Marginal matters

Vitelli, Vincenzo; Hecke, Martin van

doi:10.1038/480325a

Cited by 12 publications

(7 citation statements)

References 9 publications

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“…This state is qualitatively different from DST in that it exhibits a yield stress, which we demonstrate explicitly by showing how it prevents weights from sinking in. Our findings suggest that DST does not correspond to a jammed but instead to a fragile state, which exhibits intermittent flow that can be thought of as a precursor to shear-jamming and exhibits behaviour of marginal material that is neither freely flowing nor fully jammed 20 .…”

mentioning

confidence: 74%

Direct observation of dynamic shear jamming in dense suspensions

Peters

Majumdar

Jaeger

2016

Nature

290

256

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Liquid-like at rest, dense suspensions of hard particles can undergo striking transformations in behaviour when agitated or sheared. These phenomena include solidification during rapid impact, as well as strong shear thickening characterized by discontinuous, orders-of-magnitude increases in suspension viscosity. Much of this highly non-Newtonian behaviour has recently been interpreted within the framework of a jamming transition. However, although jamming indeed induces solid-like rigidity, even a strongly shear-thickened state still flows and thus cannot be fully jammed. Furthermore, although suspensions are incompressible, the onset of rigidity in the standard jamming scenario requires an increase in particle density. Finally, whereas shear thickening occurs in the steady state, impact-induced solidification is transient. As a result, it has remained unclear how these dense suspension phenomena are related and how they are connected to jamming. Here we resolve this by systematically exploring both the steady-state and transient regimes with the same experimental system. We demonstrate that a fully jammed, solid-like state can be reached without compression and instead purely with shear, as recently proposed for dry granular systems. This state is created by transient shear-jamming fronts, which we track directly. We also show that shear stress, rather than shear rate, is the key control parameter. From these findings we map out a state diagram with particle density and shear stress as variables. We identify discontinuous shear thickening with a marginally jammed regime just below the onset of full, solid-like jamming. This state diagram provides a unifying framework, compatible with prior experimental and simulation results on dense suspensions, that connects steady-state and transient behaviour in terms of a dynamic shear-jamming process.

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mentioning

confidence: 74%

Direct observation of dynamic shear jamming in dense suspensions

Peters

Majumdar

Jaeger

2016

Nature

290

256

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“…Within this picture, we associate the transition at v p0 with the situation where the stress levels at the leading edge of the jamming front have reached σ 1 and are large enough for frictional interactions to occur. Thus, when v p < v p0 the suspension is in the lubrication regime, but when v p > v p0 it transitions into a fragile state with behaviour intermediate between solid and fluid 16 30 31 , as frictional contacts start percolating through the system to form a load-bearing network, eventually reaching a shear-jammed state as v p increases further. We point out that a non-zero shear modulus is not strictly necessary for the front to propagate (with k >0).…”

Section: Discussionmentioning

confidence: 99%

High-speed ultrasound imaging in dense suspensions reveals impact-activated solidification due to dynamic shear jamming

2016

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A remarkable property of dense suspensions is that they can transform from liquid-like at rest to solid-like under sudden impact. Previous work showed that this impact-induced solidification involves rapidly moving jamming fronts; however, details of this process have remained unresolved. Here we use high-speed ultrasound imaging to probe non-invasively how the interior of a dense suspension responds to impact. Measuring the speed of sound we demonstrate that the solidification proceeds without a detectable increase in packing fraction, and imaging the evolving flow field we find that the shear intensity is maximized right at the jamming front. Taken together, this provides direct experimental evidence for jamming by shear, rather than densification, as driving the transformation to solid-like behaviour. On the basis of these findings we propose a new model to explain the anisotropy in the propagation speed of the fronts and delineate the onset conditions for dynamic shear jamming in suspensions.

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“…A jammed system is said to be solid-like because, within the experimental time scale, it can resist applied stress by deforming elastically, as do coffee beans that become jammed in a chute, whereas an unjammed system will always flow. 14,15,17,20,22,23 In inert soft condensed matter, similar behavior is called kinetic arrest.…”

Section: Kinetic Arrestmentioning

confidence: 99%

“…22,23 If true, the jamming hypothesis would imply that specific events at the molecular scale necessarily modulate and respond to cooperative heterogeneities caused by jamming at a much larger scale of organization, but specific events at the molecular scale could never by themselves explain these cooperative large-scale events (Fig. 5).…”

Section: Bridging Biology and Physicsmentioning

confidence: 99%

Collective migration and cell jamming

et al. 2013

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Our traditional physical picture holds with the intuitive notion that each individual cell comprising the cellular collective senses signals or gradients and then mobilizes physical forces in response. Those forces, in turn, drive local cellular motions from which collective cellular migrations emerge. Although it does not account for spontaneous noisy fluctuations that can be quite large, the tacit assumption has been one of linear causality in which systematic local motions, on average, are the shadow of local forces, and these local forces are the shadow of the local signals. New lines of evidence now suggest a rather different physical picture in which dominant mechanical events may not be local, the cascade of mechanical causality may be not so linear, and, surprisingly, the fluctuations may not be noise as much as they are an essential feature of mechanism. Here we argue for a novel synthesis in which fluctuations and non-local cooperative events that typify the cellular collective might be illuminated by the unifying concept of cell jamming. Jamming has the potential to pull together diverse factors that are already known to contribute but previously had been considered for the most part as acting separately and independently. These include cellular crowding, intercellular force transmission, cadherin-dependent cell-cell adhesion, integrin-dependent cell-substrate adhesion, myosin-dependent motile force and contractility, actin-dependent deformability, proliferation, compression and stretch.

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Marginal matters

Cited by 12 publications

References 9 publications

Direct observation of dynamic shear jamming in dense suspensions

Direct observation of dynamic shear jamming in dense suspensions

High-speed ultrasound imaging in dense suspensions reveals impact-activated solidification due to dynamic shear jamming

Collective migration and cell jamming

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