How Confinement-Induced Structures Alter the Contribution of Hydrodynamic and Short-Ranged Repulsion Forces to the Viscosity of Colloidal Suspensions
Confined systems ranging from the atomic to the granular are ubiquitous in nature. Experiments and simulations of such atomic and granular systems have shown a complex relationship between the microstructural arrangements under confinement, the short-ranged particle stresses, and flow fields. Unders...
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| Format: | Article |
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American Physical Society (APS)
2018
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| Online Access: | http://hdl.handle.net/1721.1/114500 https://orcid.org/0000-0002-8254-2860 https://orcid.org/0000-0002-4244-8204 |
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| author | Ramaswamy, Meera Lin, Neil Y. C. Leahy, Brian D. Ness, Christopher Cohen, Itai Fiore, Andrew Michael Swan, James W |
| author2 | Massachusetts Institute of Technology. Department of Chemical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Chemical Engineering Ramaswamy, Meera Lin, Neil Y. C. Leahy, Brian D. Ness, Christopher Cohen, Itai Fiore, Andrew Michael Swan, James W |
| author_sort | Ramaswamy, Meera |
| collection | MIT |
| description | Confined systems ranging from the atomic to the granular are ubiquitous in nature. Experiments and simulations of such atomic and granular systems have shown a complex relationship between the microstructural arrangements under confinement, the short-ranged particle stresses, and flow fields. Understanding the same correlation between structure and rheology in the colloidal regime is important due to the significance of such suspensions in industrial applications. Moreover, colloidal suspensions exhibit a wide range of structures under confinement that could considerably modify such force balances and the resulting viscosity. Here, we use a combination of experiments and simulations to elucidate how confinement-induced structures alter the relative contributions of hydrodynamic and short-range repulsive forces to produce up to a tenfold change in the viscosity. In the experiments we use a custom-built confocal rheoscope to image the particle configurations of a colloidal suspension while simultaneously measuring its stress response. We find that as the gap decreases below 15 particle diameters, the viscosity first decreases from its bulk value, shows fluctuations with the gap, and then sharply increases for gaps below 3 particle diameters. These trends in the viscosity are shown to strongly correlate with the suspension microstructure. Further, we compare our experimental results to those from two different simulations techniques, which enables us to determine the relative contributions of hydrodynamic and short-range repulsive stresses to the suspension rheology. The first method uses the lubrication approximation to find the hydrodynamic stress and includes a short-range repulsive force between the particles while the second is a Stokesian dynamics simulation that calculates the full hydrodynamic stress in the suspension. We find that the decrease in the viscosity at moderate confinements has a significant contribution from both the hydrodynamic and shortrange repulsive forces whereas the increase in viscosities at gaps less than 3 particle diameters arises primarily from short-range repulsive forces. These results provide important insights into the rheological behavior of confined suspensions and further enable us to tune the viscosity of confined suspensions by changing properties such as the gap, polydispersity, and the volume fraction. Subject Areas: Fluid Dynamics, Soft Matter |
| first_indexed | 2024-09-23T10:20:15Z |
| format | Article |
| id | mit-1721.1/114500 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T10:20:15Z |
| publishDate | 2018 |
| publisher | American Physical Society (APS) |
| record_format | dspace |
