Paper Number
GG35   Keynote 

Session
Rheology of Gels, Glasses and Jammed Systems

Title
Jamming distance dictates colloidal shear thickening

Presentation Date and Time
October 12, 2022 (Wednesday) 9:50

Track / Room
Track 3 / Sheraton 5

Authors (Click on name to view author profile)

  1. Hsiao, Lilian (North Carolina State University, Chemical and Biomolecular Engineering)
  2. Pradeep, Shravan (University of Pennsylvania, Earth and Environmental Sciences)

Author and Affiliation Lines (in printed abstract book)
Lilian Hsiao1 and Shravan Pradeep2
1Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27606; 2Earth and Environmental Sciences, University of Pennsylvania, Philadelphia, PA 19104

Speaker / Presenter 
Hsiao, Lilian

Keywords
experimental methods; colloids; jammed systems; suspensions

Text of Abstract
We report the steady state viscosity and contact microstructure of dense suspensions containing hard-particle poly(methyl methacrylate) (PMMA) colloids with tunable surface morphologies. Structural analysis of confocal micrographs shows that the contact number deficit ?z scales as the jamming distance ??, where the scaling relations contain a range of exponents that describe the compactability of frictional packings with jamming fractions ?J and jamming contact numbers zJ. Suspensions with rougher particles are more loosely packed than that of smoother particles near the jamming point. Agreement between model predictions from a mean-field theory and our rheological data shows that shear thickening is modeled by different types of frictional packings that form under applied shear stresses. The shear thickening strength, quantified by the slope of the viscosity-stress flow curves, scales with the jamming distance for a broad class of dense suspensions comprising PMMA smooth and rough colloids, silica smooth and rough colloids, and simulations with interparticle friction or surface asperities. Our results suggest that ??/?J = 0.1 and ?z/zJ = 0.5 is the point at which hydrodynamics, Brownian forces, and friction become equally important in colloidal shear thickening.