Image: Silk and resonator
Tufts University
A square stenciled with gold resonators is attached to a swirl of silk. Material that incorporates dielectric silk as well as the resonators can become "invisible" to specific terahertz wavelengths. researchers say.
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updated 8/11/2010 10:34:24 AM ET 2010-08-11T14:34:24

For thousands of years people have worn shimmering silk to stand out in a crowd. Within the next few years people could wear silk to become invisible in a a crowd.

For the first time ever, scientists have created an invisibility cloak made from silk, and coated in gold.

The new metamaterial, as invisibility cloaks and their kin are technically called, only works on relatively long terahertz waves (a region of the electromagnetic spectrum between radio and infrared light), but the Boston-area scientists who developed the technology think that silk could work as an invisibility cloak at much smaller wavelengths, even in the visible range.

The research could lead to a wide range of optically unique materials for use in biomedicine or defense.

"This is an unusual angle for a metamaterial because of silk's ability to interface with the human body," something that no other metamaterial is currently capable of, said Fiorenzo Omenetto, a scientist at Tufts University who, along with colleagues at Boston University, helped develop the silk-based metamaterial and detail their new research in the journal Advanced Materials.

"On the sensing side it gives you a platform that is very adaptable."

Invisibility cloaks, along with their optically exotic cousins, perfect absorbers and perfect reflectors and others, belong to a special class of materials known as metamaterials. Unlike most materials, which derive optical properties like color from their chemical make up, metamaterials derive their properties from the physical structure.

A curly cue, or short spiral, is a common  metamaterial structure. Scientists call them split ring resonators, or SSRs. Usually scrawled into metals, SSR can give ordinary materials extraordinary abilities, like absorbing or reflecting all the specific wavelengths of light, or bending a wavelength around an object.

To create their silk-based metamaterial, the Tufts and Boston University scientists, including Richard Averitt, started with a one-centimeter-square piece of silkworm silk. (In another recent paper, Omenetto's colleague and another co-author of the Advanced Material's paper, David Kaplan of Tufts, created silk-producing bacteria.) Onto that tiny piece of dielectric silk they stenciled 10,000 gold resonators.

Ordinarily when silk is exposed to terahertz waves they pass straight through it. When the new silk metamaterial was subjected to T-rays the scientists detected a resonance.

A metamaterial that works in the terahertz range is nothing new. But, unlike other metamaterials, silk is biocompatable — the human body won't reject silk-based implants the way it does with most other materials. The scientists implanted the patterned silk into a muscle, and still detected a resonance.

The new silk research is "interesting," said Douglas Werner, a metamaterial scientist at Pennsylvania State University. "There is a lot of interest in using flexible substrates for metamaterials, and silk is a good candidate for that."

The potential applications of silk-based invisibility are huge. Omenetto and his colleagues at Tufts aren't even focused on Harry Potter or Star Trek-style invisibility materials, although he says that is one potential application.

Their main focus is in biomedical applications. One of the first biomedical uses could be as an implantable glucose sensor for diabetics. As the level of glucose changes inside the body, it changes the silk. Then as the silk changes, do does the metamaterial printed on the silk. That change would then be relayed to the person's cell phone; no needle prick necessary.

Silk-based invisibility would also allow doctors and radiologists to cloak various organs or tissues and see through them, said Omenetto, getting a better image of the organs or tissues usually hidden behind.

© 2012 Discovery Channel

Explainer: The 2010 Weird Science Awards

  • Atala et al., PNAS / WFUBMC
    A researcher injects cells from a rabbit's penile erectile tissue into a scaffold (top photo), a procedure which results in a functional rabbit penis (bottom photo).

    That's one small step for rabbit penises, and potentially one giant hop for restorative surgery. An experiment that gave rabbits lab-grown penises capable of fathering offspring won the most votes in msnbc.com's 2010 Weird Science Awards contest. Cells of penile tissue were grown on scaffolds of cartilage. When the creations took on the right shape, they were grafted onto rabbits that had their penises removed. After the transplants, the rabbits were able to breed ... like rabbits. The procedure could someday be used to heal humans as well. The photos at right show an experimenter working on the penile tissue, and an X-ray image of the restored penis.

