http://www.ieee-virtual-museum.org/exhibit/exhibit.php?taid=&id=159272&lid=1&seq=8&view=

What is Nanotechnology?

There’s a lot of buzz—nanotechnology is “coming soon.” But what is nanotechnology? Why doesn’t anyone ever explain that? Well, it’s not that easy. While experts agree about the size of nanotechnology—that it’s smaller than a nanometer (that’s one billionth of a meter) they disagree about what should be called nanotechnology and what should not. Looking back at the historical roots of nanotechnology helps us get a better grasp on what nanotechnology is and why it’s important now, and how it will change the world in the future.

Using technology developed to construct microchips, engineers can now construct microscopic machinery (like the gears shown in this electron microscope image, dwarfed by a mite). Future generations of nano-machinery promise to be even smaller. Source: Sandia National Laboratories.

The story of nanotechnology begins in the 1950s and 1960s, when most engineers were thinking big, not small. This was the era of big cars, big atomic bombs, big jets, and big plans for sending people into outer space. Huge skyscrapers, like the World Trade Center, (completed in 1970) were built in the major cities of the world. The world’s largest oil tankers, cruise ships, bridges, interstate highways, and electric power plants are all products of this era. Other researchers, however, focused on making things small. In the 1950s and 1960s the electronics industry began its ongoing love affair with making things smaller. The invention of the transistor in 1947 and the first integrated circuit (IC) in 1959 launched an era of electronics miniaturization. Somewhat ironically, it was these small devices that made large devices, like spaceships, possible. For the next few decades, as computing application and demand grew, transistors and ICs shrank, so that by the 1980s engineers already predicted a limit to this miniaturization and began looking for an entirely new approach.

As electronics engineers focused on making things smaller, engineers and scientists from an array of other fields turned their focus to small things—atoms and molecules. After successfully splitting the atom in the years before World War II, physicists struggled to understand more about the particles from which atoms are made, and the forces that bind them together. At the same time, chemists worked to combine atoms into new kinds of molecules, and had great success converting the complex molecules of petroleum into all sorts of useful plastics. Meanwhile geneticists discovered that genetic information is stored in our cells on long, complex molecules called DNA (about 2 meters of DNA is packed into each cell!) This and other work led to a greater understanding of molecules, which, by the 1980s, suggested entirely new lines of engineering research.

Physicist Richard Feynman.

So, the roots of nanotechnology lie in the merging of three lines of thinking—atomic physics, chemistry, and electronics. Only in the 1980s did this new field of study get a name—nanotechnology. This new name was popularized by physicist K. Eric Drexler, who pointed out that nanotechnology had been predicted much earlier, in an almost-forgotten 1959 lecture by Nobel Laureate Richard Feynman, who proposed the idea of building machines and mechanical devices out of individual atoms. The resulting machines would actually be artificial molecules, built atom by atom. While the resulting molecule might itself be larger than a nanometer, it was the idea of manipulating things at the atomic level that was the essence of nanotechnology. But not only was this kind of manipulation impossible at the time, but few people had any idea why it would be useful to do it! With all the new research, however, Drexler revived Feynman’s vision and helped introduce the general public to the basic concepts of nanotechnology.

Although nanotechnology dates from the 1950s, the biggest changes have occurred just in the past few years. In the late 1990s, research money began pouring in from corporate and government sources. In the space of just a few years governments around the world launched three major (and many other smaller) new research programs, including the National Nanotechnology Initiative in the U.S. and the nanotechnology branch of the European Research Area. Japan has its own huge nanotechnology program, with money coming from private industry and government agencies such as the Ministry of Trade and Industry.

Buckyballs, Nanotubes, DNA, and Micromachines: Building Blocks of Nanotech

Nanotechnology is a field that’s just being established, and although there are big plans for the smallest of technologies, right now, most of what nanotechnologists have accomplished falls into three categories: new materials—usually chemicals—made by assembling atoms in new ways; new tools to make those materials; and the beginnings of tiny molecular machines.

A buckyball. Source: Office of Basic Energy Science/U.S Dept. of Energy.

Some of the primary building blocks in nanotechnology are buckminsterfullerenes (almost always known as buckyballs or fullerenes), which are clumps of molecules that look like soccer balls. In 1984 Richard Smalley, Robert Curl, and Harold Kroto were investigating an amazing molecule consisting of 60 linked atoms of carbon. Smalley worked these atoms into shapes he called “fullerenes,” a name based on architect Buckminster Fuller’s “geodesic” domes of the 1930s and first suggested by Japan’s Eiji Osawa. Sumio Iijima, Smalley, and others found similar structures in the form of tubes, and found that fullerenes had unique chemical and electrical properties. Fullerenes became nanotech’s first major new material. But what to do with them? Engineers turned their attention to finding some practical use for these interesting molecules.

