Gel strip reactor

Figure A3.14.12. The first experimental observation of a Turing pattern in a gel strip reactor. Solutions containing separate components of the CIMA/CDIMA reaction are flowed along each edge of the strip and a spatial pattern along the horizontal axis develops for a range of experimental conditions. (Reprinted with pennission from [38], The American Physical Society.)...

Fig. 12.2 Continuously fed unstirred reactor (CFUR). Sketch of (a) gel strip reactor and (b) disk reactor. The grey rectangle represents the gel and its support. Patterns are viewed from the top...

Fig. 8. The Gel Strip Reactor and the first Turing pattern in the CIMA reaction, (a) Sketch of the reactor. Reagents well mixed in reservoirs A and B diffuse into the gel from the longest edges (b) Contrast enhanced picture of the pattern Several rows of clear spots. Dark regions correspond to reduced state colored dark blue. Clear regions correspond to oxidized state (c) Enlarged picture of the region of patterns. Scale is in mm. Experimental conditions temperature 7°C boundary feed concentrations [NaC102] = 2.6 x 10 M, [KI] = 3 x 10 M, [NaOH] = 3 X 10 M, [Na2S04] = 3 x IQ- M, [CH2(COOH)2] = 9 x 10" M, [H2SO4] = 10" M.

In the first set of experiments, we used a gel strip reactor , a geometry shown to be convenient as mentioned above. The core of our reactor is a thin strip of polyacrylamide gel 20 mm long, 1 mm thick, 3 mm wide (Figure 8a). The gel strip is squeezed between a white bottom plate and a Plexiglas cover... 

Fig. 11. Perspective view of a 3-D Tliring pattern in a gel strip reactor 3 mm thick. Partial view. The edges of the gel strip are underlined.

We have seen in Section 2.3 that to recover the uniformity of the control parameters in the plane of observation, one can resort to the disc reactor as initially proposed by the group in Austin [50,51]. A schematic representation of the disc reactor is given in Figure 12a. The piece of gel is now a flat disc fed by the two circular faces. Observations are made perpendicularly to the feed surfaces. The rows of patterns in the gel strip reactor correspond to planes filled with patterns in the disc reactor. As mentioned in Section 2.3, the pattern is still localized and tridimensional. 

Fig. 16, Travelling wave pattern. Strip reactor made of agarose gel (2% dry material) loaded with Thiodfene (6 g/liter of gel)[65]. All feed concentrations are as in Figure 15. The whole wave pattern moves from left to right at constant speed parallel to the feed surfaces. The bar inside the picture represents 1 mm.

A similar theoretical analysis can be reproduced for higher dimensional systems [48]. In a prospective paper [63], in collaboration with Pearson and Russo, we have reported preliminary results of a study of two-dimensional reaction-diffusion systems that model sustained front patterns observed in gel reactors. The linear [34, 35] and annular [21, 22, 38] gel reactors are strips of gel that are fed from the lateral boundaries. These reactors have a natural tendency to produce narrow front (linear or circular) structures away from the boundaries [39]. Stationary single-front and multi-front patterns have been observed experimentally [34-38]. According to the Hopf bifurcation mechanism reported in section 5, these front patterns are expected to destabilize into periodically oscillating structures. Since the Hopf mode is likely to be condensed in the active region at the front zones, the reaction-diffusion sys-... 

Those increasingly complex dynamics are thus very likely to be observed in the active region of the open gel reactors which is confined to the front, e.g. in a narrow linear (linear gel reactors) or circular (annular gel reactors) strip. The understanding of these dynamics provides a very exciting theoretical and... 

---