Do the potential dangers of nanotechnology to society outweigh the potential benefits?



Viewpoint: Yes, from unforeseen pollution to deliberately designed weapons of mass destruction, nanotechnology holds significant risks, and the legal, technical, and cultural work that must be done to tip the balance toward safety is not being conducted.

Viewpoint: No, nanotechnology research contributions to advanced electronics and medical progress far outweigh any perceived danger.

Everything we see around us is made of atoms, often combined together in molecules of particular chemical compounds. For example, a molecule of water consists of two hydrogen atoms and an oxygen atom. When we deal with materials in our ordinary lives, we handle many billions of molecules at a time. This limits the precision and versatility with which we can manipulate the matter around us.

Nanotechnology is a word used to describe techniques by which we can work with matter on the atomic or molecular scale. Experts predict that it will have a major impact on our lives by about 2015. In the United States the National Nanotechnology Initiative is funding research and training in the field, and other industrialized nations are establishing programs in nanotechnology as well.

The potential applications of nanotechnology are boundless, although medicine and electronics manufacturing are areas of particular interest. Advocates predict that nanotechnology systems will allow us to cure diseases by directly repairing the intricate biochemical mechanisms and structures in human cells, or to clean up the environment by removing toxins, molecule by molecule. Others warn that nanotechnology could be used by terrorists to construct undetectable weapons, or launch microscopic machines that run amok and process the entire biosphere into "gray goo."

Nanotechnology implies the ability to select and manipulate individual molecules and atoms, to repair a defective structure or build one from scratch. So nanotechnologists are working on molecular-scale tools to go where ordinary tools can not. One promising area of research and development involves carbon nanotubes, cage-like molecules consisting of 60 or more carbon atoms forming a narrow cylinder. The nanotubes can be used as microscopic probes or as tools for manufacturing miniaturized electronic devices. Nanotechnology must also rely on robotics to scale down human movements to the submicroscopic level.

Perhaps the most controversial area of research in nanotechnology is self-replication. If nanotechnology systems could be engineered to build copies of themselves, they would be much less expensive to produce in large numbers. However, allowing the self-replication of tiny robotic devices intended, for example, to modify the environment or the workings of the human body, is a scenario viewed with trepidation by many. The thought of combining this ability with artificial intelligence advances such as machine learning raises fears of an invisible army of devices evolving to pursue their own agenda, out of our control and probably to our detriment.

Like most powerful tools, nanotechnology can be a double-edged sword. It can be used for good or for evil, and may have consequences unintended by those who deploy it. Attempting to legislate against knowledge is, in general, neither helpful nor effective. Therefore, as with other technologies in the past and present, our role must be to understand what we have made, and try our best to ensure that it is used wisely.

—SHERRI CHASIN CALVO

Viewpoint: Yes, from unforeseen pollution to deliberately designed weapons of mass destruction, nanotechnology holds significant risks, and the legal, technical, and cultural work that must be done to tip the balance toward safety is not being conducted.

Against the background of the many promises of nanotechnology, there is a strong and legitimate concern about the potential dangers of this new capability. The true power of nanotechnology is unproven, but with claims ranging from self-assembling nanobots to sky hook elevators into space, the potential for both good and harm exist with this new technology. Can we handle all this power? Do we have the social frameworks and technical understanding and skills to deal with both the direct and indirect effects of nanotechnology? History suggests that we do not.

The power to heal is also the power to harm. Technology has always been a two-edged sword. It may actually be easier to design a nanobot to target healthy cells than to attack cancer cells. One can imagine a new age of weapons, specifically designed to avoid the body's defenses. Similarly, nanodevices, aimed at removing toxins and restoring the environment, could be refashioned to destroy crops or selectively cause environmental damage within an enemy's territory. Unlike biological warfare, which is indiscriminate and can turn on the aggressor, nanodevices could be programmed to work within boundaries and to self-destruct when their jobs were completed.

