In realm of the tiny, newfangled 'nanotech' knows no boundaries

Monday, October 30th 2000, 12:00 am
By: News On 6

By Alexandra Witze / The Dallas Morning News

Even Eric Clapton couldn't play the new Craighead guitar.

It requires not a slow hand, but a small hand. Really small. The guitar is only the size of a human blood cell.

Its creator, Harold Craighead of Cornell University, never wanted to compete with Fender Stratocasters. He built the miniature guitar as a testament to scientific ingenuity.

These days, more and more scientists are expressing themselves by shrinking their work, like a flutist switching to the piccolo. They create Lilliputian versions of everyday items.

Yet these are no ordinary objects. They are technological wonders of the nanoworld.

There's the "nanotruck," crafted from a single molecule, with protective bumpers and tie-down points for hauling cargo. There's the telescoping coil of carbon atoms that slides back and forth like a miniature spring. And there's the itty-bitty abacus, keeping count as molecules slide across its bars.

One day, no one may blink at such marvels. Nanotechnology – the science and art of building wee wonders, atom by atom – will soon permeate modern life, says Don Eigler, a physicist at IBM's Almaden Research Center in San Jose, Calif. Electronics, automobiles and medicines could all benefit.

"When that happens," Dr. Eigler says, "people will look back and say that the most exciting time was right now."

Twenty years ago, Generation M, or Micro, took the first tentative steps into Lilliput, the land of miniature people in Gulliver's Travels. Engineers worked on the scale of a micrometer, or millionth of a meter, to create tiny electronic and mechanical devices. Generation M scientists learned how to transform a slice of silicon into a powerful computer chip, and how to design miniature sensors to inflate air bags during a car crash.

Now it's time for Generation N. N stands for nanometer, the billionth-of-a-meter length that is smaller than the smallest virus. In the nanoworld, individual atoms and molecules serve as Lego-like building blocks for tiny equipment.

Teeny truck

The nanotruck, for instance, is made of a single molecule.

Its creator, James Tour of Rice University, admits it won't win any trucking contests against Dodge or Ford. Its bed is just a few nanometers long.

But it's big enough to load up a small molecule and take it for a ride. And the truck should get great mileage; rather than burning gas or diesel, it's propelled by electric fields.

So far, the truck is still a low-rider, since its inventors haven't figured out how to put wheels on it. Eventually, its ground clearance will be a scant quarter of a nanometer.

Monster-truck fans shouldn't scoff. Rice chemist Vicki Colvin cites a line from the movie Men in Black:

"What is it with humans and size anyway? Just because something is very, very small doesn't mean that it can't be important."

The nanoguitar

Like the miniature guitar. In part, it's a whimsical tribute to what scientists can do with good lab equipment. Its six strings each measure 50 nanometers wide, roughly the diameter of 100 medium-size atoms side by side. Its body is made of crystalline silicon – usually the material of computer chips rather than a handcrafted instrument.

Dr. Craighead and his student, Dustin Carr, peppered the silicon with a high-voltage beam of electrons, which traced out the guitar's body. A chemical wash then sculpted the instrument in three dimensions.

The same technology, Dr. Craighead says, can be used to build intricately detailed silicon structures for basic research. So, in a way, the guitar could lead to better fiberoptic communications, sensors or electronics.

Such work can also be a political instrument. This summer, Cornell scientists, working in the same laboratory, fashioned the world's smallest saxophone as a gift to President Clinton.

They carved 287,900 pictures of a saxophone – each measuring just 6 by 8 micrometers – onto a silicon chip. Together, the pictures delineated a silhouette of President Clinton playing his own saxophone. The gift was supposed to underline the importance of investing in basic scientific research.

Itty-bitty abacus

But no one has yet checked George W. Bush's counting skills, or Al Gore's "fuzzy math," on the world's smallest abacus.

Researchers built the machine in 1996 at IBM's research lab in Zurich, Switzerland. They planted 10 buckyballs – soccer-ball-shaped molecules of pure carbon – in each groove on a copper surface. Then the researchers nudged the buckyballs with the pointy tip of a special microscope. (If the buckyballs had been the size of softballs, the tip would have been bigger than the Eiffel Tower.)

Repelled by the monstrous tip, the buckyballs scooted back and forth along the grooves like beads on a nano-sized string. The abacus worked as well as a normal-sized one in a schoolroom.

Buckyballs once enjoyed the nanoworld spotlight, even being named Molecule of the Year in 1991 by Science magazine. But they haven't gotten any starring roles in consumer projects.

Lately, their upstart cousins, buckytubes, have gotten top billing. (Both are named after R. Buckminster Fuller, the architect whose geodesic domes resemble the soccer-ball shape of a buckyball's 60 carbon atoms.)

