Séminaire Matière Molle : Nicolas Waisbord (Géosciences Rennes)

Séminaire Matière Molle par Nicolas Waisbord (Géosciences Rennes) : Complex and biological fluids flows in microfluidics model porous media: transport and critical phenomena.

Nicolas Waisbord, le 29 novembre 2019

Complex and biological fluids flows in microfluidics model porous media: transport and critical phenomena

Porous media flow studies often rely on the measurement of few quantities (flow rate, pressure drop or time series of a dispersed concentration pulse) integrated over opaque samples, and parametric modelling of the flow inside. The complexity of the geometry and the flow often introduces too many parameters to adjust. Because of their transparency, 2D microfluidic chips allow to investigate in situ the flow of Non-newtonian and active suspensions in porous geometry, to unveil the fine, multiscale (from the pore to the sample) physics at play. The first part of the talk will focus on Non-Newtonian fluids, showing how: (i) fluidized yield stress fluid (mayonaise) percolates discreetly across a saturated sample (ii) disorder supresses chaos in viscoelastic (tomato juice) flows. In a second part, the subject of cell motility in porous media will be tackled with (i) the giant Taylor dispersion of cells in a square lattice and (ii) the diodic transport of directed bacteria in porous media. These simple two dimensional microfluidics systems are enough to unveil novel physical phenomena; they also reveal their own limitations. In particular, the expected impact of the third dimension of natural systems will be debated at the end of the talk, as well as the innovative experimental solutions considered in the collaboration between Geosciences and IPR to explore it.