Monofilaments, if manufacturable, might become essential building blocks for a sky hook and open up space exploration. They could also be used to make nearly invisible, gruesome weapons. Finer than a spider web but as strong as steel, these incredibly thin polymers could slice through almost any materials, making vandalism, breaking and entering, and even murder easier.

Of course, the most celebrated and remarkable promise is the promise of immortality. The flip side of this promise is the risk of extinction itself. Indeed, nightmare scenarios of the entire biosphere being transformed into "gray goo" of nanodevices have become an object of serious discussion.

Dangers of Nanotechnology

Recognition of the two-edged nature of nanotechnology is not new. It dates back to at least to 1986, with the publication of Engines of Creation , a largely upbeat view of nanotechnology. More recently, Bill Joy, one of the pioneers of computer technology, has raised concerns about the dangers of nanotechnology, most notably in an article in Wired magazine. Although the risks of nanotechnology have been expressed in many fashions over the years, they can be viewed in four distinct ways: nanotechnology puts powerful means of destruction into the hands of irresponsible people; the unknowns of nanotechnology threaten us with pollution and other unintended consequences; nanotechnology can take away our humanity; and nanotechnology contains the seeds of mass extinction.

Nanotechnology puts powerful means of destruction into the hands of irresponsible people. Among the promises of nanotechnology is the ability to manufacture sophisticated devices at extremely low costs. Much of this is predicated upon the ability of nanodevices to create nanodevices, either through the use of specialized assemblers or via self-replication. This could put exquisitely designed weapons into the hands of individuals, terrorists, and rogue nations. Both known weaponry, such as chemical weapons, and unimagined nanoweapons could become available. With current weapons of mass destruction, testing, obtaining exotic precursors, and specific evidence, such as radioactivity, make monitoring and control possible in many instances. In contrast, nanoweapons, by definition, very small and made from common materials, would be almost undetectable.

Many people have the ability to create computer viruses, with over 1,000 new ones created each year. In fact, it's even possible for teenagers with low levels of skill (so-called "script kiddies") to copy code and vandalize sites. The combined forces of government and industry have not stopped the creation of new viruses, and there have been numerous instances in our connected world of the quick and destructive spread of these damaging programs. If such capability were extended to the world in general (a not unlikely event given the pervasiveness of networks and smart devices, combined with significant availability of assemblers), the results could be tragic. Even if this technology doesn't become available to the individual, it's likely to be available to many nations. It is not unreasonable to project a significant probability of a costly and risky arms race based on nanotechnology.

Advances in nanotechnology are driven almost entirely by curiosity and economics, with little concern for precedents that might be set and the establishment of both moral guidelines and inherent security. This means that it is left to chance who will become the first mover for significant advances, such as the development of assemblers, and how much safety will be built into these devices.

There is not even good agreement on when the different advances are likely to take place. In fact, discussions tend to smear out options and possibilities. Speculation about using nanobots to clean the blood stream are likely to be made in the same conversation with predictions of sky hooks and advanced computer components.

Going further, there may be even greater challenges if nanotechnology is hybridized in any way with other technologies. No technology exists in isolation, and the combination of nanotechnology and genetic engineering, or nanotechnology and robotics, could result in even more danger.

Unintended Consequences of Nanotechnology

The unknowns of nanotechnology threaten us with pollution and other unintended consequences. Physically, nanodevices have the potential for being persistent, like plastics, and invasive (because of their small size). One could easily imagine a worse problem than was seen with DDT in the environment, with nanomaterials lasting for a thousand years after taking up residence in the tiniest niches of living things. For specific nanomaterials, there may be consequences along the lines of what was discovered with "chemically inert" chlorofluorocarbons, which turned out to catalyze the destruction of the ozone layer. Heat pollution is an unavoidable side effect of the activity of nanodevices. In fact, one defense suggested against a gray goo surprise is simply to look for the heat signature of replicating devices.

