RUI: Pattern Formation in Reaction-Advection-Diffusion Systems with Lagrangian Chaos

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This individual investigator award funds experiments that will study the effects of fluid mixing on pattern formation in interacting fluid systems. The experiments will focus in particular on the role of Lagrangian chaos (chaotic mixing) on the pattern formation process. Two different fluid flows will be used: a blinking vortex flow, and an oscillating vortex chain in an annular configuration. Initially, the experiments will use the Belousov-Zhabotinsky reaction, an oscillatory chemical reaction, although studies will also be made with other interacting systems, such as liquid crystals or oil/wax systems undergoing phase transitions, and slime mold cultures. In addition to investigating the pattern formation process, the experiments will also test theoretical predictions about the effects of enhanced diffusive and superdiffusive transport on the propagation of reactive fronts. These experiments address an issue that is of great importance to a wide variety of systems (since flows are so common in reacting systems), and yet one that has received surprisingly little attention. In addition to helping to elucidate the pattern-formation processes, the results of the experiments will help in the future development of microfluidic devices in which chaos is the dominant mixing mechanism. The experiments will be performed with undergraduate students who will participate in all aspects of the research. These experiences form a valuable first step in the training of the next generation of scientists.There is a great deal of interest in the development of microfluidic devices - extremely small scale "factories" that process and produce chemical and biological agents in packages as small as an integrated circuit. This is just one example of a system in which fluid mixing plays a critical role in a reaction process. This NSF DMR award supports experiments that will study the interaction of fluid mixing and reaction in slow-moving, well-ordered flows (such as those in microfluidic devices). In particular, the experiments will explore the importance of chaotic mixing, which has been demonstrated to be the dominant mixing mechanisms for slow-moving and small-scale flows. The flows studied will be composed of vortices (whirlpools) that oscillate in a manner that results in chaotic mixing. Initially, the experiments will use chemical reactions, although studies will also be made with other interacting systems, such as liquid crystals, oil/wax systems and slime mold cultures. In addition to being relevant to the development of microfluidic devices, results from these studies may also help explain the behavior of plasmas in fusion reactors, the patterns that form during the fabrication of alloys from a melt, and the spreading of diseases during an epidemic. The experiments will be performed with undergraduate students who will participate in all aspects of the research. These experiences form a valuable first step in the training of the next generation of scientists.