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).”
“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.
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.)
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. Continue Reading ›