Paper Number
GG15 

Session
Arrested Systems: Gels and Glasses

Title
Hierarchical nature of linear viscoelastic response in colloidal gels

Presentation Date and Time
October 12, 2021 (Tuesday) 1:30

Track / Room
Track 6 / Ballroom 1

Authors (Click on name to view author profile)

  1. Bantawa, Minaspi (Georgetown University, Department of Physics)
  2. Keshavarz, Bavand (Massachusetts Institute of Technology)
  3. Geri, Michela (Massachusetts Institute of Technology)
  4. Bouzid, Mehdi (University of Grenoble, CNRS)
  5. Divoux, Thibaut (ENS Lyon, CNRS)
  6. Del Gado, Emanuela (Georgetown University)
  7. McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Minaspi Bantawa1, Bavand Keshavarz2, Michela Geri2, Mehdi Bouzid3, Thibaut Divoux4, Emanuela Del Gado1 and Gareth H. McKinley2
1Department of Physics, Georgetown University, Washington, DC 20057-0004; 2Massachusetts Institute of Technology, Cambridge, MA; 3CNRS, University of Grenoble, GRENOBLE, France; 4CNRS, ENS Lyon, Lyon, France

Speaker / Presenter 
Del Gado, Emanuela

Keywords
theoretical methods; computational methods; colloids; gels; non-Newtonian fluids; rheology methods

Text of Abstract
Colloidal gels are materials in which a relatively small amount of solid material (colloidal particles or small aggregates) is embedded in a fluid. The solid component is spatially organized into an open, porous network and, in spite of being the minority constituent, is able to provide rigidity and control the mechanical response of the whole material. In many practical applications, these gels are marginally rigid and measuring their response is hard both in simulations and experiments, because they are extremely soft and viscoelastic. We have used large scale simulations with a 3D numerical model and Optimally Windowed Chirp (OWCh) signals to investigate the microscopic origin of the viscoelastic response of soft particulate gels. The main ingredients of the model are short-ranged attractive interactions and bending stiffness for the inter-particle bonds. Using the OWCh protocol we have analyzed the key features of the frequency-dependent dynamic modulus G*(\omega) and their dependence on the gel connectivity and on the preparation protocol. Our analysis indicates that the viscoelastic spectrum of a wide range of gels, with different microstructures, is controlled by an underlying fractal characteristic of the gel network, i.e., its initial rigid backbone, and by the associated hierarchy of time scales. We discuss the microscopic structural and dynamical origin of these hierarchical processes and the emerging scaling behaviors.