Pattern selection by material aging: Modeling chemical gardens in two and three dimensions

What is it about?

The shapes of chemical gardens blur the line between inorganic chemistry and life. They encompass macroscopic structures such as hollow tubes formed by precipitation reactions. This paper presents the first model capable of simulating these shapes. The model is based on reaction-induced mechanical changes to the precipitate membranes that during aging decrease the material’s ability to elongate and stretch. It is formulated as a cellular automaton that applies two simple rules to a grid (similarly to the well-known “Game of Life” by John Conway). Each grid point is either occupied by one of the two reactant species or the solid product and membrane shapes expand under constant reactant injection.

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Photo by Pawel Czerwinski on Unsplash

Photo by Pawel Czerwinski on Unsplash

Why is it important?

Chemical gardens are a simple lab-bench model of hydrothermal vents that form huge precipitate structures on the ocean floor when hot mineral-rich water surges into the ocean. These precipitates and chemical gardens are subject to extremely steep concentration gradients that, together with spatial confinement to porous substructures, might have facilitated the emergence of life on our planet. Our work provides a macroscopic context for their description and also reveals a novel type of self-healing elasticity in which a material at the interface of two reactants can expand via micro-breaches and immediate product formation.

Perspectives