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Self-healing bacteria bricks could help us build on the moon or Mars

This construction Franken-material's alive -- and it could be a more sustainable solution for building.

Scientists from the University of Colorado Boulder shaped their material made of sand, bacteria and gel into various shapes to show its versatility.

CU Boulder College of Engineering and Applied Science
This story is part of Welcome to Mars, our series exploring the red planet.

Future buildings may be teeming with bacteria, with scientists developing a hybrid construction material, made of microbes, that may be capable of repairing itself or even pulling carbon dioxide out of the air.

Wil Srubar, a professor at the University of Colorado Boulder, headed up an interdisciplinary team that used bacteria to create a durable "living" building material that would, among other tricks, be able to heal its own cracks. That would be an especially valuable asset in extreme conditions or military structures, the scientists say, as bricks made from the material could fix themselves after natural disasters or damage from enemy fire.

"We believe this material is particularly suitable in resource-scarce environments, such as deserts or the Arctic, even human settlements on other planets," Srubar, who founded a living-materials lab at the university that takes inspiration from nature, told me. "The sky is the limit, really, for creative applications of the technology."

Professor Wil Srubar and grad student Sarah Williams examine their Franken-material in the lab.

CU Boulder College of Engineering and Applied Science

The living building material arose from Srubar's interest in sustainable building. You can't buy these wonder bricks at your nearby Home Depot yet, but the researchers say they'd ultimately be cheaper to produce, and would remove carbon dioxide from the air rather than emit it.

"Living building materials could be used to improve the efficiency and sustainability of building material production and could allow materials to sense and interact with their environment," Chelsea Heveran, co-lead of a study on the research that came out last week in the journal Matter.

Living bricks could, for example, change color to indicate the presence of dangerous toxins, and potentially suck them up.

To make their bricks, the researchers blended bacteria into a "scaffold" made from gelatin and sand. Under the right light and other conditions, the microbes absorb carbon dioxide to help them grow and make calcium carbonate, the main ingredient in cement. The scientists can then mold this bacteria-scaffold mix into varying shapes. The team showed they could produce small cubes, bricks the size of shoeboxes and structures that look like fancy sandcastles.

"What is exciting is that while less than 1% of bacteria used in concrete self-sealing applications typically survive, we showed up to orders of magnitude higher survivability of bacteria in our material," Srubar said.

Approximately 9 to 14% of the bacterial colonies were still alive after 30 days and three different generations in brick form, according to the study. Chop one of the bricks in half, and each half is capable of growing into a new brick, it says.

The material is durable, too. The team discovered that under a variety of temperature and humidity conditions, it has about the same strength as mortar used by contractors today.

"You can step on it, and it won't break," Srubar said.

Microbes take shape in the mold.

CU Boulder College of Engineering and Applied Science

Self-healing materials have become attractive to science in a world increasingly conscious of e-waste.

Last year, scientists in Singapore developed a touch-sensitive, self-healing electronic skin that could be used to make for more realistic human interaction with machines like soft robots. The researchers showed that if the skin got cut or torn, it can stitch itself back together within days.

NASA is even looking into the possibility of self-healing spacesuits.

The work out of University of Colorado Boulder is supported by the Defense Advanced Research Projects Agency, or DARPA. Next up, Srubar says, is continuing to optimize the material's formula, and exploring other living organisms that could afford living bricks even more advantages.

"While we are at the beginning stages of this research," he said, "we expect the material will be available commercially within the next five to 10 years."