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Nano-Suit Protects Bugs From Space-Like Vacuums

15 April 2013 3:10 pm
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Put a fruit fly larva in a spacelike vacuum, and the results aren't pretty. Within a matter of minutes, the animal will collapse into a crinkled, lifeless husk. Now, researchers have found a way to protect the bugs: Bombard them with electrons, which form a "nano-suit" around their bodies. The advance could help scientists take high-resolution photographs of tiny living organisms. It also suggests a new way that creatures could survive the harsh conditions of outer space and may even lead to new space travel technology for humans.

Naked and dying. A northern house mosquito larva without a nano-suit dehydrates to death in a scanning electron microscope vacuum.
Credit: Yasuharu Takaku et al.

Snapping a picture with a nanometer-level resolution of the proboscis or muscle cells of a fruit fly isn't easy—in fact, it's deadly. Scientists have to use a scanning electron microscope, which must peer at objects in a vacuum because air molecules absorb the electrons that the microscope depends on to take the picture. Only a tiny number of creatures, such as the famously hardy tardigrade, can survive the process. Most other bugs die quickly of dehydration as the vacuum sucks the water out of their bodies.

A fruit fly larva is one such victim. But when Takahiko Hariyama of the Hamamatsu University School of Medicine in Japan and his colleagues placed the millimeter-sized larva in a scanning electron microscope and fired electrons at it, they found that the young fly wiggled in place for an hour as if everything was fine. When they put another larva in the same vacuum and let it sit there for an hour before bombarding it with the microscope's electrons, it predictably dehydrated to death. Somehow, the electron stream was keeping the larva alive and so unscathed that it later grew to become a healthy fruit fly.

The scientists then used the microscope to peer closely at the edge of the insects' skin. They found that the energy from the electrons changed the thin film on the larvae's skin, causing its molecules to link together—a process called polymerization. The result was a layer—only 50- to 100-billionths of a meter thick—that was flexible enough to allow the larva to move, but solid enough to keep its gasses and liquids from escaping. "Even if we touched the surface [of the layer]," Hariyama says, "the surface did not break by our mechanical touch." It was almost like a miniature spacesuit.

The team dubbed the layers "nano-suits." Most insects do not have natural layers on their surfaces that become nano-suits when exposed to an electron stream, however. So Hariyama and colleagues decided to create artificial nano-suits. They dunked mosquito larvae in a pool of water mixed with a chemical called Tween 20, which is useful because it's not toxic and is commonly found in detergents, cosmetics, and hard candy. The researchers then showered each larva in plasma, so that the Tween 20 would polymerize and become a nano-suit, and moved the nano-suited larvae to the microscope's vacuum to watch what happened.

Mosquito larvae wearing the artificial nano-suit could handle the vacuum for about 30 minutes, the team reports online today in the Proceedings of the Natural Academy of Sciences. Mosquito larvae without the nano-suits died swiftly and horribly, as expected. "Within a few minutes, they were dehydrated," Hariyama says. "They're very sad experiments." The researchers repeated the experiment with other insects, including flatworms, ants, and sand hoppers, and the manmade nano-suit protected them all.

The finding is "exciting," says astrobiologist Lynn Rothschild of NASA's Ames Research Center in Moffett Field, California, who was not involved in the work, because it indicates that nano-suited creatures might survive travel by a meteorite or comet through the extreme environments of space. She notes that it could also have applications for space travel. "Imagine a flexible space shield, roughly the diameter of a human hair that could protect against dehydration and radiation."

Suited up. A healthy, nano-suited northern house mosquito larva wiggles in a scanning electron microscope vacuum.
Credit: Yasuharu Takaku et al.

Hariyama hopes that the nano-suits will lead to the ability to create videos of the tiniest insect organs while they're in motion. Because the environment inside the microscope is so deadly, scientists can't normally create close-up videos of living insects. But the vacuum is not the only problem: As the resolution of the microscope climbs, so does the electron radiation, and that radiation can also harm and kill the insects. The team is now trying to create a new nano-suit using chemicals other than Tween 20 to protect insects from both the vacuum and radiation.

Experimental physicist Athene Donald of the University of Cambridge in the United Kingdom, who was not involved in the research, says that although the experiment is clever, it's still far from providing close-up videos of living insect organs in action. "They're working at really very low magnifications so they can see the whole organism," she says, "If they want to look at any specific bit, they will have a real problem."

"It's quite an ingenious set of conditions they've come up with," says microscopist Jeremy Skepper, also of Cambridge and not involved with the work. Skepper says that it's "amazing" that insects were able to withstand the nano-suiting process well enough to grow out of the larva stage afterward, although he agreed that radiation from the electron current is still a major issue. "It's the equivalent of you or I sunbathing naked on the top of Everest under a hole in the ozone."

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