Smaller Than You Think

Here are a few facts that may help you begin to understand how small a nanometer is:

• The size of a nanometer compared to a meter is like the size of a marble compared to the earth.

• A human hair is about 50,000 nanometers in diameter.

• Five carbon atoms in a row fill a distance of one nanometer.

Are you having trouble imagining a nanometer? If you are, don't feel bad. You aren't alone.

A billion—the number of nanometers in a meter—is a very big number. A billion is approximately three times the population of the United States. It's the approximate number of letters in 6,000 books of 500 pages each. A billion seconds is about 32 years. A billion is the number of dollars the U. S. government spent on research and development related to nanotechnology in 2005.

Don Eigler, the nanotechnology pioneer who first arranged xenon atoms to spell out IBM, regularly works at the nanometer scale and has a gut-level feel for how atoms behave. But even Don Eigler admits that he has a hard time imagining a nanometer in relation to a meter.

Imagining one part in ten is easy, Eigler says, since most people have ten fingers. Imagining one part in one hundred is manageable. Most people can even imagine one part in a thousand: If you have to take a thousand steps to get somewhere, you can imagine that. But larger numbers are a problem.

“Suppose I said, 'Take a hundred million steps. Where do you end up?' ” Eigler asked. “We don't have a feel for that number. I can't imagine what a hundred million of anything in a row is like. It's just too big.”

There are a million nanometers in a millimeter and a billion nanometers in a meter. Those numbers are very difficult—maybe impossible—for most of us to imagine.  

To talk about nanotechnology, we need to talk about the nanoscale world, where objects are measured in nanometers. But don't worry if you can't imagine a nanometer. Though size is the distinguishing feature of the nanoscale world, it isn't what makes this world so interesting to researchers.

Small Is Different

Nanotechnology generally deals with objects having dimensions of between one and one hundred nanometers. One reason these tiny objects are interesting is that they obey a different set of rules than the ones you and I are used to. We live at a size scale where certain physical laws apply—the laws of classical mechanics observed by Isaac Newton in the seventeenth century.

But Newton's laws no longer apply when you are dealing with nanoparticles, chunks of matter with dimensions of less than one hundred nanometers. At the nanoscale, quantum mechanics—the modern physical theory that deals with the structure and behavior of subatomic particles—comes into play. Because of quantum mechanics, nanoparticles don't act like bigger lumps of the same stuff—they look and act differently. A few atoms together in a nanoparticle just don't behave the same way they do when there are millions of atoms together.

When you're dealing with nanoparticles, the ratio of surface to volume is huge. Suppose you have a fist-sized lump of gold. The atoms at the surface of the lump are small compared to all the atoms in the lump. But if you broke that lump of gold down into gold nanoparticles, the ratio of surface to volume changes. In a cluster of 100 atoms, more than half the atoms are on the surface. The properties of a nanoparticle are really governed by surface effects.

How does that change the way matter behaves? Once again, consider that fist-sized chunk of gold. It looks gold in color and it melts at around 1948 degrees Fahrenheit (1064 degrees Celsius).

This image shows cubes of magnesium oxide. Nanoscale particles of gold were deposited on the crystal faces to help define the surface topography. [more]

Compare that to particles of gold that are between one and one hundred nanometers across. These particles melt when heated to just a few hundred degrees Fahrenheit. These particles can look red, blue, or a variety of other colors, depending on the particles' sizes and distance from each other.

The ancient Romans knew how to color glass by adding gold. Initially the glass is colorless, but it becomes ruby-red when heated in a controlled fashion. The Romans knew how to make the glass turn red, but they didn't know that the color came from nanoparticles of gold.

Butterfly Wings and Gecko Toes

A close examination of the natural world has revealed examples of how conditions at the nanoscale affect what happens at the human scale.

Take, for example, the blue morpho butterfly. This butterfly's wings are a beautiful, shimmering blue, a color so bright that naturalists have reported seeing the flash of blue wings from a quarter of a mile away. You might think that such a vibrant color comes from blue pigment—but there is no blue pigment in the butterfly's wings. In fact, microscopic studies have shown that the butterfly's wing is covered with tightly packed rows of clear scales. No color at all!