    Click "Next" to see the nine other Weird award-winners for 2009-2010, and click on the highlighted links to learn more.

  • Fruit bats get kinky

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    Researchers report that female Chinese fruit bats use oral sex to prolong the pleasure for their partners. The study suggests that there may be an evolutionary advantage to at least some types of kinky sex in the animal world. But can you imagine being the researcher with the job of watching bat porn?

  • Is the future trying to avert our doom?

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    Why did it take so long to get the world's most powerful particle-smasher up and running? Two scientists suggested it might be because the Large Hadron Collider was about to create phenomena so catastrophic that the future sent a cosmos-altering signal back in time to disrupt its operation. The research wasn't taken all that seriously when it came out, and since then the LHC was restarted without incident.

  • Octopus builds mobile home

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    It sounds like a spin-off from "The Little Mermaid" or "Spongebob Squarepants": An octopus builds a mobile home under the sea by stacking up coconut shells. It moves in ... and then it carries the whole heap across the seafloor. "It was an extremely comical sight," said marine biologist Julian Finn, who spotted the behavior off the Indonesian coast. "I never laughed so hard underwater." Let's just hope those clever cephalopods don't develop opposable thumbs. That won't be such a laughing matter.

  • Researchers clone dogs that glow

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    Seoul National University  /  AP

    Awww, how cute! South Korean scientists cloned a litter of genetically engineered dogs that glow red under ultraviolet light. Like an earlier experiment involving glowing cats, this isn't aimed at creating glow-in-the-dark pets. Rather, it's a proof of concept for procedures that could help develop treatments for genetic diseases in humans. If you can add the coding to make fluorescent protein, maybe you can add the coding to fix a genetic flaw.

  • Gay penguins make good dads

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    German zookeepers in Bremerhaven had a problem on their hands when penguin parents rejected one of their eggs. To solve it, they placed the egg in a nest shared by two male penguins. The pair is one of three same-sex couples that have tried to mate at the zoo. The males incubated the egg for 30 days and continued to care for the chick after it hatched. Homosexual behavior has been documented in many animal species. "Sex and coupling in our world don't always have something to do with reproduction," the zoo said.

    Video: Msnbc.com's Dara Brown reports on the gay penguin parents.

  • Huge blob lies deep beneath Nevada

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    You wouldn't know it by driving through the Great Basin in Nevada, but researchers have detected a huge blob of highly compressed rock that is dripping like honey, extending from a depth of about 47 miles to at least 310 miles beneath the surface. The blob is 30 to 60 miles across, scientists say. But don't worry, Nevadans: This blob isn't expected to cause earthquakes - or rise up and destroy Las Vegas.

  • Nude 'Mona Lisa' surfaces

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    Art historians have long suspected Leonardo da Vinci painted more than one version of his famous "Mona Lisa," and now a painting with much more Mona has surfaced. The painting, which portrays its subject nude from the waist up, had been hidden for almost a century within the wooden walls of a French cardinal's library. Experts are looking into whether this particular work, now on display in the Tuscan town of Vinci, was actually painted by the master.

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    Was that any way to treat a genius? Back in 1737, Galileo Galilei's admirers removed three fingers, a vertebra and a tooth from the astronomer's body when his corpse was being moved to a new tomb. The vertebra and one of the fingers were recovered soon afterward, but the whereabouts of the tooth and the other two fingers were a mystery. Recently, however, the relics turned up in a container that was auctioned off to a private collector. Now the Galilean body parts, including the finger shown at right, will be put on display at the Museum of the History of Science in Florence.

  • Fragrances pay tribute to dead celebs' DNA

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    Let's get one thing straight: MyDNAFragrance's "Antiquity" line of perfumery will not make you smell like Marilyn Monroe did when she was alive, and certainly not like her mortal remains. Rather, the "Marilyn" fragrance is mixed up from ingredients that are coded to capture the "essence" of the movie star's mitochondrial DNA. Other scents pay tribute to Albert Einstein, Joan Crawford, Katharine Hepburn, Michael Jackson and Elvis Presley. The company behind the scents says the process is "very scientific," but others might well conclude that the whole exercise smells like a gimmick.

    Click here for the 2009 Weird Science Awards

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