Paper Number
PG22 

Session
Polyelectrolytes, Self-assembling Systems & Gels

Title
Effect of confinement on the rheology of a yield-stress fluid

Presentation Date and Time
October 18, 2018 (Thursday) 8:40

Track / Room
Track 3 / Bellaire

Authors (Click on name to view author profile)

1. de Bruyn, John R. (University of Western Ontario, Physics and Astronomy)
2. Liu, Yang (University of Western Ontario, Physics and Astronomy)

Author and Affiliation Lines (in printed abstract book)
John R. de Bruyn and Yang Liu
Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7, Canada

Speaker / Presenter 
de Bruyn, John R.

Text of Abstract
We have studied the flow of Carbopol, a polymer microgel, confined to square microchannels with widths ranging from 451 μm down to 54 μm. Velocity profiles in the midplane of the channels were measured using particle image velocimetry. Carbopol is a yield-stress fluid, and the velocity profiles measured in the larger channels agreed well with simulations based on its measured bulk-scale rheology. In microchannels 150 μm or smaller in width, however, the velocity profiles could not be fitted by a model with a finite yield stress, but instead were well-described by a power-law model with zero yield stress. We explain the vanishing of the yield stress in terms of the confinement by the microchannels of structural elements in the Carbopol.