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Illuminating complex dynamics in soft matter with Laser Speckle Imaging

Joris Sprakel SprakelLab - Department of Physical Chemistry and Soft Matter, Wageningen University

In our team, we aim to establishing the simple rules that underlie molecular complexity in manmade and biological soft materials. To do so, in the past, we have worked extensively with a variety of conventional quantitative imaging methods. However, the inherent constraints of light penetration and photon localization, restricted these investigations to optically transparent materials. In the past years, our team has worked on exploring imaging in the limit of diffuse light scattering, to probe the internal thermal and mechanical motions of even the most opaque and absorptive materials. In this talk I will showcase how we have developed Laser Speckle Imaging, the imaging equivalent of Diffusing Wave Spectroscopy, developed originally as a qualitative tool for blood flow visualization in the medical world, into a highly resolved and sensitive technique for the quantitative mapping of dynamics in a wide variety of materials. I will discuss the principles behind the method and illustrates its versatility along a few examples, ranging from the visualization of drying and instabilities in paints, the microscopic mechanisms of repair in a self-healing polymer, to the identification of minute fracture precursors in the mechanical failure of a filled rubber.