There's an old phrase in computing, "It's not a bug, it's a feature." Bad design raises the risks of unintended consequences. Often designs are done in piecemeal fashion or without regard to the users and the environment. This sort of engineering approach could have devastating consequences when the actualization of the design lies in the real world rather than in cyberspace. Even a good design could easily be extended beyond the originator's intent. This has been seen in the use of combination drugs for weight loss, with deadly results. In addition, genetic engineering has already witnessed this, when corn not intended for human consumption made its way into the general market, causing allergic reactions among sensitive individuals.

The risk of unintended consequences rises steeply in the face of greater capability of nanodevices. If the devices have the ability to replicate, their effect will be similarly amplified. If they are modular, that is, they can be combined with other nanodevices to form more complex devices, predicting how they might interact with the users and the environment becomes much more difficult. If the devices are purposely evolved rather than designed, a practice that is already in evidence in the world of software, then it will become impossible to understand the details of the nanodevices or to predict their effects on the environment. The likelihood and the danger of evolved nanodevices devices will go up significantly if it is proven that evolved software has an economic advantage.

This scenario, again, only gets worse if nanotechnology is used in combination with other powerful technologies.

Nanotechnology: Danger to Humanity

Nanotechnology can take away our humanity. Inexpensive, invisible, powerful devices threaten freedom and privacy if they fall into the wrong hands. A totalitarian regime could use nanodevices to coerce its citizens. In the short term, it could monitor them pervasively with tiny sensors or threaten them with nanoweapons. It the long-term, modifying the populace with nanosurgery or even using nanobots to transform the genes of future citizens is not inconceivable. With nanodevices to do the work, large sectors of the population could be selectively destroyed, and intervention by other nations could be discouraged by threats based on expertise in nanotechnology.

A more subtle threat is that represented by the cyborg. Taking nanodevices into our bodies, either to extend our powers or to extend our lives, creates an intimate relationship between our machines and ourselves. Whether the result is viewed as symbiotic or parasitic, at some point, the needs, values, and orientation of these new individuals may become drastically different from what is currently defined as human. To some, this is an opportunity to revel in, but there is by no means a consensus as to whether this is good for our species or not. The social consequences could be profound: Are unmodified humans obsolete (and possibly expendable)? As people become cyborgs, are they still part of our community with all the same rights? How would the accumulation of power and wealth by "immortals" be handled? How are benefits distributed? Who is responsible for the costs of side effects? Philosophically, if all natural parts are replaced by nanodevices, and the resulting individual passes the Turing test, do you still have a human? Is it a good thing for the species if all humans are replaced this way, or is it an empty fantasy that ends humanity?

Nanotechnology Harbors Seeds of Mass Extinction

Nanotechnology contains the seeds of mass extinction. In 1974, leading scientists in the field of genetic engineering called for a moratorium on certain areas of research. In 1975, the Asilomar agreement went into effect, and scientists voluntarily suspended their work until the consequences were explored, rules were written, and remedies were found. No such agreement has been made among leading nanotechnologists.

Experience and Funding

Is the threat of nanotechnology less obvious or less real than what the genetic engineers faced? This is unlikely. Genetic engineering had its Andromeda Strain concerns just as the gray goo haunts nanotechnology (and both had and have their healthy skeptics). In 1975, genetic engineering was still in its infancy, with cloning, embryo research, "Frankenfood," and gene therapy still many years in the future. The primitive state of the art of nanotechnology doesn't explain the lack of attention devoted to its potential dangers. There are, however, two key differences between nanotechnology and earlier technological advances: the experiences of the scientists and the funding of their research.

Asilomar was an offshoot of the Pugwash conferences, where scientists took on the tough issues of living with nuclear weapons. The threat of nuclear annihilation was more vivid in the polarized Cold War years. Testing, proliferation, and safety problems were both urgent and intractable. Scientists were at the center of nuclear debates and were asked to make policy recommendations. Many also felt guilty about developing the Bomb and not opposing its use in Japan. Although the issues of living with nuclear weapons haven't gone away, they have faded—and almost no nanotechnologists have personal experience with building weapons of mass destruction.

