Paper Number
MF5
Session
Micro/Nano Fluidics and Probe Rheology
Title
Characterization of gelling suspensions by differential dynamic microscopy
Presentation Date and Time
February 14, 2017 (Tuesday) 5:15
Track / Room
Track 3 / White Ibis
Authors
- Shahsavari, Setareh (Massachusetts Institute of Technology)
- Caggioni, Marco (Procter and Gamble)
- Hartt, William H. (The Procter & Gamble Co)
- McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)
Author and Affiliation Lines
Setareh Shahsavari1, Marco Caggioni2, William H. Hartt2, and Gareth H. McKinley1
1Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; 2The Procter & Gamble Co, West Chester, OH 45040
Speaker / Presenter
Shahsavari, Setareh
Text of Abstract
In this work, we study the gelation dynamics of aqueous dispersions of silica nanoparticles. In the presence of salt, these colloidal dispersions form a reversible gel network at equilibrium and can be rejuvenated under shear deformation. We first, characterize the rheology of these materials on the macroscale. Through time-resolved bulk rheometry, we show that these systems are excellent model fluids for evaluation of thixotropic constitutive equations, as their thixotropic time scales can be tuned over a wide dynamic range by adjusting the ionic strength of the matrix fluid., We then use differential dynamic microscopy, which was originally developed by Cerbino and Trappe (2008) for investigating the Brownian dynamics of suspensions at equilibrium to investigate the miscrostructural characteristics of the gelling dispersions. We present the results in terms of the wave vector-dependent characteristic diffusive time scales as the dispersions progressively transitions from a liquid phase to a gel phase. We show that for these gelling fluids, unlike non-gelling suspensions at equilibrium, the dynamics of the aggregates can be dominated by advective motions rather than classical diffusive processes.