Two new building materials that could defend cities against earthquakes and floods

Imagine if bridges were made with cement that could repair itself in an earthquake. And ships were coated in a protective shell that could patch itself if damaged by debris. We're closer than you think. Here are two kinds of self-healing materials that could revolutionize the way we build cities and vehicles.

Illustration by Sergey150770/Shutterstock

Self-healing material is any kind of substance that has the ability to repair itself. Often modeled on biological systems, they promise a future where our homes repaint themselves, and artificial limbs heal like real ones. Chemist Martin Hager and colleagues offer a good introduction to state-of-the-art materials that heal in a recent article, where they outline a few ways that materials heal themselves. Some polymers, for example, already have the ability to knit back together. This is called "intrinsic" healing." But most self-healing is caused by researchers adding to existing materials: They may put bacteria into concrete, for example, or sprinkle tiny capsules of a glue-like substance into sealants used on ships. That's "extrinsic" healing.

The gold ring, for scientists, is a material that heals by sensing that it's damaged. So far, we don't have very many of those. But we have plenty of materials that heal when exposed to water or heat.

Self-Healing Industrial Coatings

Autonomic Materials is a company that sells self-healing coatings for ships and large industrial equipment. Most of these machines are coated in polymers that protect against weathering which can lead to fatal malfunctions. This company offers a number of coatings that sense cracks and use tiny capsules filled with resins to fill the damaged areas with a new layer of the shell.

Self-Healing Concrete

Civil engineer Henk Jonkers mixes bacteria into concrete to create what he calls bio-concrete, a substance that fills in its own cracks and holes. What happens is that the bacteria grow into cracks as they form, releasing calcium carbonate, a substance similar to limestone. The result? As Jonkers shows us in this video, the cracks are filled in with what is essentially the waste material of these bacteria, who are engineered from extremophile bacteria that thrive in extremely dry conditions.

Additional reporting by Robert Gonzalez