While funding for genetic engineering was largely in the hands of government, specifically the National Institutes of Health (NIH), nanotechnology gets much of its funding from industry. Its pressures are market pressures, and competition encourages speed and applicability over deliberation and understanding. A nanotechnologist who advocates a pause in the development of nanotechnology would not only be challenging the current market ethos but taking on the corporation that funds his or her work.

Nanotechnologists are not restrained by their experiences and are driven by their funders to put nanodevices into the real world. In this context, it seems unlikely that precautions like secrecy, testing, and isolation of nanodevices will be taken. It is probable that nanodevices will not be engineered for safety with features such as traceability, self-destruction, and dependency. All this makes abuse more likely and error more probable. The consequences can range from vandalism to the infamous gray goo.

The power of nanotechnology is not intrinsically bad, but its destructive potential is great. The legal, technical, and cultural work that must be done to tip the balance toward safety is not being conducted. Laws are needed to control information, proscribe areas of activity, and control use and distribution. We must, as a species, develop a cultural response to this power that includes education, discussion, and approaches toward agreement and consensus. Timing is everything. Unlike our experience with nuclear weapons, we still have the time to be thoughtful, to prepare. But today, with work on safety still in front of us, we face a dangerous future. If Bill Joy is correct, that future is less than 30 years away.

—PETER ANDREWS

Viewpoint: No, nanotechnology research contributions to advanced electronics and medical progress far outweigh any perceived danger.

Birth of Nanotechnology

To make a rational argument, pro or con, one should examine both sides of a question, including the background for the debate. There was not even a word "nanotechnology" in 1959 when sometimes-jester Richard Feynman (Nobel Laureate in 1965) presented his classic lecture at the California Institute of Technology inspiring his audience with a view of a working world so small that all of the world's books could be stored on something the size of a dust speck. In a speech titled "There's Plenty of Room at the Bottom," Feynman said, "A biological system can be extremely small. Many of the cells are very tiny, but they are active; they manufacture substances; they walk around; they wiggle; and they do all kinds of marvelous things—all on a very small scale. Also, they store information. Consider the possibility that we too can make a thing so small which does what we want—that we can manufacture an object that maneuvers at that level."

Feynman said, "I am not inventing anti-gravity, which is possible someday only if laws are not what we think. I am telling you what could be done if the laws are what we think; we are not doing it simply because we haven't gotten around to it." Feynman's speech is viewed as the beginning of nanotechnology. He stressed better tools were needed. Feynman spoke of using big tools to make smaller tools suitable for making yet smaller tools, and so on, until researchers had tools sized just right for directly manipulating atoms and molecules.

Feynman did not envision the controversy his ideas would produce when researchers began speculating on the prospect that what these tiny devices would manufacture is copies of themselves, over and over and over at tremendous speeds; that these nanorobots could replicate. Another scientist, Bill Joy, co-founder of Sun Microsystems, published his essay titled "Why the future doesn't need us" in the April 2000 issue of Wired. Bill Joy wrote, "From the moment I became involved in the creation of new technologies, their ethical dimensions have concerned me, but it was only in the autumn of 1998 that I became anxiously aware of how great are the dangers facing us in the 21st century." After considerable rationalization, he added, "Thus we have the possibility not just of weapons of mass destruction but of knowledge-enabled mass destruction, this destructiveness hugely amplified by the power of self replication."

