Self-Healing Polymer Grows, Strengthens and Fixes Itself
Matthew Greenwood posted on October 22, 2018 |
Material reacts with carbon dioxide from the air to repair itself and get stronger.
Imagine a building material that, instead of cracking and weakening over time, actually gets stronger. That’s what a team of MIT chemical engineers may have just created

The polymer, which continuously converts carbon dioxide from the surrounding air into a carbon-based material that reinforces itself, could one day be used as construction or repair material, or as a protective coating. 

The material is a synthetic gel that absorbs carbon from the air in a process that is similar to the way in which plants absorb carbon dioxide to grow their tissues. It is made with aminopropyl methacrylamide and glucose, a glucose oxidase enzyme and chloroplasts—the light-capturing components inside plant cells (in this case from spinach leaves). 

The chloroplasts catalyze the reaction of carbon dioxide to glucose—but there’s a catch. Isolated chloroplasts are very unstable and stop functioning mere hours after being removed from the plant. However, Michael Strano, a professor of chemical engineering at MIT, and his colleagues have demonstrated methods to significantly increase the lifespan of chloroplasts, according to a paper published in Advanced Materials. The researchers’ long-term goal is to replace the chloroplasts with non-biological catalysts to improve their longevity. 

The material becomes stronger as it incorporates carbon. And while it isn’t strong enough yet to be used as a building material, it might be used to fill cracks or coat other materials in the near future. Additional advances in materials science are needed before construction materials could be created. The scientists are now focusing on optimizing the material’s self-healing properties. 

“This is a completely new concept in materials science,” said Strano. “What we call carbon-fixing materials don’t exist yet today” outside of the biological world, he notes. These materials can transform carbon dioxide into a solid, stable form—using only the power of sunlight, just as plants do. 

There has been a widespread effort to develop self-healing materials inspired by biological regeneration—but these have all needed an active outside trigger such as heat, UV light, physical stress or exposure to chemicals to activate them. The MIT team’s polymer, however, would only need ambient light and carbon particles already present in the air. 

An additional benefit of the polymer is that it would be removing a greenhouse gas from the air while repairing itself. “Our work shows that carbon dioxide need not be purely a burden and a cost,” Strano said. “Making a material that can access the abundant carbon all around us is a significant opportunity for materials science. In this way, our work is about making materials that are not just carbon neutral, but carbon negative.” 

Self-repairing materials could revolutionize industries from construction to apparel to medical research—and engineers like Strano and his team will continue to look to the natural world to create them. 

Read more about bio-inspired materials at The Significance of Completely Biodegradable 3D-Printed Plastic.

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