Spontaneous brittle-to-ductile transition in aqueous foam

Arif, Shehla; Tsai, Jih-Chiang; Hilgenfeldt, Sascha

doi:10.1122/1.3687425

Cited by 20 publications

(38 citation statements)

References 42 publications

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“…Whereas rich physics has been revealed, these phenomena have yet to find implications in the broader technological context. Nevertheless, concentrated emulsions, bubble rafts, and colloids have long been used as models of crystals for studying grain boundaries, dislocations, plasticity, and other processes central to materials science and solid mechanics (11)(12)(13)(14)(15)(16). Such systems have not been applied to model the deformation modes of nanocrystals, however.…”

mentioning

confidence: 99%

Spatiotemporal periodicity of dislocation dynamics in a two-dimensional microfluidic crystal flowing in a tapered channel

Gai

Leong

Cai

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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When a many-body system is driven away from equilibrium, order can spontaneously emerge in places where disorder might be expected. Here we report an unexpected order in the flow of a concentrated emulsion in a tapered microfluidic channel. The velocity profiles of individual drops in the emulsion show periodic patterns in both space and time. Such periodic patterns appear surprising from both a fluid and a solid mechanics point of view. In particular, when the emulsion is considered as a soft crystal under extrusion, a disordered scenario might be expected based on the stochastic nature of dislocation dynamics in microscopic crystals. However, an orchestrated sequence of dislocation nucleation and migration is observed to give rise to a highly ordered deformation mode. This discovery suggests that nanocrystals can be made to deform more controllably than previously thought. It can also lead to novel flow control and mixing strategies in droplet microfluidics.many-body system | order | microfluidic crystal | dislocation dynamics | plasticity T he emergence of order and spontaneous self-organization have been of long-standing interest (1). They are key not only to the understanding of complex phenomena from chemical oscillators to swarming behavior in animals (2, 3), but also to novel engineering solutions if harnessed (4, 5). Two-phase flow in microfluidics offers a simple platform for the study of dissipative nonequilibrium systems, where hydrodynamic interactions have led to the emergence of collective dynamics and order (6-10). Most works thus far have focused on dilute emulsions or foams in simple channel geometries. Whereas rich physics has been revealed, these phenomena have yet to find implications in the broader technological context. Nevertheless, concentrated emulsions, bubble rafts, and colloids have long been used as models of crystals for studying grain boundaries, dislocations, plasticity, and other processes central to materials science and solid mechanics (11-16). Such systems have not been applied to model the deformation modes of nanocrystals, however. Recent work on crystal plasticity in microscopic samples found that in contrast to their macroscopic counterparts, both the external geometry and internal structure of the material determine material strength (17). Furthermore, the size and timing of dislocation-induced strain bursts are found to be intermittent, stochastic, and unpredictable (17-20). The stochastic nature of dislocation dynamics complicates the control of the shape of the materials during deformation, and renders their subsequent manipulation and manufacturing challenging (18). What is unknown, however, is whether plasticity remains stochastic as the sample shrinks to the nanoscale, and whether the dimensionality and loading conditions influence the stochasticity. Given the increasing importance of low-dimensional nanodevices in applications from optoelectronics to energy conversion, it is critical to understand how nanomaterials can be shaped, manipulated, and manufactured.In t...

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confidence: 99%

Spatiotemporal periodicity of dislocation dynamics in a two-dimensional microfluidic crystal flowing in a tapered channel

Gai

Leong

Cai

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…Much as in crystalline atomic solids, these mechanisms can be termed brittle and ductile: in the former case observed for large rates of applied pressure, very fast cleavages of the foam are sustained with very little deformation around the crack surface. These brittle cracks proceed by successive breakage of the thin films between foams in almost perfect sequence along the pressure gradient [7,8]. In the latter case, observed for smaller rates of applied pressure, a much slower air/foam interface propagation is observed [9], morphologically resembling a fingering instability in homogeneous fluid systems described by Saffman and Taylor [10] and studied extensively as an example of nonlinear instability and shape selection [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Cracks and fingers: Dynamics of ductile fracture in an aqueous foam

Stewart

Hilgenfeldt

2017

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…To measure such a minimal velocity, we have considered experiments where a spontaneous fragile-ductile transition occurs, as considered also in [15]; we then take the displacement of the crack tip between the two images in the fragile regime closest to the transition as an estimate of the minimal velocity of fragile propagation v min . There is a significant uncertainty in this measurement, since the displacement of the fragile crack tip is quantised by the number of broken films between two consecutive images, which is usually 3 or 4; hence, we ascribe a rela- tive uncertainty of 30% on v min .…”

Section: Minimal Velocity In the Fragile Regimementioning

confidence: 99%

“…Initially motivated by pattern formation [13,14], this configuration was shown by Hilgenfeldt and coworkers to be ideal to study the limit of stability of a flowing foam [1,15]. They showed that the injected air can propagate either in a ductile regime, pushing bubbles apart by plastic rearrangements without bursting; or in a fragile regime, breaking series of soap films to form narrow cracks, like fracture in brittle materials [16].…”

Section: Introductionmentioning

confidence: 99%

“…To study the opposite interfacial behaviour, we will show results with a surfactant mixture giving incompressible interfaces. Second, we will test the critical velocities proposed by Hilgenfeldt and colleagues [1,15], namely the maximal velocity of ductile fracture and the minimal velocity of brittle fracture. Third, we will describe branching effects in the regime of fragile fracture.…”

Section: Introductionmentioning

confidence: 99%

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Response of a two-dimensional liquid foam to air injection: Influence of surfactants, critical velocities and branched fracture

Salem

Cantat

Dollet

2013

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Experiments where air is injected into a foam confined in a Hele-Shaw cell are convenient to study the rheology of foams far from the quasistatic regime, and their limit of stability. At low overpressure, the injected air forms a ductile crack, whereas at high overpressure, it breaks the foam like a brittle material. We present new results in this configuration, complementary with previous studies. We show that air injection is slowed down for surfactants giving incompressible interfaces instead of mobile ones. The injection rate is quantitatively captured by a simple model balancing the air overpressure with known foam/wall friction laws for incompressible interfaces. We also revisit the critical velocity criteria for the injected air proposed by Arif et al. [1]. The upper bound of velocity in the ductile regime, based on the resistance of soap films against wall friction, is shown to hold much better for mobile than for incompressible interfaces. The propagation speed of shear waves is confirmed to be a good lower bound for the velocity in the brittle regime, provided the motion of all liquid within the foam is accounted for. Finally, a short description of branching in the fragile regime is given.

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Spontaneous brittle-to-ductile transition in aqueous foam

Cited by 20 publications

References 42 publications

Spatiotemporal periodicity of dislocation dynamics in a two-dimensional microfluidic crystal flowing in a tapered channel

Spatiotemporal periodicity of dislocation dynamics in a two-dimensional microfluidic crystal flowing in a tapered channel

Cracks and fingers: Dynamics of ductile fracture in an aqueous foam

Response of a two-dimensional liquid foam to air injection: Influence of surfactants, critical velocities and branched fracture

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