ERA

In order to contribute to the improvement of subsoil exploitation techniques for energy purposes, we make microsystems to study the fracture properties of natural and artificial clays, at various space and time scales, under various clay concentrations. The technology we propose allows to incorporate small inclusions, control the wetting properties of the materials at work, vary the formulation, etc.... We are interested primarily in the yield stress, strain localization and crack propagation. We make use of the advantages of microfluidic systems coupled to conventional and confocal optical microscopy to obtain a full dynamical image of the process. Strain fields are estimated by using either tracers in digital image correlation, or the clay birefringence. Experimental results are analyzed within a recently developped statistical framework, which successfully describes the complex rheology of soft glassy materials. This predictive framework, able to establish a link between local rearrangements and macroscopic mechanical response, will be extended in order to describe crack propagation. Using microfluidics for characterizing the response of models of subsoil materials to fracturation is an entirely novel approach, that may provide, in the field, information as relevant as micromodels for the oil industry. Moreover, the technology may easily be adapted for scanning rapidly the properties of many materials produced in several industrial contexts.