1
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Kim H, van der Naald M, Dolinski ND, Rowan SJ, Jaeger HM. Dynamic-bond-induced sticky friction tailors non-Newtonian rheology. SOFT MATTER 2023; 19:6797-6804. [PMID: 37646285 DOI: 10.1039/d3sm00479a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Frictional network formation has become a new paradigm for understanding the non-Newtonian shear-thickening behavior of dense suspensions. Recent studies have exclusively focused on interparticle friction that instantaneously vanishes when applied shear is ceased. Herein, we investigate a friction that emerges from dynamic chemical bridging of functionalized particle surfaces sheared into close proximity. This enables tailoring of both friction magnitude and the time release of the frictional coupling. The experiments use dense suspensions of thiol-functionalized particles suspended in ditopic polymers endcapped with benzalcyanoacetamide Michael-acceptors. The subsequent room temperature, catalyst-free dynamic thia-Michael reactions can form bridging interactions between the particles with dynamic covalent bonds that linger after formation and release in the absence of shear. This chemical friction mimics physical friction but is stickier, leading to tunable rheopexy. The effect of sticky friction on dense suspension rheology is explored by varying the electronic nature of the benzalcyanoacetamide moiety, the molecular weight of the ditopic polymers, the amount of a competitive bonding compound, and temperature. These results demonstrate how dynamic-bond-induced sticky friction can be used to systematically control the time dependence of the non-Newtonian suspension rheology.
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Affiliation(s)
- Hojin Kim
- James Franck Institute and Department of Physics, The University of Chicago, Chicago, Illinois 60637, USA.
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA.
| | - Mike van der Naald
- James Franck Institute and Department of Physics, The University of Chicago, Chicago, Illinois 60637, USA.
| | - Neil D Dolinski
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA.
| | - Stuart J Rowan
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA.
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA
| | - Heinrich M Jaeger
- James Franck Institute and Department of Physics, The University of Chicago, Chicago, Illinois 60637, USA.
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2
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Singh A, Saitoh K. Scaling relationships between viscosity and diffusivity in shear-thickening suspensions. SOFT MATTER 2023; 19:6631-6640. [PMID: 37599580 DOI: 10.1039/d3sm00510k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/22/2023]
Abstract
Dense suspensions often exhibit a dramatic response to large external deformation. The recent body of work has related this behavior to transition from an unconstrained lubricated state to a constrained frictional state. Here, we use numerical simulations to study the flow behavior and shear-induced diffusion of frictional non-Brownian spheres in two dimensions under simple shear flow. We first show that both viscosity η and diffusivity D/ of the particles increase under characteristic shear stress, which is associated with lubrication to frictional transition. Subsequently, we propose a one-to-one relationship between viscosity and diffusivity using the length scale ξ associated with the size of collective motions (rigid clusters) of the particles. We demonstrate that η and D/ are controlled by ξ in two distinct flow regimes, i.e. in the frictionless and frictional states, where the one-to-one relationship is described as a crossover from D/ ∼ η (frictionless) to η1/3 (frictional). We also confirm that the proposed power laws are insensitive to the interparticle friction and system size.
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Affiliation(s)
- Abhinendra Singh
- Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106, USA.
| | - Kuniyasu Saitoh
- Department of Physics, Faculty of Science, Kyoto Sangyo University, Kyoto 603-8555, Japan.
