Direct evidence of plastic events and dynamic heterogeneities in soft-glasses

• Published in: Soft matter 2014-07, Vol.1 (26), p.4615-4624
• Main Authors: Benzi, R, Sbragaglia, M, Perlekar, P, Bernaschi, M, Succi, S, Toschi, F
• Format: Article
• Language: English
• Subjects: Correlation; Droplets; Dynamical systems; Dynamics; Heterogeneity; Segregations; Stresses; Yield stress
• ISSN: 1744-683X; 1744-6848
• DOI: 10.1039/c4sm00348a

By using fluid-kinetic simulations of confined and concentrated emulsion droplets, we investigate the nature of space non-homogeneity in soft-glassy dynamics and provide quantitative measurements of the statistical features of plastic events in the proximity of the yield-stress threshold. Above the yield stress, our results show the existence of a finite stress correlation scale, which can be mapped directly onto the cooperativity scale , recently introduced in the literature to capture non-local effects in the soft-glassy dynamics. In this regime, the emergence of a separate boundary (wall) rheology with higher fluidity than the bulk is highlighted in terms of near-wall spontaneous segregation of plastic events. Near the yield stress, where the cooperativity scale cannot be estimated with sufficient accuracy, the system shows a clear increase of the stress correlation scale, whereas plastic events exhibit intermittent clustering in time, with no preferential spatial location. A quantitative measurement of the space-time correlation associated with the motion of the interface of the droplets is key to spot the elastic rigidity of the system. By using fluid-kinetic simulations of confined and concentrated emulsion droplets, we investigate the nature of space non-homogeneity in soft-glassy dynamics and provide quantitative measurements of the statistical features of plastic events in the proximity of the yield-stress threshold.