MechE Colloquium: Pattern growth in flow-structured complex fluids

Abstract: Why is there so much structure, order and texture to life and nature, rather than a featureless expanse? From microscopic snowflakes to coral reefs and large-scale river networks, pattern formation leads to systems of extraordinary intricacy and beauty. Understanding how a system spontaneously selects its overall structure remains an ongoing scientific challenge. In this talk, we will discuss two examples of how flows, which push a material out of equilibrium and might be expected to destabilize textures, can instead structure complex fluids. We report the surprising emergence of chiral domains in a flowing nematic liquid crystal despite the achiral nature of the material. The chirality results from a periodic double-twist deformation of the liquid crystal and leads to striking stripe patterns vertical to the flow direction. In a second example, we show how shear-induced force chains in dense suspensions, induced by injection of pressurized air, lead to the growth of fractures and a subsequent relaxation of the suspension.

Biography: Irmgard Bischofberger is an experimentalist working in the fields of fluid dynamics and soft condensed matter. She obtained her Ph.D. degree in Physics from the University of Fribourg and has been a postdoctoral fellow in the Physics Department at the University of Chicago. She is currently an associate professor in the Department of Mechanical Engineering at MIT. Her research interests include the spontaneous pattern formation from fluid instabilities and drying processes and non-equilibrium phenomena in soft gels. Irmgard is passionate about communicating science to a diverse audience and has a longstanding ‘Science and Arts’ collaboration with artists and musicians.