Probing multi-scale dynamics of complex fluids and biological systems with differential dynamic microscopy

Imaging is, in its many forms, a cornerstone of modern science. From astronomy to cell biology, from medicine to material science, obtaining space-resolved maps - images - of the system under study is considered a key step in the process of "understanding" it. Nevertheless, and despite the common belief that "a picture is worth a thousand words", releasing the full informative potential of an image or an image sequence can be a challenging task, especially when the objects of interest are small, or the system is crowded, or the environment is complex, or the detection chain is noisy, or all these factors come into play together. In this seminar, I will introduce the basics of differential dynamic microscopy - an image analysis technique based on the study of time correlations in the spatial Fourier domain. DDM enables the extraction of statistically robust dynamic information from a sequence of images, even in conditions where a direct-space approach, based for example on image segmentation or particle tracking, would be difficult or impossible. I will discuss the potential and limitations of the method, presenting selected applications across a broad spectrum of physical and bio-soft matter systems. These include thermal fluctuations in complex fluids, collective cell migration, aging dynamics in amorphous solids, and flow patterns in biological fluids.