Sheets of plastic made by E. coli can fold into whatever shape you desire. Astronauts on long missions might one day rely on such bacterial origami to make tools on the go.
On a spacecraft, every inch of storage space is precious, says astrobiologist Lynn Rothschild of NASA’s Ames Research Center. There’s a strict limit to how much you can fit in a launch vehicle.
“You can’t take up an infinite amount of volume,” Rothschild says, which will be an especially big problem when astronauts head to distant destinations like Mars. “Everything you have at launch means something else can’t come with you.”
One way to save room is to pack flat plastic sheets to be folded later. Waiting to manufacture the plastic until you’re already at your destination would be even better.
To this end, Rothschild and her team have genetically engineered strains of E. coli that can create plastic, which in turn can fold itself into 3D shapes when heated. They presented their plastic creations at the end of September at the International Genetically Engineered Machine competition in Boston.
“Biology has the advantage of being self-replicating and self-repairing,” says Rothschild. “You could in theory bring up a tiny amount of material and have it live off the land. Then you’ve solved the upmass problem.”
Raid the cafeteria
The work started with plastic tableware taken from the NASA cafeteria. The team practised folding take-out containers and utensils under heat lamps to see what kind of plastic would work best. Eventually, they settled on two types: polystyrene and the polymer P(3HB). The former was best for folding, while the other won points for being biodegradable.
Next, they figured out how to genetically engineer strains of E. coli to produce each type of plastic in the lab, and processed the P(3HB) into flat sheets.
To fold the plastic, the team drew lines on it with black ink on the areas that needed to bend. Placed under infrared light, the darker segments absorb heat more quickly, leading it to contract faster than the rest.
The team also explored an organic approach to folding. Bacillus spores were attached to thin strips of cellulose “tape”, also grown in the lab, and placed strategically on the plastic. The spores expand and contract in response to humidity, bending the plastic in different directions as they move.
In the end, the team successfully folded simple structures including a box (top picture) and a cup (second picture). But in future, they envision creating more complicated items: solar sails, perhaps, or origami habitats.
“Once you have the ability to do a valley fold and a mountain fold, you can combine them to create really intricate structures,” says Tyler Devlin at Brown University in Rhode Island, a member of the team. “If you give this technology to some who knows how to create intricate 3D objects from a flat sheet, they can go on to do some really useful and cool things.”
It’s a promising idea, says Olivier de Weck, who studies space logistics at MIT. Any proposal that could save mass and volume on the vehicle is on the right track. If the plastic can be manufactured and folded without taking up too much of the astronauts’ valuable time, that’s an added bonus.
However, he adds, any scheme that involves bringing bacteria aboard the spacecraft introduces potential problems. What happens, for example, if the E. coli gets into astronauts’ food supply? “There’s no such thing as a free lunch,” he says.
(Image: Stanford-Brown iGEM Team)
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