The Gray Goo Problem

Joy's essay popularized, and was based on, the 1986 book by K. Eric Drexler, Engines of Destruction: The Coming Era of Nanotechnology in which he said, "The early transistorized computers soon beat the most advanced vacuum-tube computers because they were based on superior devices.For the same reason, early assembler-based replicators could beat the most advanced modern organisms. "Plants" with "leaves" no more efficient than today's solar cells could out-compete real plants, crowding the biosphere with an inedible foliage. Tough, omnivorous "bacteria" could out-compete real bacteria: they could spread like blowing pollen, replicate swiftly, and reduce the biosphere to dust in a matter of days. Dangerous replicators could easily be too tough, small, and rapidly spreading to stop—at least if we made no preparation. We have trouble enough controlling viruses and fruit flies.

"Among the cognoscenti of nanotechnology, this threat has become known as the 'gray goo problem.' Though masses of uncontrolled replicators need not be gray or gooey, the term 'gray goo' emphasizes that replicators able to obliterate life might be less inspiring than a single species of crabgrass. They might be 'superior' in an evolutionary sense, but this need not make them valuable." He adds, "We have evolved to love a world rich in living things, ideas, and diversity, so there is no reason to value gray goo merely because it could spread. Indeed, if we prevent it we will thereby prove our evolutionary superiority."

The gray goo threat makes one thing perfectly clear: we cannot afford certain kinds of accidents with replicating assemblers. The gray-goo part especially continues to attract a lot of attention from science fiction fans, and some from the media.

What happened between Feynman's speech and Joy's essay were many discoveries and technological breakthroughs that have led to several Nobel Prizes for their scientific merit and value to humanity, and new fields like nanomedicine with untold promise for breakthroughs in treatments of cancer, diabetes, and other high profile diseases. Clearly there is much support for the view that any potential dangers of nanotechnology to society do not outweigh the potential benefits.

There have also been knowledgeable reports published to refute the gray-goo concept. Robert A. Freitas Jr., research scientist with Zyvex, wrote in 2000 on Some Limits to Global Ecophagy by Biovorous Nanoreplicators, with Public Policy Recommendations. He sees a potential danger, but puts it in perspective. Freitas concludes, "All ecophagic scenarios examined appear to permit early detection by vigilant monitoring, thus enabling rapid deployment of effective defensive instrumentation." Although there are some who propose outlawing certain research activities they deem dangerous, others point out the lack of success in such political measures throughout history, giving biological warfare agents and nuclear proliferation as examples. Cloning of humans can be added to the list.

Zyvex is a unique startup company. It was specifically founded to build what they call the assembler, the key tool to creating atomically precise materials and machines. As the researchers at Zyvex envision it, the assembler would start with a generic feedstock such as methanol and manufacture any precisely defined object which can be built from stable arrangements of the feedstock atoms. The assembler would start with the atoms and build up, an ultimate goal of many researches in nanotechnology. One team at Zyvex believes that they will eventually build a devices that can build smaller versions of themselves, which will then build smaller versions, and so on down to the nano world, but all this is as yet in the future.

Feynman was very positive. He said, "I am not afraid to consider the final question as to whether, ultimately—in the great future—we can arrange the atoms the way we want; the very atoms, all the way down!" The future got closer in 1981 when Gerard Binning and Heinrich Rohrer at IBM's Research Center in Switzerland invented a scanning tunneling microscope (STM), a tool that has become a workhorse in nanotechnology. The inventors of the STM received the Nobel Prize in 1986 for making it possible for researchers to finally see atomic and molecular surfaces. Advances have come steadily since. Richard Smalley, and collegues, at Rice University received the Chemistry Nobel Prize in 1996 for discovering fullerenes, which led to the discovery of carbon nanotubes by Japanese scientist Sumio Iijima in 1991, soon after the Smalley discovery was first announced.

Stronger than steel, more conductive than gold, and with electrical characteristics of either metals or semiconductors, carbon nanotubes have been at the center of a great deal of nanotechnology research at IBM's T. J. Watson Research Center, and other laboratories worldwide. The electronics industry is pushing the dimensions of transistors in commercial chips down into the nano dimensions. In other applications, carbon nanotubes are being used as reinforcing materials in composites today, making stronger parts for lighter vehicles possible. DNA molecules, about 2.5 nanometers wide, are also being used in the development of new materials both in electronics and in medicine using nanotechnology.