These clear scales form layers that reflect blue light. Each layer is 62 nanometers thick and the layers are 207 nanometers apart. This spacing is exactly what's needed to reflect that shimmering blue light. Spacing of other distances will reflect light of other colors. The interaction of light with these nanoscale structures creates the brilliant blue color of the butterfly's wings.

Nanoscale hairs on the toes of a gecko help this lizard climb walls.

Another natural example of how very small structures have very big effects can be found on the feet of geckos, lizards noted for their ability to run across walls and ceilings, sticking effortlessly to the slickest surface. On the bottom of each gecko foot are half a million microscopic hairs, each about one-tenth the diameter of a human hair. The end of each hair splits into hundreds of even tinier hairs, measuring just 200 nanometers across. When a gecko presses its foot down, these tiny hairs unfurl, pressing very closely against the surface.

When atoms or molecules are brought very close together, they are weakly attracted to each other. The attractive forces, known as van der Waals forces, operate at the nanoscale so we don't usually notice them. But these forces, multiplied by the millions of hairs on the gecko's feet, hold the lizard to the ceiling quite securely.

The nanoscale characteristics of butterfly wings and gecko toes have inspired researchers to contemplate commercial products that make use of the same principles. Researchers at Manchester University's Centre for Mesoscience and Nanotechnology in the United Kingdom have developed what they call "gecko tape," a supersticky reattachable dry adhesive that uses synthetic hairs mimicking those on the gecko's feet. Researchers at cosmetic manufacturer L'Oréal are working to produce cosmetics that reflect brilliantly colored light like the blue morpho butterfly's wings.

It's Happening Now

Gecko tape and blue morpho makeup aren't on the market just yet. Many reports on nanotechnology focus on future possibilities, describing how nanotechnology could change the world. Those possibilities are certainly interesting to contemplate. But perhaps more interesting are the ways that nanotechnology has already affected our lives.

Take, for example, the gas in your car. That gas was extracted from crude or unprocessed oil, the stuff that comes out of the ground—and nanotechnology has made a big difference to how much gasoline is extracted from every barrel of oil.

Crude oil is a mixture of hundreds of different hydrocarbons, compounds made of hydrogen and carbon. When crude oil is refined, large hydrocarbon molecules are broken into smaller ones in a process called cracking. How much gasoline can be extracted from a barrel of crude oil depends on the efficiency of the cracking process.

Back in 1962, researchers at Mobil dramatically increased the efficiency of the cracking process, upping the quantity of gasoline extracted from a barrel of oil by a whopping 40 percent. They accomplished this revolutionary change in petroleum refining with a porous crystal called zeolite. Riddled with openings small enough to distinguish among molecules of different sizes and shapes, zeolite acts as a catalyst, an additive that accelerates and increases the efficiency of a chemical reaction. (Those zeolite crystals qualify as nanotechnology because the holes that riddle them are tiny—less than a nanometer across in some cases.) According to a 1992 National Academy of Sciences estimate, the shift to a zeolite catalyst saves the United States more than 400 million barrels per year of oil.

That change in 1962 didn't make the newspaper headlines. It was a change in an industrial process—not something to get worked up about. It wasn't called "nanotechnology" back then, but that's what it's called now.

Mobil's use of zeolite can be said to be one of the first broad-scale applications of nanotechnology. It's an example of what Mark and Daniel Ratner, authors of Nanotechnology—A Gentle Introduction to the Next Big Idea, call “stealth nanotechnology.” That's nanotechnology that's hidden in other products, nanotechnology that we, as consumers, don't even notice, though it stealthily makes a difference in our lives.

Carbon Nanotubes and Hockey Sticks

The products of nanotechnology seem to inspire superlatives: super small, supersticky for gecko tape, or, in the case of carbon nanotubes, super strong.

Carbon has different forms, the best known of which are graphite, a soft substance made of layers of carbon, and diamond, an extremely hard substance made of carbon atoms joined in a rigid crystal. In 1985, three scientists discovered the buckminsterfullerene molecule, also known as a buckyball or fullerene. This previously unknown form of carbon is an arrangement of 60 carbon atoms in a spherical structure. The discoverers' of the fullerene thought the geometry of the spherical arrangement of atoms resembled a geodesic dome and named the molecule after the dome's inventor, R. Buckminster Fuller. Others have compared the fullerene to a soccer ball.

