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The study of relaxation process and dynamic heterogeneities is crucial to rationalize the behaviour of many complex fluids, in which primary particles move in a crowded environment, including glasses, foams and gels as well as biological materials, such as cell tissues and micro-swimmers. However, the experimental characterization of these features is still complicated and handled by few specialized groups, as it requires resolving the dynamics in space and time and estimating deviations from the average behaviour.
Since soft glassy materials are widespread in industry and biology, an easy way to characterize the relaxation process and the emergence of dynamic heterogeneities is highly desirable. In this talk, I describe Differential Variance Analysis (DVA), a novel method that exactly does that, since it can be directly applied to digital videos of a sample, without tracking the single particle positions. Drawing on video microscopy of colloidal suspensions, I illustrate the strategy of this method, which starts by subtracting images at different lag-times and leads to quantify and directly visualize the structural relaxation process and the emergence of dynamic heterogeneities[1].
[1] R. Pastore, G. Pesce and M. Caggioni, Sci. Rep. 7, 43496 (2017)
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