2013/05/31 by Neil Y. Lin, Xiang Cheng, Lin, Neil Y. +3
Physics and Astronomy · #FOS: Physical sciences #Soft Condensed Matter (cond-mat.soft) #cond-mat.soft
paper · pdf · doi:10.48550/arxiv.1305.7423
arxiv created 2013/05/31 · arxiv updated 2013/06/03
Using a novel bi-axial confocal rheoscope, we investigate the structure and rheology of sheared colloidal suspensions under confinement. Consistent with previous work [X. Cheng et al., Proc. Natl. Acad. Sci. U. S. A., 2011, 109, 63], we observe a vorticity-aligned string phase in moderate concentrated colloidal suspensions under uniaxial shear. Using bi-axial shear protocols, we directly manipulate the orientation and morphology of the string structures. Simultaneously, we measure the suspension rheology along both the flow and vorticity directions with a bi-axial force measurement device. Our results demonstrate that despite the highly anisotropic microstructure, the suspension viscosity remains isotropic and constant over the shear rates explored. These results suggest that hydrodynamic contributions dominate the suspension response. In addition they highlight the capabilities of bi-axial confocal rheoscopes for elucidating the relationship between microstructure and rheology in complex fluids.