Two-dimensional pattern formation in reaction-diffusion systems. Influence of the geometry

We present experimental results of the rich variety of two-dimensional precipitation patterns that are formed in a gel when varying some geometrical parameters. Because the patterns arise from a reaction-diffusion process of the typeA+B→C and the reagents as well as the gel are maintained always the same, the various shapes of the precipitate depend mainly on how the diffusion fronts carrying A and B meet each other. While Liesegang ring formation is predominant when the gel is inoculated with one of the reagents new possibilities appear when in an electrolyte-free agarose gel the diffusion fronts are forced to meet in different situations, because of the initial geometry of the reactants.