As shown in the illustration, a crack in the new material (top) is repaired by reaction with carbon dioxide. Source: MIT News/courtesy of the researchersMIT chemical engineers have designed a polymer material that can grow, strengthen and even repair itself, just by reacting with carbon dioxide from the air. The material continuously converts CO2 into a self-reinforcing carbon-based material, which could one day be used for construction, repair or protective coatings.

It could, for example, be made into panels of a lightweight matrix that could be shipped to a construction site. There, exposure to air and sunlight would cause the panels to harden and solidify – saving on both energy and the cost of transportation.

The synthetic, gel-like substance performs a chemical process similar to the way plants incorporate carbon dioxide into their growing tissues. In their proof-of-concept experiments, the MIT team made use of chloroplasts, the light-harnessing components within plant cells, obtained from spinach leaves. In their ongoing and future work, the researchers intend to replace the chloroplasts with non-biological catalysts.

The material is not yet strong enough to be used as a building material, but the researchers believe that commercial applications such as self-healing coatings and crack filling are realizable in the near term. Such materials would be self-repairing upon exposure to sunlight or some types of indoor lighting: If the surface gets scratched or cracked, the affected area would grow to fill in the gaps and repair the damage.

Previous efforts at developing self-healing materials that mimic the ability of biological organisms have required an active outside input to function – heating, ultraviolet light, mechanical stress, chemical treatment. The new material, which incorporates mass from the ubiquitous carbon in the atmosphere, needs nothing to activate the process apart from ambient light.

"Materials science has never produced anything like this," said Michael Strano, an MIT chemical engineering professor and one of the researchers involved in the study. “These materials mimic some aspects of something living, even though it's not reproducing."

The U.S. Department of Energy is sponsoring a new program directed by Strano to further develop the material, which opens a wide array of follow-up research.

Strano added that the work shows that carbon dioxide can be seen as an opportunity, and not merely an environmental cost.

“There's carbon everywhere,” he said. “We build the world with carbon. Humans are made of carbon. 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."

The research was published Oct. 9, 2018, in the journal Advanced Materials.