Nanotechnology and Moore's Law

Part of the momentum for the rise in nanotechnology comes from the realization by the semiconductor industry as it has had to come to grips with Moore's law, a driving force of the digital era. Moore's law is not a law of nature or government but an observation made in 1965 by Intel co-founder Gordon Moore when he plotted the growth in memory chip performance versus time. That observation described the trend that has continued to be remarkably accurate. He observed that the number of transistors that can be fabricated on a silicon integrated circuit is doubling every 18 to 24 months. Moore's observation held true for over 4 decades. But the Law is in trouble. It is expected that the industry will be making components down to the 100 nanometer range by 2005. At that point the quantum mechanical world of atoms and molecules takes over and the physics of the larger world no longer applies.

In response to the fundamental problems with Moore's law, Stan Williams, director of the quantum structures research initiative at Hewlett-Packard Labs, says over the next 10 years researchers believe a hybrid molecular/silicon technology will evolve that utilizes the best of both worlds. Some see quantum computers as the future. Williams believes they are out there, possibly more than 10 years away. He also predicts by 2020 electronics will be 10,000 times as capable as they are today due to nanotechnology research.

Although the challenges of Moore's Law will dominate nanotechnology research in the next decade, as it has driven it in the past decade, there are other important areas of research benefiting from it. With an increased demand for drugs to solve all ills, there are a number of remarkable nanodevices that could make a difference in the not-too-distant future. A team under the direction of Jean M. Frechet at the University of California, Berkeley, is working on drug delivery with dendrimers, chemical nanodevices. iMEDD, a startup drug delivery company, has a patented process using nanomembranes to produce a controllable rate of drug release.

One product of nanotechnology that has made the news for its novelty has been described as "smart bombs" for the connection to its funding source. The development of the novel technology from the Baker Laboratory at the University of Michigan Medical School was funded by the U.S. government Defense Advanced Research Project agency (DARPA). The nanobombs are molecular-size droplets that proved to be 100% effective in a test as a potential defense against anthrax attacks. The application, it is hoped, will never be needed. But, the formulation can be adjusted to attack such disease organisms as those causing influenza and herpes.

DNA nanoparticle-based probes and detection and screening assays are being developed at Nanosphere, Inc., a startup company incorporated in 2000, and founded by Chad Mirkin of Northwestern University and a colleague, both pioneers in the field of DNA and nanoparticle research. Chad Mirkin is the Director of the Institute for Nanotechnology and Center for Nanofabrication and Molecular Self-Assembly at Northwestern. (It might be an exaggeration to say that every university is doing research in nanotechnology, but it's not a large exaggeration.)

Mirkin and his colleague found that single-stranded DNA can link metal nanoparticles in a way that controls the structure's optical properties. The method relies on a specific color change that occurs when the functionalized nanoparticles, which look red in solution, are induced to form nanoparticle aggregates, which are blue in solution. A conspicuous color change makes them useful in diagnostic testing for many forms of cancer. The test procedure can be modified to be used for virtually any sequenced organism or genetic disease. The procedure can also be used for food testing.

With the proliferation of nanotechnology research, the driving forces of a worldwide economy that is tied to the advance of electronics, and a society that demands medical progress, the question of whether the potential dangers of nanotechnology to society outweigh the potential benefits may be an entirely academic debate. The genie is out. Society has tasted the successes of nanotechnology and they are many. Even with the science fictionese suggestion of replicating robots, gray goo and all, nanotechnology is here to stay.

—M. C. NAGEL

Further Reading

Barinaga, Marcia. "Asilomar Revisited: Lessons for Today?" <http://www.usc.edu/dept/law/Pacific_Center/Main_Links/Asilomar/Science_article.html> .

