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These DARPA-funded bricks can self-repair—and replicate

While not as strong as concrete, the bricks could reduce the CO2 footprint of a building, self-heal, and even reproduce.

These DARPA-funded bricks can self-repair—and replicate
[Photo: University of Colorado Boulder College of Engineering and Applied Science]

Concrete may be one of mankind’s worst inventions. While it’s helped us build tall, sturdy buildings, it is causing more damage to our planet than any other material on Earth, largely due to its water use and the carbon footprint of its production. Specifically, grinding stone into clinker, the lumpy gray stuff you see in concrete, accounts for 50% of concrete’s carbon impact. There must be a better way.

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Researchers at the University of Colorado, operating under a grant from the Defense Advanced Research Projects Agency (DARPA), have demonstrated a new methodology to grow bricks out of bacteria and sand, in a new paper published in Matter. The technique uses cyanobacteria—or what you might know as green-glowing, carbon-sequestering algae—in a process that doesn’t sound all that different from mixing a yeast starter with flour to make bread. Though in this case, there’s no baking required.

[Photo: University of Colorado Boulder College of Engineering and Applied Science]

Scientists created a mix of sand and hydrogel (which is basically a special, goopy plastic that’s 90% water). Then they added the bacteria Synechococcus sp. PCC 7002, which is a particularly fast-growing, well-researched strain of cyanobacteria. Over the course of 24 hours, the bacteria produced rigid calcium (biology’s original hard stuff found in bones and shells), which bound the gel into a solid material.

The researchers say all of this can be done in a scaffold the size of a shoe box to produce a self-curing brick.

These “living brick materials” (LBMs) don’t have the strength of concrete, and they aren’t really designed to outright replace the material in the near future. “LBMs are not intended to broadly replace cementitious materials, but instead represent a new class of materials in which structural function is complemented by biological functionalities,” the paper explains.

[Photo: University of Colorado Boulder College of Engineering and Applied Science]

Instead, the bricks could be used in facades, or wherever you might use a standard brick. (Incidentally, the bacteria is bright green, but the bricks solidify to beige.) And what they lack in load-bearing qualities, they gain in flexibility. These bricks can stay alive over time, and under the right temperature and humidity, can even be spurred to repair their own cracks. And much like that aforementioned yeast starter, they can be reproduced easily in the field. Researchers have demonstrated that the material from one brick could be used to make multiple new bricks, meaning that you could create exponentially more bacterial building materials out of a single starter brick.

While the technology is still years away from application, it’s easy to imagine how these living bricks could help erect quick structures with limited access to supplies in remote locations, like deserts. They could also ensure you never have to tuckpoint your garage again.

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About the author

Mark Wilson is a senior writer at Fast Company who has written about design, technology, and culture for almost 15 years. His work has appeared at Gizmodo, Kotaku, PopMech, PopSci, Esquire, American Photo and Lucky Peach

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