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3
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Corder RD, Chen YJ, Pibulchinda P, Youngblood JP, Ardekani AM, Erk KA. Rheology of 3D printable ceramic suspensions: effects of non-adsorbing polymer on discontinuous shear thickening. SOFT MATTER 2023; 19:882-891. [PMID: 36645088 DOI: 10.1039/d2sm01396g] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Concentrated suspensions of particles at volume fractions (ϕ) ≥ 0.5 often exhibit complex rheological behavior, transitioning from shear thinning to shear thickening as the shear stress or shear rate is increased. These suspensions can be extruded to form 3D structures, with non-adsorbing polymers often added as rheology modifiers to improve printability. Understanding how non-adsorbing polymers affect the suspension rheology, particularly the onset of shear thickening, is critical to the design of particle inks that will extrude uniformly. In this work, we examine the rheology of concentrated aqueous suspensions of colloidal alumina particles and the effects of adding non-adsorbing polyvinylpyrrolidone (PVP). First, we show that suspensions with ϕalumina = 0.560-0.575 exhibited discontinuous shear thickening (DST), where the viscosity increased by up to two orders of magnitude above an onset stress (τmin). Increasing ϕalumina from 0.550 to 0.575 increased the viscosity and yield stress in the shear thinning regime and decreased τmin. Next, PVP was added at concentrations within the dilute and semi-dilute non-entangled regimes of polymer conformation (ϕPVP = 0.005-0.050) to suspensions with constant ϕalumina = 0.550. DST was observed in all cases and increasing ϕPVP increased the viscosity and yield stress. Interestingly, increasing ϕPVP also increased τmin. We posit that the free PVP chains act as lubricants between alumina particles, increasing the stress needed to induce thickening. Finally, we demonstrate through direct comparisons of suspensions with and without PVP how non-adsorbing polymer addition can extend the extrusion processing window due to the increase in τmin.
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Affiliation(s)
- Ria D Corder
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Yuan-Jung Chen
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
| | - Pattiya Pibulchinda
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
| | - Jeffrey P Youngblood
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
| | - Arezoo M Ardekani
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - Kendra A Erk
- School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
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4
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In Situ Observation of Shear-Induced Jamming Front Propagation during Low-Velocity Impact in Polypropylene Glycol/Fumed Silica Shear Thickening Fluids. Polymers (Basel) 2022; 14:polym14142768. [PMID: 35890543 PMCID: PMC9322945 DOI: 10.3390/polym14142768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 06/29/2022] [Accepted: 07/05/2022] [Indexed: 11/17/2022] Open
Abstract
Shear jamming, a relatively new type of phase transition from discontinuous shear thickening into a solid-like state driven by shear in dense suspensions, has been shown to originate from frictional interactions between particles. However, not all dense suspensions shear jam. Dense fumed silica colloidal systems have wide applications in the industry of smart materials from body armor to dynamic dampers due to extremely low bulk density and high colloid stability. In this paper, we provide new evidence of shear jamming in polypropylene glycol/fumed silica suspensions using optical in situ speed recording during low-velocity impact and explain how it contributes to impact absorption. Flow rheology confirmed the presence of discontinuous shear thickening at all studied concentrations. Calculations of the flow during impact reveal that front propagation speed is 3–5 times higher than the speed of the impactor rod, which rules out jamming by densification, showing that the cause of the drastic impact absorption is the shear jamming. The main impact absorption begins when the jamming front reaches the boundary, creating a solid-like plug under the rod that confronts its movement. These results provide important insights into the impact absorption mechanism in fumed silica suspensions with a focus on shear jamming.
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Zhou X, Yang J, Yin JF, Liu-Fu W, Huang J, Li M, Liu Y, Cai L, Sun TL, Yin P. Dimerization of sub-nanoscale molecular clusters affords broadly tuneable viscoelasticity above the glass transition temperature. Chem Sci 2022; 13:11633-11638. [PMID: 36320389 PMCID: PMC9557216 DOI: 10.1039/d2sc03651g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 09/19/2022] [Indexed: 11/21/2022] Open
Abstract
Materials with promising mechanical performance generally demonstrate requirements for the critical sizes of their key building units, e.g. entanglements and crystal grains. Herein, only with van der Waals interaction, viscoelasticity with broad tunability has been facilely achieved below the critical size limits: the dimers of ∼1 nm polyhedral oligomeric silsesquioxane (POSS) with Mw < 4 kD and size < 5 nm, which demonstrate distinct material physics compared to that of polymer nanocomposites of POSS. The dimeric POSSs are confirmed by scattering and calorimetrical measurements to be intrinsic glassy materials with glass transition temperatures (Tgs) lower than room temperature. From rheological studies, their viscoelasticity can be broadly tuned through the simple tailoring of the dimer linker structures above their Tg. In dimer bulks, each POSS cluster is spatially confined by the POSSs from other dimers and therefore, the correlation of the dynamics of the two linked POSS clusters, which, as indicated by dynamics analysis, is regulated by the length and flexibilities of linkers, contributes to the caging dynamics of POSS confined by their neighbours and the resulting unique viscoelasticity. Our discoveries update the understanding of the structural origin of viscoelasticity and open avenues to fabricate structural materials from the design of sub-nanoscale building blocks. The critical size limit for general structural material design is challenged in the dimers of sub-nm molecular clusters that possess small sizes (<5 nm) and broadly tunable viscoelasticity.![]()
