Strange “Water Bears” Lead to Discovery of a New Glass Material

November 3, 2015 | Kelly Tatera

A tardigrade or water bear on top of a cotton swab
Photo credit: Darron Birgenheier/Flickr (CC BY 2.0)

Best known for their ability to survive the vacuum of space, tardigrades have now inspired the creation of a new type of glass that defies its typical structure.

Odd-looking, microscopic animals called tardigrades — or less scientifically known as “water bears” — live just about anywhere: in bubbling hot springs, moss and lichens, Antarctic ice... the list goes on. Impressively, they’ve even withstood the extreme cold and radiation of outer space. The little creatures are nearly invisible and indestructible, and they recently led scientists to the exciting discovery of a new glass material that could improve the efficiency of technologies like solar cells, optical fibers, and LED lights.

Juan de Pablo, a professor of molecular engineering at the University of Chicago, became fascinated with tardigrades after reading about how scientists could dry them out and then revive them years later with water. Thus, his 20-year exploration of the unusual properties of glass began with these unusual water bears.

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De Pablo explains that once the water is removed in the procedure, tardigrades rapidly coat themselves in glassy molecules. This process is what allows them to stay in a state of “suspended animation,” or a deathlike state without final termination.

The degree molecular order in the tardigrade’s glassy material shocked the researchers. “Randomness is almost the defining feature of glasses,” de Pablo said. “At least we used to think so.” In fact, by definition, glass has an amorphous structure, meaning the material is less rigidly defined than regular, crystalline solids. However, the new type of glass created by researchers at the University of Chicago and the University of Wisconsin-Madison has well-defined molecular organization, just like a crystal.

“What we have done is to demonstrate that one can create glasses where there is some well-defined organization,” says de Pablo. “And now that we understand the origin of such effects, we can try to control that organization by manipulating the way we prepare those glasses.”

The new glass material was produced through a method called “physical vapor deposition” — the molecules are evaporated in a vacuum and then left to condense on top of a temperature-controlled support structure. Then, the researchers analyzed the material by measuring the way light interacted with the glass, a technique called “spectroscopic ellipsometry.”

The finding that all or most of the molecules were aligned in the same direction was certainly unanticipated since most glasses have random molecular structures. However, lead study author Shakeel Dalal, a graduate student at the University of Wisconsin-Madison, says that molecularly-structured glass isn’t just hard to come by — it’s also extremely desirable.

Researchers who make things like solar cells and LED lights need materials with structured molecules because, if the molecules point in a certain direction, it’s easier to manipulate them to carry charges or emit light. Until now, researchers were unsure about what exactly caused the molecules in certain glasses to “cooperate” and point in the right direction — they assumed certain glass molecules were just better at organizing themselves than others. But this new study suggests otherwise.

During the previously explained process of “physical vapor deposition,” the temperature difference between the glass molecules and the temperature-controlled structure is what prompts the structured orientation of the new glass material. To expand on this discovery, de Pablo and researchers from several institutions in the United States and France conducted tests to see if this temperature finding held true, and it did.

Not only did de Pablo and fellow colleagues create a new glassy material inspired by the biology of the unique tardigrade, but this discovery will help others create structure-oriented glasses in the future. The efficiency of solar cells, optical fibers, LED lights and more will be revolutionized — all thanks to the microscopic, funny-looking water bears.

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