Use of advanced microscopy and microfluidics to study liquid process transformations in wormlike micellar systems

During the last decades, solutions of wormlike micelles have been successfully used in a number of diverse applications, for instance as proppants in oil industry, drag-reduction agents, heat-transfer fluids, and carrier in drug-delivery systems. One of the most extensive use of wormlike micelles is as additives in a wide variety of consumer goods, including hard-surface cleaners, dish-wash and laundry-detergents, body-soaps and shampoos. In fact, thanks to their reological properties, they act as thickener in such products, thereby ensuring the possibility to properly tune the viscoelastic behaviour of the final formulation. This is a particularly critical aspect for home-care and personal-care products, as high viscosity is desired to increase their stability, and to suspend particles, colorants and perfumes in the solution; on the other hand, elastic properties are required to ensure a proper dosage of the product, which otherwise couldn't flow through the pump of a dispenser, or would form filaments after being squeezed out of a bottle; finally, viscoelastic products appear more appealing to consumers. The widespread utilization of wormlike micelles is at the base of an huge industrial interest in understanding the flow-behaviour of these solutions. In fact, a constitutive model which describes these systems would allow a predictive analysis and modelling of the operation-units involved in manufacturing processes, such as pipes, tanks and static mixers, pumps and injector-nozzles, giving the possibility to predict industrially-relevant quantities, such as blending and pressure-drop. On the other hand, wormlike micellar systems generated a considerable interest in the basic research world, thanks to their rheological and flow-properties, characterized by the occurrence of several flow-instabilities, some of which haven't been observed in other complex fluids, and which look ubiquitous in such systems. In fact, due to the effect of the flow-deformation on the microstructure of the solution, wormlike micelles ...