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Affiliation(s)
- Xin Zhou
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510640, China
| | - Junsheng Yang
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510640, China
| | - Jia-Fu Yin
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510640, China
| | - Wei Liu-Fu
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510640, China
| | - Jiayi Huang
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510640, China
| | - Mu Li
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510640, China
| | - Yuan Liu
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510640, China
| | - Linkun Cai
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510640, China
| | - Tao Lin Sun
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510640, China
| | - Panchao Yin
- State Key Laboratory of Luminescent Materials and Devices & South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510640, China
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6
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Zhang X, Dai X, Han Q, Zhao J, Jing D, Liu F, Li L, Xin Y, Liu K. Prediction and New Insight for the Drag Reduction of Turbulent Flow with Polymers and Its Degradation Mechanism. J Phys Chem Lett 2021; 12:7201-7206. [PMID: 34310148 DOI: 10.1021/acs.jpclett.1c02027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A physicochemical understanding of the mechanism of turbulent flow drag reduction with polymer and its degradation is of great interest from both science and industry perspectives. Although the correlation based on the Fourier series has been proposed to predict the drag reduction and its degradation, its physical meaning was not clear until now. This letter aims to clarify this issue. We develop a comprehensive model to predict the drag reduction and degradation of polymers in turbulent flow from a chemical thermodynamics and kinetics viewpoint. We demonstrate that the Fourier series employed to predict the drag reduction and its degradation is due to the viscoelastic property of drag-reducing polymer solution, and the phase angle in the model, in physical nature, represents the hysteresis of the polymer in turbulent flow. Besides, our new insight of drag reduction with flexible polymers can also explain why a maximum drag reduction in rotational flow appears before degradation happens.
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Affiliation(s)
- Xin Zhang
- College of Petroleum Engineering, Shandong Institute of Petroleum and Chemical Technology, Dongying, Shandong 257061, People's Republic of China
| | - Xiaodong Dai
- College of Petroleum Engineering, Shandong Institute of Petroleum and Chemical Technology, Dongying, Shandong 257061, People's Republic of China
| | - Qiaorong Han
- Oil & Gas Technology Research Institute of Changqing Oilfield Company, Xi'an, Shaanxi 710018, People's Republic of China
| | - Jishi Zhao
- Yunfu (Foshan) R&D Center of Hydrogen Energy Standardization, Yunfu, Guangdong 527326, People's Republic of China
| | - Dengwei Jing
- State Key Laboratory of Multiphase Flow in Power Engineering & International Research Center for Renewable Energy, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, People's Republic of China
| | - Fei Liu
- College of Petroleum Engineering, Shandong Institute of Petroleum and Chemical Technology, Dongying, Shandong 257061, People's Republic of China
| | - Lei Li
- College of Petroleum Engineering, Shandong Institute of Petroleum and Chemical Technology, Dongying, Shandong 257061, People's Republic of China
| | - Yanping Xin
- College of Petroleum Engineering, Shandong Institute of Petroleum and Chemical Technology, Dongying, Shandong 257061, People's Republic of China
| | - Kun Liu
- College of Petroleum Engineering, Shandong Institute of Petroleum and Chemical Technology, Dongying, Shandong 257061, People's Republic of China
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7
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Arshad M, Maali A, Claudet C, Lobry L, Peters F, Lemaire E. An experimental study on the role of inter-particle friction in the shear-thinning behavior of non-Brownian suspensions. SOFT MATTER 2021; 17:6088-6097. [PMID: 34124737 DOI: 10.1039/d1sm00254f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
This paper focuses on shear-thinning in non-Brownian suspensions. In particular, it proposes a quantitative experimental validation of the model proposed by Lobry et al. [J. Fluid Mech., 2019, 860, 682-710] that links viscosity to microscopic friction between particles and, in particular, shear-thinning to load-dependent friction coefficient. To this aim, Atomic Force Microscopy (AFM) is used to measure the pairwise friction coefficient of polystyrene particles (40 μm in diameter), immersed in a Newtonian liquid, for different normal loads ranging from 10 to 1000 nN. It is shown that the inter-particle friction coefficient decreases with the load, contrarily to what is expected for macroscopic contacting bodies. The experimental friction law is then introduced into the viscosity model proposed by Lobry et al. and the results are compared to the viscosity of suspensions made of the same particles dispersed in the same liquid as those used for AFM measurements. The very good agreement between the measured viscosity values and those predicted by the model of Lobry et al. with the friction coefficient measured by AFM as input data shows the relevance of the scenario proposed by Lobry et al. and highlights the close links between the microscopic friction properties of the particles and the macroscopic rheological behavior of suspensions.
