Paper Number
GG8 

Session
Out of Equilibrium Systems: Gels and Glasses

Title
Microscopic dynamics of stress relaxation in a nanocolloidal soft glass

Presentation Date and Time
October 21, 2019 (Monday) 2:20

Track / Room
Track 7 / Room 306C

Authors (Click on name to view author profile)

  1. Yihao, Chen (Johns Hopkins University)
  2. Rogers, Simon A. (University of Illinois at Urbana-Champaign, Department of Chemical and Biomolecular Engineering)
  3. Narayanan, Suresh (Argonne National Laboratory)
  4. Harden, James L. (University of Ottawa, Department of Physics)
  5. Leheny, Robert L. (Johns Hopkins University, Department of Physics and Astronomy)

Author and Affiliation Lines (in printed abstract book)
Chen Yihao1, Simon A. Rogers2, Suresh Narayanan3, James L. Harden4, and Robert L. Leheny1
1Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218; 2Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; 3Argonne National Laboratory, Lemont, IL 60439; 4Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada

Speaker / Presenter 
Yihao, Chen

Text of Abstract
Following the cessation of flow-inducing shear, soft disordered solids often display a protracted recovery during which the stress slowly decreases to a finite value known as the residual stress. While numerous rheology studies have characterized the macroscopic nature of this stress relaxation, little is known about the underlying microscopic structural dynamics. We report x-ray photon correlation spectroscopy (XPCS) experiments with in situ rheometry performed on a soft glass composed of a dense suspension of charged silica nanoparticles subject to step strains that induce yielding. The XPCS measurements characterize the particle-scale and mesoscale motions within the glass that underlie the subsequent slow decay of the stress. The XPCS correlation functions indicate these dynamics are anisotropic, with slow, convective-like particle motion along the direction of the preceding shear that persists for surprisingly large times after flow cessation and that is accompanied by highly intermittent motion in the perpendicular (vorticity) direction. The close correspondence between these dynamics and the stress relaxation is demonstrated by power-law scaling between the characteristic velocity of the convective motion and the rate of stress decay.