The letters “IBM” spelled in xenon atoms, as imaged by the atomic force microscope. Courtesy: IBM.

While engineers thought about practical uses for fullerenes another discovery in search of an application was being made. In 1981 Gerd Karl Binnig and Heinrich Rohrer invented the scanning tunneling microscope or STM, which has a tiny tip so sensitive that it can in effect “feel” the surface of a single atom. It then sends information about the surface to a computer that reconstructs an image of the atomic surface on a display screen. If that weren’t amazing enough, a little later, researchers discovered that the tip of the STM could actually move atoms around, and Donald Eigler and a team at IBM staged a dramatic demonstration of this new ability, spelling out "IBM". Researchers believed they had a tool, the atomic force microscope (AFM), that could build things atom-by-atom. But, like the discovery of fullerenes, it remained to be seen if anything useful could actually be built this way.

The development of tools such as AFMs coincided with the introduction of very powerful new computers and software that scientists could use to simulate and visualize chemical reactions or “build” virtual atoms and molecules. This was especially useful for scientists working with complex chemical molecules, particularly DNA. Researchers recognized that the actions of DNA resembled some of the things nanotechnologists were now calling for—the use of molecules to construct other molecules, the self-replication of molecules, and the use of molecule-size mechanical devices. Perhaps DNA (or its cousin, RNA) could be modified to create the first nanomachines?

Ned Seeman has succeeded in manipulating strands of DNA into customized molecules with multiple interconnections. He believes this is the first step in doing more complex things with DNA, such as using it to create molecular machinery. Source: NYU.

Geneticists had already found ways to use DNA taken from bacteria to make a nano-scale replicator used for scientific research. By modifying some of the chemical reactions that take place in natural DNA, genetic engineers had figured out a way to make copies of nearly any DNA molecule they wanted to study. But with the computers and tools available to them by the 1990s, they began using DNA or DNA-like molecules to do other things—like construct new chemicals or tiny machines. Many researchers began investigating ways to make proteins—the components from which DNA is made—that would perform useful tasks, such as interacting with other materials or living cells to create new materials or perhaps attack diseases. One of the first breakthroughs was Professor Nadrian Seeman’s demonstration of a tiny “robot arm” made from modified DNA. While the arm could not yet really do anything useful, it did demonstrate the concept.

An experimental MEMS micro-gyroscope developed at the Georgia Institute of Technology.

Meanwhile, electronics researchers approached nanotechnology from another direction. Since 1959, engineers had etched and coated silicon chips using a variety of processes to make integrated circuits (ICs). The transistors and other chip elements reached nano-scale in the late 1990s. They also used these same techniques to develop the first micromachines—microscopic devices with actual moving parts. Some of the early versions of these were simply intended to demonstrate the process without doing anything particularly useful, such as a tiny guitar with a string that could be plucked using an atomic force microscope. But in the late 1980s these began to be commercialized as machines-on-a-chip, or micro-electrco-mechanical systems (MEMs), which combine ICs and tiny mechanical elements. However useful MEMs are, most engineers feel that the techniques used to make ordinary ICs will never be refined enough to make true nanotechnologies. For that reason, engineers are now concentrating on discovering entirely new ways to make ICs, building them from the ground up rather than cutting and etching “bulk” silicon slices.

With the appearance of protein-based chemistry and other techniques in the 1990s, researchers began looking both for practical uses for nanotechnology and new ways to make nano-molecules or micromachines. A different but related problem was that of making nanomolecules in large numbers. A single nanomachine or nanocircuit for example, would not be able to do enough work to make a difference in the real world—thousands or millions might be needed. Engineers needed ways to turn out their nanomachines in huge numbers, and so they began looking for a way to make a nano-scale machine or molecule that would assemble other nano-scale machines or molecules. K. Eric Drexler called it a “self assembler,” and scientists believe that it will be one of the keys to making certain kinds of nanotechnology useful and practical. To date, very few practical nanotechnologies and no self-assemblers have been used outside the laboratory.

Nanotechnology in Today’s World

Nanotechnology is a science in its infancy, but that doesn’t mean it hasn’t been put to use. What exactly has been accomplished in nanotechnology so far? In general, all of today’s practical nanotechnologies are those using nano-size particles of various materials, or nanometer-size features on integrated circuits (ICs), rather than the complex molecular machines that engineers first envisioned. These current nanotechnologies are still made by “top down” methods (like those used in conventional chemistry and IC manufacturing), rather than the largely unproven “bottom up” techniques predicted by nanotechnology’s boosters.

