Paper Number
PO81
Session
Poster Session
Title
Elastic characterization of dense colloidal suspensions via droplet impact
Presentation Date and Time
October 12, 2022 (Wednesday) 6:30
Track / Room
Poster Session / Riverwalk A
Authors
- Seper, Brian C. (Northwestern University, Department of Physics and Astronomy)
- Shah, Phalguni (Northwestern University, Physics)
- Driscoll, Michelle M. (Northwestern University, Physics)
Author and Affiliation Lines
Brian C. Seper, Phalguni Shah and Michelle M. Driscoll
Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208
Speaker / Presenter
Seper, Brian C.
Keywords
colloids; jammed systems; suspensions
Text of Abstract
Colloidal suspensions display different flow properties depending on the concentration and the magnitude of the applied stress. When placed under large enough stresses at high concentrations, they display exotic behaviors such as shear thickening and shear jamming. Drop impact experiments allow for spatially resolved examinations of the material properties of complex fluids, in contrast to the bulk averaged measurements of conventional rheology. When impacting a surface, a suspension can experience a high enough instantaneous shear rate that the droplet can shear jam and completely solidify over the first few hundred microseconds after impact and re-fluidize over longer timescales, or the drop can rebound from the surface. We use high-speed high-resolution imaging to characterize the elastic modulus of dense colloidal suspensions (volume fractions between 0.48 and 0.51) by measuring the restitution coefficient and contact time of the drop when it bounces from a hydrophobic substrate after impact. We find that the restitution coefficient increases with increasing impact velocity, which implies that the material properties of the transient shear jammed state after impact are determined by the extent to which the impact conditions are beyond the onset of shear thickening.