ratio. We also present results on the long-time relaxation dynamics of vesicles from high deformation back to their equilibrium spheroidal shapes after the cessation of flow. We study vesicles with shapes ranging from symmetric to asymmetric dumbbells with a long thin tether (extremely large fractional extensions with flattened thermal fluctuations), and we report on the influence of initial conditions in determining dynamic behavior. Overall, our results provide new insights into the flow-driven shape-instabilities for vesicles which has been achieved using new experimental methods involving the Stokes trap and related precise control over the center-of-mass position of vesicles, resulting in observation times on order of the time required for instabilities to form.