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Affiliation(s)
- Muhammad Arshad
- Laboratoire Onde et Matière d'Aquitaine, UMR 5798 CNRS-Université Bordeaux, 33405 Talence cedex, France
| | - Abdelhamid Maali
- Laboratoire Onde et Matière d'Aquitaine, UMR 5798 CNRS-Université Bordeaux, 33405 Talence cedex, France
| | - Cyrille Claudet
- Institut de Physique de Nice, UMR 7010 CNRS-Université Côte d'Azur, 06108 Nice cedex 2, France.
| | - Laurent Lobry
- Institut de Physique de Nice, UMR 7010 CNRS-Université Côte d'Azur, 06108 Nice cedex 2, France.
| | - Francois Peters
- Institut de Physique de Nice, UMR 7010 CNRS-Université Côte d'Azur, 06108 Nice cedex 2, France.
| | - Elisabeth Lemaire
- Institut de Physique de Nice, UMR 7010 CNRS-Université Côte d'Azur, 06108 Nice cedex 2, France.
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8
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van der Naald M, Zhao L, Jackson GL, Jaeger HM. The role of solvent molecular weight in shear thickening and shear jamming. SOFT MATTER 2021; 17:3144-3152. [PMID: 33600547 DOI: 10.1039/d0sm01350a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The application of stress can drive a dense suspension into a regime of highly non-Newtonian response, characterized by discontinuous shear thickening (DST) and potentially shear jamming (SJ), due to the formation of a frictionally stabilized contact network. Investigating how the molecular weight of the suspending solvent affects the frictional particle-particle interactions, we report on experiments with suspensions of fumed silica particles in polyethylene glycol (PEG). Focusing on the monomer-to-oligomer limit, with n = 1 to 8 ethylene oxide repeat units, we find that increasing n enhances shear thickening under steady-state shear and even elicits rapidly propagating shear jamming fronts, as assessed by high-speed ultrasound imaging of impact experiments. We associate this behavior with a weakening of the solvation layers surrounding the particles as n is increased, which thereby facilitates the formation of frictional contacts. We argue that for n larger than the monomer-to-oligomer limit the trend reverses and frictional interactions are diminished, as observed in prior experiments. This reversal occurs because the polymeric solvent transitions from being enthalpically bound to entropically bound to the particle surfaces, which strengthens solvation layers.
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Affiliation(s)
- Mike van der Naald
- James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois, USA.
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9
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Hsu CP, Mandal J, Ramakrishna SN, Spencer ND, Isa L. Exploring the roles of roughness, friction and adhesion in discontinuous shear thickening by means of thermo-responsive particles. Nat Commun 2021; 12:1477. [PMID: 33674607 PMCID: PMC7935878 DOI: 10.1038/s41467-021-21580-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 01/24/2021] [Indexed: 01/31/2023] Open
Abstract
Dense suspensions of colloidal or granular particles can display pronounced non-Newtonian behaviour, such as discontinuous shear thickening and shear jamming. The essential contribution of particle surface roughness and adhesive forces confirms that stress-activated frictional contacts can play a key role in these phenomena. Here, by employing a system of microparticles coated by responsive polymers, we report experimental evidence that the relative contributions of friction, adhesion, and surface roughness can be tuned in situ as a function of temperature. Modifying temperature during shear therefore allows contact conditions to be regulated, and discontinuous shear thickening to be switched on and off on demand. The macroscopic rheological response follows the dictates of independent single-particle characterization of adhesive and tribological properties, obtained by colloidal-probe atomic force microscopy. Our findings identify additional routes for the design of smart non-Newtonian fluids and open a way to more directly connect experiments to computational models of sheared suspensions.
