Symmetry Breaking in Chemical Systems: Engineering Complexity Through Self-Organization and Marangoni Flows.

Area of Science:

• Physical Chemistry
• Chemical Physics
• Fluid Dynamics

Background:

• Reaction-diffusion systems exhibit complex spatio-temporal dynamics, forming patterns and waves.
• Fluid motion can disrupt self-organized concentration patterns in chemical and biological systems.

Purpose of the Study:

• To investigate the influence of Marangoni-driven flows on chemical wave dynamics.
• To understand how fluid motion around hydrophilic obstacles affects wave propagation in the modified Belousov-Zhabotinsky reaction.

Main Methods:

• Experimental observation of chemical waves in a thin fluid layer around hydrophilic obstacles.
• Comparison of wave patterns in covered (minimal evaporation) and uncovered (significant evaporation) setups.
• Numerical analysis to determine the dominant Marangoni forces (solutal vs. thermal).

Main Results:

• Circular waves initiated at obstacles propagated outwards.
• Covered setup: circular wavefronts maintained shape.
• Uncovered setup: Marangoni flows and gravity destabilized wavefronts, forming flower-like patterns.
• Pattern formation (petal number) correlated linearly with obstacle diameter above a minimum threshold.
• Solutal Marangoni forces were found to dominate thermal forces.

Conclusions:

• Marangoni-driven flows significantly alter chemical wave propagation, leading to pattern formation.
• The study demonstrates the ability to engineer specific wave patterns by controlling fluid dynamics.
• Findings are relevant for precise control of reaction dynamics in microfluidic devices.