A building’s skin and bones—literally? The coming world of engineered living materials

When lightning strikes, a tree can often repair the damage by generating another layer of bark to cover the gash. But if that same bolt from above lashes a wood-frame house instead, call the remodelers. Even though the house’s exterior walls are essentially made of trees, the material lost its adaptive quality when lumberjacks felled those mighty pines or oaks.

In the words of scientist Justin Gallivan of the U.S. Defense Advanced Research Projects Agency (DARPA), wood is “rendered inert” when a tree is chopped down. That neutralizes all the advantages of a living material. In their natural state, trees react and adapt to wounds and the weather. So do coral reefs—not to mention your own skin.

What if living materials, with those same self-healing properties, could be grown artificially to the size and strength required to construct a house? Or a skyscraper? Is that possible? That’s what DARPA wants to find out. The agency is soliciting research proposals aimed at the creation of what it calls “engineered living materials (ELM).”

elm_composite

DARPA envisions walls that fix themselves, non-fading surfaces, and driveways that absorb oil spills without a trace. (Source: DARPA)

“Imagine that instead of shipping finished materials, we can ship precursors and rapidly grow them on site using local resources,” Gallivan said to the press in August when announcing the ELM program. “And, since the materials will be alive, they will be able to respond to changes in their environment and heal themselves in response to damage.”

Today, a building’s envelope is often called its “skin,” while the steel frame of a building is known as its skeletal structure, or even its “bones.” In DARPA’s imagined future, these terms will cease to be merely rhetorical. And the sustainability benefits of bio-building might be substantial, when you consider the carbon emissions generated in the production of conventional materials such as concrete.

But DARPA didn’t pull this sci-fi-sounding concept out of thin air. Biochemists and engineers around the globe are already tinkering with limited forms of biomimetic (or life-imitating) materials, as you’ll see below. Gallivan’s vision of self-healing living walls is perhaps the logical extension of these various technologies, and the ELM program might prove the catalyst needed for skin-and-bone to replace brick-and-mortar.

Bacteria brickyard

One inspiration for the ELM program is a start-up that grows bricks in a lab. Yes, grows. The idea occurred to architect Ginger Dosier when she learned that coral polyps—tiny marine animals—create the hard, rocklike substance sandstone naturally. She co-founded the company, bioMASON, with her husband, Michael—like her, an architect and a self-taught scientist. (They have help from a staff of college-taught scientists.)

bio-bricks-image

The lab-grown bricks. (Source: bioMASON)

In their lab in North Carolina’s Research Triangle, the bioMASON team places sand into molds and injects it with trillions of microorganisms (Sporosarcina pasteurii, if you must know), which they feed water and a calcium solution. The bacteria bind with the grains of sand, generating a natural cement that becomes heavy and hardens. The bricks are ready in two to five days.

Compare that with the way traditional bricks are manufactured, by digging up clay (which could be better put to use in agricultural soil) and firing it in a kiln at 2,000 degrees for three to five days. This process uses up lots of fuel and releases carbon dioxide into the atmosphere—800 million tons of it per year, by some estimates. Keep in mind, brick is still the most common building material worldwide, with Asia alone making 1.2 trillion bricks a year.

According to Acorn Innovestments, which provided bioMASON with seed funds, third-party testing determined that the bio-bricks have a strength comparable to traditional masonry, though for now, the start-up is only selling the bricks for use in paving. The bioMASON lab can produce 1,500 bricks a week, and they’re moving next month to a larger facility that will enable them to make 5,000 bricks every two days.

But the Dosiers hope to truly make an impact by shipping the bacteria solution—just one hand-held vial can make 500 bricks—across the globe to builders who can mix it with local sand, whether from nearby deserts (looking at you, Los Angeles) or quarries.

Blood, corn, and bone

The Dosiers aren’t the only architects with a growing expertise in materials science and a desire to build green. Others have been experimenting with bricks made of, in part, cow’s blood and corn.

blood-bricks

Munro’s bricks are blood-red because, well…  (Source: Munro Studio)

The former sounds grisly, but proponent Jack Munro points to all the cattle claret that goes to waste—eight gallons per cow slaughtered for food. Munro mixed bovine blood with sand (after adding an antibacterial agent) and baked it at a mere 160 degrees for just an hour to produce bricks that he proposes as suitable for desert regions where mud bricks have long been common.

Still others are building with thatch and straw, suggesting that the past might inform a sustainable future.

Meanwhile, at Cambridge University in England, scientists at the Centre for Natural Material Innovation recently had a breakthrough in their quest to bioengineer, at the molecular level, a stronger form of wood. (We’ve covered the resurgence of wood in large-scale construction before and will come back to this topic soon.)

Cambridge University is also the professional home of Michelle Oyen, an expat from the American Midwest and a scientist who is bioengineering small samples of artificial bone and eggshell. She hopes that the process can someday be scaled up to create girders and beams of bone to construct skyscrapers.

Why bone? It’s a natural composite, made of protein and mineral. “The mineral confers stiffness and hardness, while the protein confers toughness and resistance to fracture,” Oyen wrote in The Conversation. “Although bones can break, it is relatively rare, and they have the benefit of being self-healing.” Bone is actually stronger than steel, measured per ounce, and it can last millions of years. (This is how we know about dinosaurs.)

Oyen doesn’t expect her technology to transform cities overnight, but buildings of “neo-bone,” as she calls it, might be part of the puzzle as humans strive to preserve our environment. “The science is still in its infancy,” she wrote, “but that doesn’t mean we can’t dream big.”

Today’s sci-fi, tomorrow’s Internet

Labs that grow bio-brick and neo-bone may strike some as the stuff of movies about the tinkering of wild-haired professors and bubbling flasks that burst into flames. And indeed, Ginger Dosier told a TEDx audience that bioMASON endured early trial and error. (“Bricks that I made three years ago,” she said, “are still wet.”)

But didn’t Apple and Ford Motors start out in garages? It may be that the funding boost from the DARPA program will take biomimetic technologies to the next level. After all, this is the agency that brought us tools we take for granted today, from the Internet and GPS to self-driving vehicles. (Okay, self-driving vehicles still seem like the future.) And as implied by the first word of the agency’s name, building sustainably might be a matter of national (and global) security. Stay tuned.

collagen

A sequence of collagen, a building block of bone, itself perhaps someday a building block of buildings! (Image by Jon Heras, Equinox Graphics)

This post was written by Suffolk Construction’s Content Writer Patrick L. Kennedy. If you have questions, Patrick can be reached at PKennedy@suffolk.com. You can connect with him on LinkedIn here or follow him on Twitter at @PK_Build_Smart.

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