Paper Number
GG47 

Session
Rheology of Gels, Glasses and Jammed Systems

Title
The hidden hierarchical nature of soft particulate gels

Presentation Date and Time
October 12, 2022 (Wednesday) 4:05

Track / Room
Track 3 / Sheraton 5

Authors (Click on name to view author profile)

  1. Keshavarz, Bavand (Massachusetts Institute of Technology, Mechanical Engineering)
  2. Bantawa, Minaspi (University of Texas at Austin, Department of Chemical Engineering)
  3. Geri, Michela (Massachusetts Institute of Technology, Department of Material Science and Engineering)
  4. Bouzid, Mehdi (Univ. Grenoble Alpes, CNRS)
  5. Divoux, Thibaut (ENSL, CNRS, Laboratoire de physique)
  6. McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)
  7. Del Gado, Emanuela (Georgetown University, Department of Physics)

Author and Affiliation Lines (in printed abstract book)
Bavand Keshavarz1, Minaspi Bantawa2, Michela Geri3, Mehdi Bouzid4, Thibaut Divoux5, Gareth H. McKinley1 and Emanuela Del Gado6
1Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; 2Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712; 3Department of Material Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02141; 4Univ. Grenoble Alpes, CNRS, Grenoble, France; 5ENSL, CNRS, Laboratoire de physique, Lyon, France; 6Department of Physics, Georgetown University, Washinton, DC 20057

Speaker / Presenter 
Keshavarz, Bavand

Keywords
theoretical methods; computational methods; colloids; gels; glasses

Text of Abstract
Soft particulate gels include materials we can eat, spread, squeeze, or 3D-print. From foods to bio-inks to cement hydrates, these gels are composed of a small amount of solid particulate matter (proteins, polymers, colloidal particles, or agglomerates of various origins) embedded in a continuous fluid phase. The solid component forms a porous percolated matrix, providing rigidity and control of the mechanical response, despite being the minority constituent. The lack of a unifying theoretical framework for particulate gels, together with the diverse range of materials involved, has so far challenged efforts to understand and predict the hierarchical rheological response and the range of elasticity in these viscoelastic soft solids. Using large-scale 3D microscopic simulations and windowed exponential chirp deformations we compute the viscoelastic signatures of gels for a wide range of particle volume fractions and gelation rates. We show that the linear rheology can be compactly represented in the form of a recursive mechanical ladder model, and use this insight to construct a universal master curve of the material response. A more detailed analysis of the underlying microscopic structure and dynamics reveals a hidden hierarchical organization of fractal elements that control the gel viscoelasticity and which is associated with the spatial heterogeneity of the solid matrix topology. These fractal elements provide the microscopic origin of the hierarchical rheological behavior and enable us to predict the scaling laws that capture the variations in viscoelasticity of these ubiquitous soft materials.