Control of chemo-hydrodynamic pattern formation by external localized cooling

Chemo-hydrodynamic patterns can form in a chemical two-layer system in a Hele-Shaw cell when each fluid contains separately a reactant of an exothermic neutralization reaction. When one reactant diffuses through the interface, the coupling between the chemical reaction and buoyancy-driven flows gives rise to complex spatio-temporal fingering near the interface. We show both experimentally and theoretically that such chemistry-driven fingering and its characteristics can be precisely controlled by external cooling applied locally along the sidewalls of the reactor. This control process gives a bright example of cooperative phenomena between chemistry and hydrodynamics and offers promising technological applications.