human hair may someday lead to ultra-high resolution computer displays,

new biological sensors and even microscopic eyes.

Designed by scientists at Pennsylvania State University at University

Park the tiny carbon tubes are only one or two dozen nanometers

(billionths of a meter) in diameter. These microscopic "nanotubes" are

laced with iron-ruthenium crystals, which glow green when exposed to light.

The tubes are currently made using carbon-iron-ruthenium vapor heated

to 700 degrees C (1290 degrees F). When the gas mixture is deposited on

quartz, carbon nanotubes grow, some of which are wrapped inside each

other in multi-wall tubes. Nestled in the hollow cores of the nanotubes

are cubic crystals of the photoluminescent iron-ruthenium.

Lead researcher Beth Dickey explained that her team's next goal is to

make tubes that glow blue and red. "We can then pattern devices with the

three types of color pixels," she said in an interview with United Press

International. "And if that's the case, then we've got a really sexy

technology," added co-researcher Craig Grimes, Dickey's husband. "Right

now if you were to make a display device or an optical detector, you are

generally constrained to what you can make in the lab in terms of pixel

size and resolution. We now have the opportunity to make pixels smaller

and grow a new kind of display technology."

The scientists are confident that they can soon develop red- and

blue-glowing nanotubes using additives of rare earth elements such as

erbium and thulium.

"We're moving very quickly towards applications," Grimes said. "I

would say that in a year or so's time, we could make a red-blue-green

optical device."

Material physicist Apparao Rao at Clemson University in South

Carolina, whose team is conducting similar research, said another

possible way to get different colors using the same iron-ruthenium

crystals would be to grow them smaller in the tubes. The smaller the

crystals are, the more the electrons in them are confined, which means

the crystals become bluer.

Grimes suggested it might prove possible to use these tubes in

microscopic eyes, functioning similarly to how rod proteins work in the

human eye. "We are not there yet by any means, though," he said.

More immediate applications, Rao added, are biological and chemical

sensors that change luminescence whenever they capture key molecules.

The scientists are currently trying to boost the nanotubes' light

intensity by increasing their length. The average length of the tubes is

about 5 microns. They take roughly 20 minutes to grow and are about

one-twentieth the width of a human hair.

The researchers reported their findings in the journal Applied Physics Letters.

(Reported by Charles Choi in New York)