Position echo experiment

Concentrated emulsions experience non-linear flow for small shear amplitudes. These non-linearities are two small to be detected through mechanical measurements. We present a new experiment that aims at detecting them. The key idea of the experiment consists in periodically shearing the system, and, thanks to diffusing wave spectroscopy, counting droplets that experience non-periodic motions. We show that the flow of these systems is extremely heterogeneous, and that deformation is concentrated in small fragile regions.