Physical interactions in non-ideal fluids promote Turing patterns.

Area of Science:

• Chemical kinetics
• Pattern formation
• Theoretical chemistry

Background:

• Turing's mechanism explains natural periodic patterns via reaction-diffusion systems.
• Formation requires slow activator diffusion and nonlinear reactions, often from cooperativity.
• Experimental evidence for Turing patterns remains limited.

Purpose of the Study:

• To investigate the impact of direct physical interactions between chemical species on Turing pattern formation.
• To explore how these interactions modify the conditions for pattern emergence and characteristics.
• To bridge the gap between traditional Turing patterns and chemically active phase separation.

Main Methods:

• Theoretical modeling of reaction-diffusion systems incorporating direct intermolecular interactions.
• Analysis of how activator-inhibitor repulsion affects differential diffusivity and reaction nonlinearity.
• Examination of pattern formation under strong interaction conditions, including phase separation.

Main Results:

• Weak repulsion between activator and inhibitor substantially reduces required differential diffusivity and reaction nonlinearity.
• Strong interactions can lead to phase separation, but pattern length scales remain governed by reaction-diffusion dynamics.
• Direct interactions significantly alter Turing pattern characteristics, deviating from predictions based solely on reaction-diffusion.

Conclusions:

• Direct physical interactions are critical and must be included in models of realistic reaction-diffusion systems.
• The theory unifies Turing patterns with chemically active phase separation, broadening applicability.
• Even minor interactions have a substantial effect, necessitating their consideration for accurate pattern prediction.