<i>Microfluidic flow-processing of soft matter systems</i>

Arguably one of the most striking properties of soft matter systems is the propensity to have a major response to minor perturbations. One of such perturbations is flow, which allows to induce phase changes and structural rearrangements. Here, two pseudo-quaternary systems containing sodium dodecyl sulfate (SDS) and medium to long chain alcohols as co-surfactants in a lamellar phase (Lα) are studied. The structural transformation from planar lamellar sheets to multilamellar vesicles (MLVs) is observed upon the application of shear stress to the solution. This transformation is characterised with nuclear magnetic resonance (NMR), rheology and small angle neutron scattering (SANS). Furthermore, the kinetics of the transformation is resolved with realtime measurements within a microfluidic device to obtain well-defined shear fields. Time-resolved kinetics are investigated by tracking the changes in birefringence pattern employing cross-polarised microscopy. The results point to MLV formation and indicate that it is a time-dependent and shearrate dependent process. The combination of microfluidics with high resolution spatio-temporal measurements allows characterisation of out-of-equilibrium transformations in complex surfactant mixtures.