IBM's millipede memory chip. Courtesy of IBM Zurich Research Laboratory. Unauthorized use not permitted.

Many current nanotechnologies, for example, consist of the ever-shrinking transistors, interconnecting wires, and other features on digital ICs. As of 2005, some integrated circuits now have transistors that measure about 50 nanometers across—well inside the accepted size-based definition of nanotechnology. But chips are still made using advanced versions of the lithographic processes developed in the 1950s, which layer on materials and then carve away at them to form the electronic circuits. They are not, in other words, constructed molecule-by-molecule from the bottom up. However, chip manufacturers point out that when working with extremely small circuit elements, the behavior of electrons changes, so entirely new principles are at work. Also, there is at least one new chip with a somewhat different claim to being “nanotechnological.” This is IBM’s “Millipede” memory chip, which draws its inspiration directly from the Atomic Force Microscope (AFM). Electronics manufacturers can also point to the latest generation of high-density computer hard drives, which have extremely thin coatings of just a few atoms’ thickness applied to the surface of the disc by a process called chemical vapor deposition.

While such nanochips are beginning to appear in greater numbers, most of us more often encounter applications of nanotechnological materials that are made in “bulk” form and added to other products. By far the best known of these are the controversial “nanotechnology” trousers introduced by The Gap and Eddie Bauer stores in 2005. These were simply ordinary cotton pants, treated with nanoparticles of a new, stain-resistant chemical that attached itself to the cotton molecules.

Different types of carbon nanotubes. Source: NASA.

Carbon nanotubes, which can now be made in large quantities at relatively low cost by companies like Hyperion Catalysis International Inc., are being incorporated into a wide range of other products. Because the fibers conduct electricity very well, Hyperion was able to mix them into plastic compounds, which auto makers can then mold into parts that conduct electricity. This is useful for preventing static electricity charges from building up on parts such as plastic fuel system components, where the static can eventually damage them or, in some cases, cause a spark. Nanotubes mixed into plastics are very strong and light, and have been used to make car body components, tennis rackets, and other items. They have also been used to improve battery performance, and may some day be used in other technologies that traditionally used ordinary carbon or metals to conduct charges. Infineon Technologies in Germany, for example, has demonstrated the use of the tubes to connect components on microchips. In 2002 they showed how nanotubes could be used to replace ordinary metal wires allowing them to carry more current but taking up less space. That would result in computer chips that can pack more circuits into less space; one of the longstanding goals of chip designers.

Researchers such as Xiaohu Gao of the University of Washington are finding ways to introduce quantum dots into the body. Rats are injected with the dots, which find their way to cancer cells. If such cells are present, the cancers can be pinpointed by medical imaging technology, as shown here. Source: Xiaohu Gao , University of Washington.

One very useful new material is the semiconductor quantum dot. While not used in electronic circuits, quantum dots are nonetheless made from the same silicon used in computer chips. These tiny bits of material are coming into widespread use in experimental biology and, in a limited way, in medical diagnosis. The dots can be coated with certain chemicals, which are specially formulated so that they bind themselves to particular things—such as RNA, cell walls, or other types of molecules found in cells. One interesting application of this technology is its use in analyzing DNA material taken from the body. These DNA “scanners,” first introduced commercially by Matsushita Corporation, combine integrated circuit technology and quantum dots to analyze genetic material much more rapidly than was possible before, and may lead to more rapid assessment of diseases. A second use of coated quantum dots is injecting them into the body, where they circulate until they come in contact with whatever type of cell their coating is designed to attach itself to. Then when a powerful infrared light source is shone on the body, it penetrates the flesh, illuminates the massed quantum dots, and the reflections can be detected to provide a “live” picture of an organ, muscle, cancerous growth, or other internal part without the need for surgery. Unfortunately, not all of these quantum dots are suitable for injection into a living human body, and some are even poisonous, but bioengineers are working around that problem.

Even with these real-world applications, the current uses of nanotechnology (other than nano-size particles of various materials) remain very limited. In fact, several once-promising nanotechnology based systems introduced commercially in the 1990s did not meet with success, such as the nanotube–based Field Emission Displays proposed as competitors to other flat-panel information displays. However, researchers are rapidly making progress toward what some think of as true nanotechnologies—self-assembling, molecule size machines to perform all sorts of tasks (including manufacturing the nano-size materials made by other methods today). The nanotechnological future, we are told, is right around the corner.

