Dynamics of fronts in chemical and bacterial media:
If you’ve seen one front, you’ve seen them all
Self-propagating reaction fronts occur in many chemical and physical systems possessing two key ingredients: a reactive medium (for example a fuel-air mixture in the case of flames) and an autocatalyst that is a product of the reaction that also accelerates the reaction (for example thermal energy in the case of flames). Self-propagation occurs when the autocatalyst diffuses into the reactive medium, initiating reaction and creating more autocatalyst. This enables reaction-diffusion fronts to propagate at steady rates far from any initiation site. In addition to flames, propagating fronts have been observed in aqueous reactions, free-radical initiated polymerization processes and even propagating fronts of motile bacteria such as E. coli. This talk will focus on a comparison of the dynamics of these four different types of fronts including propagation rates, extinction conditions and instability mechanisms. Our research has shown that despite the disparate nature of the reactants and autocatalysts in these four systems, remarkably similar dynamical behavior is observed since the underlying driving mechanisms for propagation are similar. The key role of loss mechanisms (heat, chemical species or cell death) and differential diffusion of reactant and autocatalyst ("Lewis number") is demonstrated.