Magnetic Resonance Investigation of Pattern Formation in the Belousov-Zhabotinsky Reaction Dispersed in an AOT Water-in-Oil Microemulsion.

The proposed project is an experimental investigation of pattern formation in the Belousov-Zhabotinsky (BZ) reaction, dispersed in an AOT microemulsion medium: the BZ-AOT system. In the BZ reaction chemical waves and patterns are produced by coupling autocatalysis, a process whereby the rate of formation of key products accelerates, and diffusion, the process by which molecules move within a fluid. In a microemulsion medium the reactants of the BZ reaction predominantly reside within nanometre-sized water droplets, which are surrounded by surfactant (AOT) molecules, and are suspended in oil. The types of patterns produced can be tuned by controlling the concentration and size of water droplets within the oil. Amongst the rich variety of patterns exhibited, some previously unknown in other chemical systems, Turing structures are observed. This important type of pattern, where stationary waves are produced, has been proposed by Alan Turing in 1952 as the mechanism underpinning biological morphogenesis, the process by which organisms development form and structure. Other important patterns include dashed and segmented spiral waves, which mimic important biological patterns and have not been observed in other chemical systems. This project will use Magnetic Resonance Imaging (MRI) in this system, for the first time, to visualise patterns. This technique is based on Nuclear Magnetic Resonance (NMR), is non-invasive and can provide a wealth of chemical and physical information. The NMR signal is produced, by deflecting spinning nuclei (ie 1H) from their equilibrium positions, using radiofrequency pulses. Images are produce through application of magnetic field gradients, which can spatially locate nuclei by their spinning frequency, which is dependent on position. Image contrast is produced by differences in the density of nuclei or their relaxation time. It is the differences in relaxation time of the water molecules that will be exploited in imaging patterns in the BZ-AOT system.By using MRI, 3-dimensional (3D) patterns will be observed in the BZ-AOT system for the first time. Of significant importance, there is the opportunity to observe the first experimental example of 3D Turing patterns in a chemical system. MRI will also be used to probe the structure and dynamics of the microemulsion medium and better understand how it influences pattern formation and development. The diversity and complexity of patterns formed in this system is linked to differences in the diffusion co-efficients of key molecules in the BZ reaction. These will be measured using MRI experiments and relationships between pattern selection and development will be tested. Motivation for studying pattern formation in this system comes not only from the ability to better understand pattern formation in chemical systems, but also in its application to unravelling mechanisms underpinning biological wave and pattern formation.