Since the mid-1600s, chemists have been fascinated by the brightly colored, coral-like structures formed by mixing metallic salts in a small bottle.
Until now, researchers have been unable to model how these deceptively simple tubular structures—called chemical gardens—work and the patterns and rules that govern their formation.
In a paper published in Proceedings of the National Academy of SciencesFlorida State University researchers have outlined a model that explains how these structures grow upward, form different shapes and how they go from a flexible, self-healing that material into a more brittle one.
“In the context of the material, it’s very interesting,” said FSU Professor of Chemistry and Biochemistry Oliver Steinbock. “They don’t grow like crystals. A crystal has nice sharp corners and grows atom layer by atom layer. And if a hole happens in a chemical garden, it heals itself. These are the early steps in learning how to make materials that can regenerate and heal themselves.”
Usually, chemical gardens are formed when metal salt particles are placed in a silicate solution. The dissolved salt reacts with the solution to create a semipermeable membrane that protrudes upward from the solution, creating a biological-looking structure, similar to coral.
Scientists observed chemical gardens for the first time in 1646 and for many years were amazed by their fascinating formations. The chemistry is related to the formation of hydrothermal vents and the corrosion of steel surfaces where unmelted tubes form.
“People are realizing that these are extraordinary things,” Steinbock said. “They have a very long history in chemistry. It used to be more like a demonstration experiment, but in the last 10-20 years, scientists have become interested in them again.”
The inspiration for the mathematical model developed by Steinbock, along with postdoctoral researcher Bruno Batista and graduate student Amari Morris, came from experiments that continuously inject a salt solution into a more large amount of silicate solution between two horizontal plates. It shows different ways of growing and that the material starts out as elastic, but as it ages, the material becomes harder and more likely to break.
The confinement between the two layers allows the researchers to simulate a number of different shaped patterns, some of which seem to be flowers, hair, spirals and worms.
In their model, the researchers describe how these patterns emerged over the course of the chemical garden’s development. Salt solutions may differ in chemical composition, but their model explains the universality of the formation.
For example, patterns may consist of loose particles, folded membranes, or self-expanding filaments. The model also confirmed observations that fresh membranes expand in response to microbreaches, demonstrating the material’s self-healing capabilities.
“The good thing we got is that we got the essence of what it takes to describe the shape and growth of chemical gardens,” Batista said.
More information:
Batista, Bruno C. et al, Pattern selection through material aging: Modeling chemical gardens in two and three dimensions, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2305172120. doi.org/10.1073/pnas.2305172120
Provided by Florida State University
Citation: Planting seeds: Researchers study how to grow chemical gardens (2023, July 3) retrieved on 4 July 2023 from https://phys.org/news/2023-07-seeds- chemical-gardens.html
This document is subject to copyright. Except for any fair dealing for the purpose of private study or research, no part may be reproduced without written permission. Content is provided for informational purposes only.