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Affiliation(s)
- Chiao-Peng Hsu
- Laboratory for Soft Materials and Interfaces, Department of Materials, ETH Zurich, Zurich, Switzerland
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Zurich, Switzerland
| | - Joydeb Mandal
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Zurich, Switzerland
| | | | - Nicholas D Spencer
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Zurich, Switzerland
| | - Lucio Isa
- Laboratory for Soft Materials and Interfaces, Department of Materials, ETH Zurich, Zurich, Switzerland.
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10
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Singh A, Ness C, Seto R, de Pablo JJ, Jaeger HM. Shear Thickening and Jamming of Dense Suspensions: The "Roll" of Friction. PHYSICAL REVIEW LETTERS 2020; 124:248005. [PMID: 32639825 DOI: 10.1103/physrevlett.124.248005] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 05/20/2020] [Indexed: 06/11/2023]
Abstract
Particle-based simulations of discontinuous shear thickening (DST) and shear jamming (SJ) suspensions are used to study the role of stress-activated constraints, with an emphasis on resistance to gearlike rolling. Rolling friction decreases the volume fraction required for DST and SJ, in quantitative agreement with real-life suspensions with adhesive surface chemistries and "rough" particle shapes. It sets a distinct structure of the frictional force network compared to only sliding friction, and from a dynamical perspective leads to an increase in the velocity correlation length, in part responsible for the increased viscosity. The physics of rolling friction is thus a key element in achieving a comprehensive understanding of strongly shear-thickening materials.
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Affiliation(s)
- Abhinendra Singh
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- James Franck Institute, University of Chicago, Chicago, Illinois 60637, USA
| | - Christopher Ness
- School of Engineering, University of Edinburgh, Edinburgh EH9 3FG, United Kingdom
| | - Ryohei Seto
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325000, China
| | - Juan J de Pablo
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Heinrich M Jaeger
- James Franck Institute, University of Chicago, Chicago, Illinois 60637, USA
- Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
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11
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Guy BM, Ness C, Hermes M, Sawiak LJ, Sun J, Poon WCK. Testing the Wyart-Cates model for non-Brownian shear thickening using bidisperse suspensions. SOFT MATTER 2020; 16:229-237. [PMID: 31777908 DOI: 10.1039/c9sm00041k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
There is a growing consensus that shear thickening of concentrated dispersions is driven by the formation of stress-induced frictional contacts. The Wyart-Cates (WC) model of this phenomenon, in which the microphysics of the contacts enters solely via the fraction f of contacts that are frictional, can successfully fit flow curves for suspensions of weakly polydisperse spheres. However, its validity for "real-life", polydisperse suspensions has yet to be seriously tested. By performing systematic simulations on bidisperse mixtures of spheres, we show that the WC model applies only in the monodisperse limit and fails when substantial bidispersity is introduced. We trace the failure of the model to its inability to distinguish large-large, large-small and small-small frictional contacts. By fitting our data using a polydisperse analogue of f that depends separately on the fraction of each of these contact types, we show that the WC picture of shear thickening is incomplete. Systematic experiments on model shear-thickening suspensions corroborate our findings, but highlight important challenges in rigorously testing the WC model with real systems. Our results prompt new questions about the microphysics of thickening for both monodisperse and polydisperse systems.
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Affiliation(s)
- Ben M Guy
- School of Physics and Astronomy, University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.
| | - Christopher Ness
- School of Engineering, University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3JL, UK. and Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, UK
| | - Michiel Hermes
- School of Physics and Astronomy, University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK. and Soft Condensed Matter, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - Laura J Sawiak
- School of Physics and Astronomy, University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.
| | - Jin Sun
- School of Engineering, University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3JL, UK.
| | - Wilson C K Poon
- School of Physics and Astronomy, University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.
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