The Dallas Morning News

DALLAS – Scientists from the University of Texas at Dallas have spun yards of chemical ribbons that are lighter than a feather but stronger than steel – a significant advance in the rapidly growing field of nanotechnology.

The development could lead to a host of high-tech applications that scientists have dreamed of but haven’t had an easy way to create: futuristic clothes that light up, store energy or blunt bullets; car doors that are ultra light and extra strong and double as batteries to store solar energy; flexible, filmy light bulbs that are thinner than a human hair; artificial muscles for robots; and solar sails to propel space vehicles.

A report describing the chemical ribbons, created from tiny carbon tubes barely visible to the human eye, appears in Friday’s issue of the journal Science.

“This is a big deal, a real big deal,” James Tour, a chemist at Rice University in Houston, said of the new study. “Every paragraph is a gold mine.”

The ribbons are created from carbon nanotubes, filaments about one-five-thousandth the width of a human hair. At the atomic level, the nanotubes look like cylinders of chicken wire. Because the nanotubes, like diamonds, are made entirely of carbon, they are extraordinarily strong. They also conduct electricity.

Scientists had known of carbon nanotubes’ exceptional properties but had struggled to easily convert them into convenient forms. Last year, the UTD scientists, led by chemist Ray Baughman, spun the nanotubes into yarn. Other scientists had created small sheets of nanotubes, but their process was cumbersome.

“The value of this invention is to make it into sheets,” said Ned Thomas, a materials scientist at the Institute for Soldier Nanotechnologies at the Massachusetts Institute of Technology in Cambridge. “Clever people will take those sheets and put them into technologies that have yet to be invented.”

Making the ribbons is quite simple, Baughman said. The UTD scientists started with a “forest” of nanotube trees, about one-third of a millimeter high. Then they stuck a Post-It note to one edge of the forest and gently pulled away. The nanotube trees were drawn out, and as the researchers kept pulling, the trees stuck to each other side by side, forming a long, wispy and transparent sheet.

Sheets more than a meter long, about two inches wide, and less than one-thousandth the width of a human hair thick can be pulled in less than a minute, by hand in the lab, Baughman said. The process easily could be industrialized, he said.

“There is no limit on how wide they can be,” Baughman said.

The ability to convert carbon nanotubes into such a useful form will be a boon to many small companies trying to use them to create newer or better devices, Thomas said.

“Nanotechnology needs this,” he said. “It’s been hyped, and there’s been a lot of expectations.”

Baughman, who said the university and a collaborating Australian national lab have filed a provisional patent application to cover the technology, rattled off a slew of ideas, many with military applications.

“You would like to have blankets that could be unfurled in the desert to harvest energy for soldiers,” he said. The nanotube sheets, unlike other materials that collect solar energy, still collect electricity when bent or creased.

Clothing made of cross-woven nanotube ribbons could make strong yet light protective gear, possibly even strong enough to repel a bullet.

The scientists have already shown that one of the nanotube sheets, sandwiched between two pieces of Plexiglas and microwaved, can weld the Plexiglas together. Transparent devices, such as a car window, could be created this way with a nanotube-based antenna or heating element inside.

The nanotube sheets could also be used as electrodes for light-emitting displays, such as those found on clock radios.

Engineers have also dreamed of ultra-lightweight sails for space travel. Light from the sun could push on these sails, powering space vehicles.

Such a sheet, Baughman said, has to maintain the stress of light pushing on it but can’t be too heavy. A sail measuring about one-third of a square mile would weigh only 66 pounds.

“How do you make sheets that are thin enough and strong enough?” Baughman said. “These carbon nanotube sheets seem to fit the bill.”

Some tweaking of the nanotube sheet technology is still needed, Baughman said. The sheets created so far are made of multi-walled nanotubes, tubes nested inside each other like Russian dolls. Single-walled nanotubes, which are harder to grow as forests, are more desirable for some applications, such as conducting electricity. But there’s no reason to doubt they could be pulled into sheets, Baughman said.

The UTD researchers, along with researchers at Texas Scottish Rite Hospital in Children in Dallas, are exploring whether the nanotube sheets could be useful in medicine. Mario Romero, a neurobiologist at Scottish Rite, said he’s found that several types of cells can grow on the sheets. The sheets could be useful for measuring electrical and chemical properties of cells, or possibly in tissue engineering.

Other scientists who participated in the research were UTD’s Mei Zhang, Shaoli Fang, Anvar Zakhidov, Sergey Lee, Ali Aliev and Christopher Williams. Ken Atkinson from a national laboratory in Victoria, Australia, also contributed.

(c) 2005, The Dallas Morning News.

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