Utility players

Buckytubes, more commonly known as nanotubes, are also made of pure carbon. They look like nothing more than a nanometers-wide roll of chicken wire. But they do much more.

The amazing nanotube can conduct electricity or insulate from it; be filled with hydrogen gas or other possible fuels; act as miniature wires for futuristic computers; and lend their flexible strength to other materials.

And this summer, scientists at the University of California, Berkeley, found yet another use: as springs or bearings for nano-sized machines.

Graduate student John Cumings peeled the tips off some nanotubes that were nested inside one another like Russian dolls. He found that the tubes telescope inside each other with almost no friction. So they might act as miniature springs, without the friction problem that heats up springs in ordinary devices.

The nanotubes also acted as miniature bearings when rotated around each other, the Berkeley team reported in Science.

But a nanotube's usefulness can depend on how it is made. This month, scientists at the Georgia Institute of Technology reported that buckytubes created different ways have dramatically different properties.

Scientists make nanotubes mainly through two methods. In one, researchers zap a piece of graphite with electricity and let the carbon atoms rearrange themselves into tubes. The other method relies on a chemical meltdown to restructure the atoms.

The chemical method usually makes the tubes weaker. The Georgia team discovered a way to bend individual tubes and test the dramatic differences in strength.

For some applications, like reinforcing other materials, weak nanotubes aren't a big problem. In fact, the flaws might help the tubes interlock with each other, thus staying put inside the material, the scientists will report in an upcoming issue of Applied Physics Letters. But only perfect nanotubes will do for electronics.

For other applications, no kind of nanotube will work. So scientists are devising new ways to put nanomaterials together.

Nanoshell games

At Rice, engineer Naomi Halas works on nano-sized versions of malted milk balls: tiny spheres of silica coated with a metal. These "nanoshells," though, are less likely to end up in the candy aisle of the grocery store than on drugstore shelves or the cosmetics counter.

For instance, Dr. Halas wants to stuff the nanoshells with medicine, then put them into sick people where they could target a tumor. Her team is developing a heat-sensitive type of plastic; when implanted beneath skin and zapped with a laser, it might soften and release drug-laden nanoshells into a particular part of the body. The shells, if coated with a biologically friendly material, could then dissolve and release their medicine.

Or nanoshells could help color a new wave of cosmetics. Color is determined by how a material reflects or absorbs different wavelengths of light; that, in turn, is determined by the material's structure at the nanometer scale. Nano-sized particles of gold, for instance, stain cathedral glass a stunning red.

"Things that make color are all, in principle, nano," Dr. Halas says.

Embedded in a computer screen, nanoshells might allow the display to change colors or become transparent. Mixed with glass or plastic, nanoshells could create smart windows that know when to darken to save energy. Added to cosmetics, they might help create different hues.

A golden touch

At Southern Methodist University in Dallas, chemists John St. John and Patty Wisian-Neilson work with the equivalent of a lemon drop: a solid nanoparticle.

Drs. St. John and Wisian-Neilson have figured out a way to spread nano-sized blobs of gold through a type of plastic. It sounds like a waste of valuable gold, but the work could be useful in electronics or biomedicine, Dr. St. John says. A fine mist of nanoparticles, spread throughout the plastic, could carry electric current in a computer chip or a medical-imaging device.

This is the first time anyone has gotten gold particles to stabilize in an inorganic plastic, the researchers reported in August at a meeting of the American Chemical Society. Just knowing how to manipulate the tiny blobs may help scientists discover better materials, Dr. St. John says.

Surprise, surprise

But nobody knows what surprises these materials may offer. Many discoveries happened when scientists were expecting something else.

At Rice, Dr. Colvin's group was tossing around ideas on how to build a better battery. They ended up making a "metal sponge" – a thin film that looks like brilliantly colored aluminum foil and might be used in sensors or chemical catalysis.

At Georgia Tech, physicist Uzi Landman found that theoretical "nanojets" spewing out propane don't work the same as a Coleman stove's fuel line. The tiny golden nozzle spurts out the liquid in unexpected directions – an important result if researchers start working with other liquids at the nanoscale.

At Sandia National Laboratories in Albuquerque, Jeff Brinker found that he could zap a material with ultraviolet light and adjust the size of nanoscale pores. The work could help separate air's combination of oxygen and nitrogen molecules, which differ in size by only 0.02 nanometers. Industry has long sought a cheap and easy way to separate the two gases, instead of producing them through more laborious means.

From guitars to metal sponges, nanoresearch can claim "an extraordinary set of discoveries," says Mihail Roco, a nanotechnology expert at the National Science Foundation.

And whether the findings come serendipitously, or after years of hard work, they have all contributed to a fundamental breakthrough in how scientists view the world.

"Now we have the moment," says Dr. Roco. "Now we understand the basics of matter."