Following the discovery of the fullerene, researchers worldwide were inspired to look for other forms of carbon. In 1991, Japanese scientist Sumio Iijima discovered the carbon nanotube.

This is a scanning electron microscope image of nanowires. Each rod in the image is about 50 nanometers wide.

Carbon nanotubes are ridiculously strong (much stronger than steel), light, and flexible. NASA is very interested in using them to create lighter and stronger spacecraft. Nanotubes have already been put to work in aircraft, lightweight bicycle frames, super-strong hockey sticks, and other sporting equipment. They may also be used to make car bodies stronger and lighter, contributing to fuel economy.

In some situations, carbon nanotubes can also be "sticky" like gecko toes. There aren't many things that can be both strong and adhesive; this is another example of how nanoscale structures are different from larger-scale materials.

But even more interesting than the strength of carbon nanotubes is their electrical conductivity. They may be the perfect material for making tiny electrical circuits, since electricity passes through them with very little resistance. In 2002, researchers succeeded in making nanotube transistors. At IBM, researchers used a single nanotube to create a working computer circuit. Since each nanotube is basically one large molecule, they created a circuit using a single molecule.

Perhaps you've heard of Moore's Law. In 1965, Intel co-founder Gordon Moore predicted that computer processing power, or the number of transistors on an integrated chip, would double every 18 months. This prediction became known as Moore's Law, and so far, it's held true. In 1965, a single chip held 30 transistors. Six years later, Intel introduced its first chip, which held 2,000 transistors. Today's chips have 400 million transistors.

As chipmakers pack more chips into less space, we get faster computing and greater data storage—at a lower price. In 1968, you paid about a dollar for a single transistor; today you pay a dollar for 4 million transistors.

But there's a limit to how many transistors can be packed onto a silicon chip. Researchers are looking to carbon nanotubes to come in when the features on silicon chips just can't be made any smaller.

Smart Materials

One of the first nanotechnology products to hit the consumer market with great fanfare was one that seems rather trivial: stain-resistant trousers, sometimes known as nanopants. (You can learn more about the nanopants in our nanohome.) But the fabric of those nanopants is an example of a very active area of nanotechnology research—the development of "smart materials."

GORE-TEX® fabric has holes that are just a little larger than 100 nanometers—big enough to let water vapor escape, but small enough to keep liquid water out.

A smart material is designed to accomplish specific tasks. Another example of a smart material is a fabric called GORE-TEX ® . It contains a waterproof sheet that's pierced with holes that are just a little larger than 100 nanometers. These holes are big enough to let water vapor escape (so your sweat isn't trapped), but small enough to keep liquid water out (so you stay dry).

Some smart materials change in response to outside stimuli, like the lenses of eyeglasses that darken in sunlight or the mugs that change color when filled with hot coffee. Today, materials are being transformed at the nanoscale to make them smart in brand new ways. For example, w ork is underway on dynamic armor that firms up at the sound of a bullet, or transforms into an instant splint. This is only the beginning.

Now and the Future

It's tough to write an article about nanotechnology that doesn't come across as a laundry list of possibilities. Nanotechnology has great potential in the field of medicine, materials science, and electronics. Products currently on the market include cosmetics, sunscreen, water filters, solar panels, stain-resistant fabrics, and bread containing nanocapsules of nutrients. (To learn more in depth about these products, visit our NanoHome. For a more complete list of products that make use of nanotechnologies, see the Project on Emerging Nanotechnologies' nanotechnology consumer products inventory . The varied products on the consumer products list have one thing in common: they have all emerged from a new way of examining and manipulating the world.

It's difficult to spot the beginning of a technological revolution. If you had been at London's Great International Exhibition in 1862, you might have seen some objects made of a moldable material called Parkesine, the first synthetic plastic. No one who saw those samples predicted the uses to which plastics would later be put. Creation of the first integrated circuit in 1958 set off developments in the electronics industry that led to the modern information revolution. But back in 1958, no one would have predicted the cell phone, the laptop computer, the Gameboy, and the many other electronic devices that dominate our lives.

Like these earlier technological changes, nanotechnology has the potential to spark revolutionary changes in how people live their lives. This article describes just a few of the applications of nanotechnology that are currently being explored in laboratories worldwide. Talk to researchers, and for every application named here you'll get a hundred more. They won't all come to fruition, but even if one in a thousand does, the world will be a different place.