| spelling | mit-1721.1/1145002022-09-30T20:31:06Z How Confinement-Induced Structures Alter the Contribution of Hydrodynamic and Short-Ranged Repulsion Forces to the Viscosity of Colloidal Suspensions Ramaswamy, Meera Lin, Neil Y. C. Leahy, Brian D. Ness, Christopher Cohen, Itai Fiore, Andrew Michael Swan, James W Massachusetts Institute of Technology. Department of Chemical Engineering Fiore, Andrew Michael Swan, James W Confined systems ranging from the atomic to the granular are ubiquitous in nature. Experiments and simulations of such atomic and granular systems have shown a complex relationship between the microstructural arrangements under confinement, the short-ranged particle stresses, and flow fields. Understanding the same correlation between structure and rheology in the colloidal regime is important due to the significance of such suspensions in industrial applications. Moreover, colloidal suspensions exhibit a wide range of structures under confinement that could considerably modify such force balances and the resulting viscosity. Here, we use a combination of experiments and simulations to elucidate how confinement-induced structures alter the relative contributions of hydrodynamic and short-range repulsive forces to produce up to a tenfold change in the viscosity. In the experiments we use a custom-built confocal rheoscope to image the particle configurations of a colloidal suspension while simultaneously measuring its stress response. We find that as the gap decreases below 15 particle diameters, the viscosity first decreases from its bulk value, shows fluctuations with the gap, and then sharply increases for gaps below 3 particle diameters. These trends in the viscosity are shown to strongly correlate with the suspension microstructure. Further, we compare our experimental results to those from two different simulations techniques, which enables us to determine the relative contributions of hydrodynamic and short-range repulsive stresses to the suspension rheology. The first method uses the lubrication approximation to find the hydrodynamic stress and includes a short-range repulsive force between the particles while the second is a Stokesian dynamics simulation that calculates the full hydrodynamic stress in the suspension. We find that the decrease in the viscosity at moderate confinements has a significant contribution from both the hydrodynamic and shortrange repulsive forces whereas the increase in viscosities at gaps less than 3 particle diameters arises primarily from short-range repulsive forces. These results provide important insights into the rheological behavior of confined suspensions and further enable us to tune the viscosity of confined suspensions by changing properties such as the gap, polydispersity, and the volume fraction. Subject Areas: Fluid Dynamics, Soft Matter MITEI-Shell Progam 2018-04-03T14:46:48Z 2018-04-03T14:46:48Z 2017-10 2017-06 2018-03-02T14:31:55Z Article http://purl.org/eprint/type/JournalArticle 2160-3308 http://hdl.handle.net/1721.1/114500 Ramaswamy, Meera, et al. “How Confinement-Induced Structures Alter the Contribution of Hydrodynamic and Short-Ranged Repulsion Forces to the Viscosity of Colloidal Suspensions.” Physical Review X, vol. 7, no. 4, Oct. 2017. © 2017 American Physical Society. https://orcid.org/0000-0002-8254-2860 https://orcid.org/0000-0002-4244-8204 http://dx.doi.org/10.1103/PHYSREVX.7.041005 Physical Review X Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/ application/pdf American Physical Society (APS) Physical Review X |
| spellingShingle | Ramaswamy, Meera Lin, Neil Y. C. Leahy, Brian D. Ness, Christopher Cohen, Itai Fiore, Andrew Michael Swan, James W How Confinement-Induced Structures Alter the Contribution of Hydrodynamic and Short-Ranged Repulsion Forces to the Viscosity of Colloidal Suspensions |
| title | How Confinement-Induced Structures Alter the Contribution of Hydrodynamic and Short-Ranged Repulsion Forces to the Viscosity of Colloidal Suspensions |
| title_full | How Confinement-Induced Structures Alter the Contribution of Hydrodynamic and Short-Ranged Repulsion Forces to the Viscosity of Colloidal Suspensions |
| title_fullStr | How Confinement-Induced Structures Alter the Contribution of Hydrodynamic and Short-Ranged Repulsion Forces to the Viscosity of Colloidal Suspensions |
| title_full_unstemmed | How Confinement-Induced Structures Alter the Contribution of Hydrodynamic and Short-Ranged Repulsion Forces to the Viscosity of Colloidal Suspensions |
| title_short | How Confinement-Induced Structures Alter the Contribution of Hydrodynamic and Short-Ranged Repulsion Forces to the Viscosity of Colloidal Suspensions |
| title_sort | how confinement induced structures alter the contribution of hydrodynamic and short ranged repulsion forces to the viscosity of colloidal suspensions |
| url | http://hdl.handle.net/1721.1/114500 https://orcid.org/0000-0002-8254-2860 https://orcid.org/0000-0002-4244-8204 |
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