‘Living bricks’ that reproduce could cut construction’s carbon footprint (chemistry)


EXCERPTS: In a study that will appear Jan. 15 in the journal Matter, engineer Wil Srubar and his colleagues describe their strategy for using bacteria to develop building materials that live and multiply -- and might deliver a lower carbon footprint, to boot. "We already use biological materials in our buildings, like wood, but those materials are no longer alive" said Srubar [...] "We're asking: Why can't we keep them alive and have that biology do something beneficial, too?"

[...] the researchers say that their ability to keep their bacteria alive with a high success rate shows that living buildings might not be too far off in the future. Such structures could, one day, heal their own cracks, suck up dangerous toxins from the air or even glow on command. "The sky's the limit for our creativity," Srubar said.

[...] The technique capitalises on the process of biomineralisation, whereby living organisms produce minerals that can harden or stiffen tissue. The inspiration came in part from the limitations of self-healing concrete, itself a biomineralisation success story.

Here an inoculum of biomineralising bacteria is added to cement to heal cracks. However, the environment of cement is not conducive to biological growth. ‘We showed that you can obtain greater survivability of the bacteria if you rethink the environment that you put them in,’ explains Wil Srubar, part of the team at the Unviersity of Colorado, Boulder that came up with the bricks.

In this system bacteria are placed in an environment that is more conducive to growth and through the biomineralisation process they contribute to the structural formation of the material. According to Srubar, ‘the compressive strength and mechanical properties we achieved are on the order of a cementitious mortar, like what you would see between the bricks in your house’.

The other advantage to increased survivability is that the bricks can be exponentially manufactured. Just like cell division, a parent brick can be divided to produce two new bricks. Srubar and his team were able to repeat the process for three generations in a single week, obtaining eight bricks from the original parent. The process involves heating the divided bricks until they are a medium viscosity liquid–sand solution, adding new gel medium and simply allowing the bacteria to grow for roughly six hours. From here more sand is added and the cubes cooled and remolded to form new bricks.

The team’s challenge now is optimising the environment for the trade-off between the viability of the bacteria and structural capacity. [...] The team's cyanobacteria, for example, need humid conditions to survive -- something that's not possible in more arid regions of the world. So he and his team are working to engineer microbes that are more resistant to drying out so they remain alive and functional.

But the possibilities are big. Srubar imagines a future in which suppliers could mail out sacks filled with the desiccated ingredients for making living building materials. Just add water, and people on site could begin to grow and shape their own microbial homes. "Nature has figured out how to do a lot of things in a clever and efficient way," Srubar said. "We just need to pay more attention." (MORE - 1) ... (MORE - 2)

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