Paper Number
SC35 

Session
Suspensions, Colloids, and Granular Materials

Title
Using acoustic perturbations to dynamically tune shear thickening in colloidal suspensions

Presentation Date and Time
October 23, 2019 (Wednesday) 1:55

Track / Room
Track 2 / Room 304

Authors (Click on name to view author profile)

1. Sehgal, Prateek (Cornell University, Sibley School of Mechanical and Aerospace Engineering)
2. Ramaswamy, Meera (Cornell University, Applied Engineering and Physics)
3. Cohen, Itai (Cornell University, Applied Engineering and Physics)
4. Kirby, Brian J. (Cornell University, Sibley School of Mechanical and Aerospace Engineering)

Author and Affiliation Lines (in printed abstract book)
Prateek Sehgal¹, Meera Ramaswamy², Itai Cohen², and Brian J. Kirby^1
1Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853; ²Applied Engineering and Physics, Cornell University, Ithaca, NY 14850

Speaker / Presenter 
Sehgal, Prateek

Text of Abstract
Colloidal suspensions in industrial processes often exhibit shear thickening that is difficult to control actively without changing the physical properties of the suspension constituents. In this work, we present a novel method in which we use acoustic perturbations to actively tune the shear thickening in these suspensions and investigate their dynamics. The key principle underlying our work is that nanoscale acoustic disturbances locally perturb particles and break the force chains responsible for thickening, and thus reduce the suspension viscosity. We apply acoustic perturbations by bonding a piezoelectric element to the bottom plate of the rheometer. We find that the suspension viscosity can be tunably reduced by simply varying the perturbation amplitude, and this tunable dethickening is achieved only at the shear rates corresponding to a thickened state. Additionally, we investigate the suspension dynamics and the temporal evolution of the force chains governing the viscosity using our customized acoustic-rheometer setup. We precisely measure the hysteretic rheological response by cyclically varying the input power. Importantly, this methodology of applying time varying acoustic perturbations can be generally applied in many other soft material systems ranging from polymers and bio-gels to granular materials and emulsions to probe various timescales in play and elucidate mechanisms governing the rheology. The ease with which this technique is applied makes it a powerful method for actively controlling suspension flow properties and investigating system dynamics.