The Future of Nanotech

Artist's rendition of the space elevator of the future. Source: IEEE Spectrum, Aug 2005

The future of nanotechnology is largely a question mark. Futurists say we are entering a new era, somewhat like the Industrial Revolution of the 18th and 19th centuries. That revolution changed nearly everything about the way people lived. But no one at that time could have predicted how those changes would unfold. Could we be on the brink of another very rapid period of profound technological and social change?

The nanotechnological revolution, if it occurs, will be just as unpredictable in the long-term, but scientists and engineers have laid out some pretty fantastic forecasts for the near-future. For example, some see great promise for the use of nanotubes in super-strong materials. Even though the plastic composites made today using relatively short nanotubes are not yet much stronger than earlier types of composites, long nanotubes are expected to be used for extraordinary applications like the proposed “space elevator.” This system would replace rockets for the transport of payloads and people into earth orbit.

The structure of a complex dendrimer created at the University of Michigan. The molecule carries folate molecules that target cancer cells and molecules of a drug to treat the cancer. Source: Michigan Nanotechnology Institute for Medicine and the Biological Sciences.

Another major area where nanotechnologists predict stunning changes is in medicine. Imagine a world where no one gets seriously ill, grows older, or even dies (until they want to). That is what the prophets of nanotechnology say is in store for the 21st century. Today’s nanotechnologies used in medicine offer only modest benefits, such as the ability to target diseased or cancerous cells, making them easier to locate.

In the near future, engineers tell us, that will change. Tiny molecular machines, perhaps based on complex, branched molecules called “dendrimers” will be injected into the body not only to locate cancers but also to find and repair cells damaged by disease or aging. Livers and hearts damaged by natural wear-and-tear, inherited diseases, poor nutrition, or alcoholism will be fixed or even replaced. Genetically based ailments such as Alzheimer’s will be cured by replacing the faulty genes.

NanoInk Corporation believes that its “Nscriptor” system for producing nanoscale structures will be a stepping stone to future nanomanufacutring. Source: NanoInk.

Some futurists have predicted that the most profound changes will be the result of the introduction of molecular assembly “factories,” perahps even small small enough to fit on a desktop. These would, some say, make it possible for virtually anyone to design and build virtually anything, using nanorobots or perhaps a new technology called “nanoink,” created by NanoInk founder Chad Mirkin. Nanotechnology researchers like K. Eric Drexler and Ralph Merkle say that this could be done by imitating and improving upon the “manufacturing” that DNA accomplishes inside the body.

In 1999, researchers such as Nadrian Seeman at New York University demonstrated the principle of using modified DNA molecules to build a tinymachine, and somewhat later Nanoink founder Chad Mirkin had demonstrated building up nanostructures by depositing layers of materials on a substrate.

These and other experiments have also led researchers to believe that they will eventually be able to assemble circuits atom-by-atom in order to create the next generation of computer chips. The circuits on these chips will be much smaller than what is currently possible, and will enable the building of much more powerful computers. What difference will that make? Some, like engineer Raymond Kurzweil, think that computers will have personalities and be as smart as humans within 20 years. We may even be able to “download” our own personalities into computers, to become virtual humans. With nearly unlimited computing power, programmers are sure they could create software that completely blows away anything possible today.

Not surprising, these amazing predictions have inspired fear as well as wonder. Environmentalists and others point out that nanotechnology may bring with it unexpected dangers. The nanomaterials being made today, like fullerenes, are often in the form of extremely small particles. Even when these particles are made from common materials like carbon, they may interact with the human body or the environment in ways that are unlike those of natural particles of the same materials. Some say that allowing nanoparticles to be included in products ingested or applied to the body may pose health risks for consumers.

Others predict that nanotechnology may get out of control, causing a huge man-made disaster. Eric Drexler and others, such as computer engineer Bill Joy of Sun Microsystems, warned in 2000 that self-replicating machines might run amok if they escape into the environment, competing with natural bacteria, plants, and people for natural resources. Then, in 2002 the public’s awareness of nanotechnology—the bad side of nanotechnology—was greatly expanded when author Michael Crichton published his best-selling novel Prey, about tiny, self-duplicating nanorobots that band together to try to take over the world.

Whether public fears are founded in fact, it is true that the future of nanotechnology has inspired as much caution as optimism. Recently, in response to public outcry, researchers such as Dr. Vicky Colvin of Rice University have begun evaluating the risks and rewards of current nanotechnologies. Colvin and other engineers believe that, with wisdom, they can bring the wonders of nanotechnology into being while avoiding the pitfalls.