Barlow, John Perry. "Is Technology a Threat toHumanity's Future?" <http://seattletimes.nwsource.com/news/business/html98/techweb_20000319.html> .

Crandall, B. C. Nanotechnology: Molecular Speculations on Global Abundance. Cambridge, Mass.: MIT Press, 1996.

Drexler, K. Eric. Engines of Creation. NewYork: Anchor, 1987.

——. Nanosystems: Molecular Machinery, Manufacturing, and Computation. New York: John Wiley & Sons, 1992.

Gross, Michael. Travels to the Nanoworld: Miniature Machinery in Nature and Technology. New York: Perseus Books Group, 1999.

Joy, Bill. "Why the Future Doesn't Need Us." Wired 8.04 (April, 2000) <http://www.wired.com/wired/archive/8.04/joy.html> .

Kahn, Herman. On Thermonuclear War. Westport, Conn.: Greenwood Publishing Group, 1978.

Krieger, Lisa M. "Genetic Researchers CiteSpecter of Profits Asilomar: Scientists Say Demands for Financial Gain Threaten Public Health by Concealing Dangers." <http://www.biotech-info.net/asilomar_mercury_news.html> .

"Nanoelectromechanical Systems Face theFuture." <http://www.physicsweb.org/article/world/14/2/8> .

"Nanotechnology: The Coming Revolution inMolecular Manufacturing." <http://www.foresight.org> .

"Preparing for Nanotechnology." <http://www.foresight.org/index.html> .

"U.S. Nanotechnology Initiative." <http://www.nano.gov> .

KEY TERMS

BIOVOROUS:

Means literally life eating. The term was used to describe the possible destructive forces of replicating nanorobots.

GLOBAL ECOPHAGY:

From eco—the environment, and phagy—to eat or consume something. The term refers to the possibility of replicating nanorobots running amuck and consuming their, and our, environment.

NANOTECHNOLOGY:

The science of manipulating atoms and molecules. Nano comes from the Greek for dwarf. It is a prefix meaning one billionth. A nanometer is about the width of 3-5 "average" atoms, or 10 hydrogen atoms, hydrogen being the smallest of all atoms.

QUANTUM:

Literally means how much? The term evolved to describe the motion and interaction (quantum mechanics) of particles in the range of nanometer size where the forces of their interaction make classical laws of motion as described by Newton not relevant.

NANO DIP-PEN

The nano dip-pen could be the key to making computer nanocircuits, and possibly needle-tip sized medical instruments. It can now be used to modify existing circuits especially for sensors. Chemistry Professor Chad Mirkin and his colleagues at Northwestern University's Center for Nanofabrication and Molecular Self Assembly call their discovery dip-pen nanolithography.

The new writing tool is able to use an organic oily ink to make nano-scale letters with near-perfect alignment. The area surrounding them can be filled with a second type of ink. Some of the technology that makes the device work is remarkably similar in principle to dippens that Mirkin estimates have been used for 4,000 years (although not too much in recent times). The pen is another story.

Mirkin's new dip-pen nanolithography uses an atomic force microscope (AFM) with an extremely fine pen tip made of silicon nitride. The "paper" is gold-plated silicon and the "ink" is a single layer of molecules called ODT that were selected because they are attracted to the writing surface. The ink is first allowed to dry on the tip, then the tip is brought in near contact with the surface. A water meniscus forms between the surface and the coated tip. The size of the meniscus is controlled by relative humidity. The appearance of water on the surface had been considered an obstacle to the AFM operation by earlier researchers, but Mirkin's team found that it was the key to success for nano dip-pen lithography. The team turned a major problem into a solution.

To demonstrate the success of nano dip-pen lithography, the Northwestern University researchers printed a nano-sized excerpt from physicist Richard Feynman's written version of his famous December 1959 speech, "There's Plenty of Room at the Bottom." Feynman's speech is considered the beginning of nanotechnology.

—M. C. Nagel



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