|Probing shear-induced rearrangements in Fourier space. II. Differential dynamic microscopy |
Ref HAL: hal-01982835_v1
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We discuss in two companion papers how Fourier-space measurements may be coupled to rheologicaltests in order to elucidate the relationship between mechanical properties and microscopic dynamics insoft matter. In this second companion paper, we focus on Differential Dynamic Microscopy (DDM)under shear. We highlight the analogies and the differences with dynamic light scattering coupled torheology, providing a theoretical approach and practical guidelines to separate the contributions toDDM arising from the affine and the non-affine part of the microscopic displacement field. We showthat in DDM under shear the coherence of the illuminating source plays a key role, determining theeffective sample thickness that is probed. Our theoretical analysis is validated by experiments on 2Dsamples and 3D gels.