Séminaire Matière Molle : Olivia du Roure

Séminaire Matière Molle par Olivia du Roure (PMMH, ESPCI) le 17 mai 2019 à 11h (salle 120E)

Different morphologies of Individual, Brownian and Flexible fibers in microfluidic flows

Summary : The dynamics of an individual flexible objects in viscous flows is key to deciphering the rheological behavior of many complex fluids and soft materials. It also underlies a wealth of biophysical processes from flagellar propulsion to intracellular streaming. It results from the interaction between the object and the flow and depends on the properties of the object - flexibility, aspect ratio and dimensions - and the flow geometry and magnitude. This interaction is governed by the elasto-viscous number that compares elastic and viscous forces. In this seminar, I will focus more on the transport dynamics of actin filament, used here as a model of fluctuating flexible filament, in shear and pure straining flows. In  shear flow, the filament presents different morphologies depending on the elasto-viscous number. We recently described the complete phase diagram and the transition between the different modes of deformation. In pure straining flow, we observed a shape transition from a straight filament to a 3D helices. By comparing our experiments to two sets of very different simulations, we have shown that this transition is generic in the sense that neither fluctuations nor holding one  end is required. Finally this transition can be explained by linear stability analysis.