Turing patterns in a simple gel reactor

Abstract

We introduce a very simple open two-dimensional gel reactor for studying chemical patterns that arise in reaction-diffusion systems. The reactor consists of a thin disk-shaped layer of polyvinyl alcohol gel with one face in direct contact with a well-stirred flow reactor containing reactants of the chlorite-iodide-malonic acid system; the other face of the gel is in contact with a piece of transparent plexiglass. We have used this reactor to study the transition from a uniform state to a hexagonal pattern; for other concentrations, striped patterns were observed. The wavelength of these structures is greater than the thickness of the gel layer, which indicates that the patterns are two-dimensional (a single layer). This reactor provides a promising new tool for studying chemical patterns since the diffusion time of reactants into and out of the gel can be made small compared to the total residence time in the stirred flow reactor. This feature facilitates the comparison between theory and experiment since the chemical concentrations leading to pattern formation are close to those in the stirred flow reactor and hence can be directly measured.

Linear Stability of Fractional Reaction - Diffusion Systems

“…Another interesting example is a gel medium. There separate experiments revealed instability ( in particular Turing patterns ) [21] and sub-diffusion [3]. Thus one can expect observations of Turing instability in sub-diffusive gel solvents.…”

Information-processing capabilities of chemical reaction-diffusion systems. 1. Belousov-Zhabotinsky media in hydrogel matrices and on solid supports

“…This value corresponds to the estimate of the timescale for diusion into and out of the gel. 9 The investigations performed have shown that the quality of images appearing in the media functioning in the gel matrix is signi®cantly better than in the case of the same reaction proceeding in the liquid phase. The gel matrix proved suitable for long-term repeated use after being washed with water.…”

Introduction to Nonequilibrium Phenomena

“…For example, employing the values of D u % 10 À9 (Reproduced from Ghiradella [1974] with permission). m 2 /s and q c % 10 4 m À1 to a gel reactor (Vigil et al, 1992), we estimated the diffusion constant as D u % 10 À15 m 2 /s for q c % 10 7 m À1 assuming the same reaction rate. Thus, the diffusion coefficient required for creating the color-producing pattern is estimated to be seven orders of magnitude smaller than that in water.…”