Molecular nanotechnology or "nanotech" as it is popularly called is the technology of manipulating materials at the molecular level or the "nanoscale (a nanometer spans only three or four atoms.)" And while that may appear futuristic, it is not: Design rules of silicon chips have already dropped below 100 nanometers.
Nobel laureate Richard Feynman first publicized the idea of nanotechnology in a talk that he gave on December 29th, 1959, at the annual meeting of the American Physical Society at the California Institute of Technology (Caltech) entitled, "There's Plenty of Room at the Bottom." There he described an "ultimate vision," the possibility of vertically integrating manufacturing right down to the individual atom. By starting at the "bottom," in Feynman's words, atomically precise manufacturing methods could be the ultimate in miniaturization. "There is nothing that I can see in the physical laws that says the computer elements cannot be made enormously smaller than they are now. . .the wires should be 10 or 100 atoms in diameter, and the circuits should be a few thousand should be 10 or 100 atoms in diameter, and the circuits should be a few thousand angstroms [100 nm] across," said Feynman, in his 1959 talk. He went on to encourage designers to think small, because, in his opinion, all it would take to get there would be ingenuity. "The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom. It is not an attempt to violate any laws; it is something, in principle, that can be done; but in practice, it has not been done because we are too big," said Feynman.
Feynman's overall concept was that when engineers begin to precisely manipulate matter at the atomic level, we would finally achieve what the alchemists sought in the Middle Ages we would be able to take whatever raw atoms are available and rearrange their neutrons, protons and electrons into whatever we want with nothing left over. During his 1959 talk, Feynman went on to offer a $1,000 prize for the first electric motor small enough to be contained inside a 1/64 inch cube. Today, the Foresight Institute has picked up the baton with an annual "Feynman Prize in Nanotechnology ($5,000) and the Feynman Grand Prize ($250,000).
Feynman's dream sparked the imagination of a generation of dreamers including a faction whose thinking extended into science fiction. Their dreams exceeded those of the ancient alchemists in proposing that individual atoms of inexpensive raw materials garden variety dirt could be rearranged into complex, fully formed electromechanical devices or just about anything that is "manufactured." Science fiction authors began speculating on how virtually any kind of mechanical, chemical or complex electromagnetic device could be constructed with "nano-robots" automatic "assemblers" working atom-by-atom.
At least some of this dreaming became feasible in 1982 when manipulation of individual atoms become possible thanks to the invention of a breakthrough tool called the scanning tunneling microscope (STM), which won its inventors, IBM researchers Gerd Binnig and Heinrich Rohrer, the 1986 Nobel Prize. The same year the duo followed up by co-inventing yet another tool, the atomic force microscope (AFM). More than anything else, scanning probe microscopy (including both atomic force microscopy and scanning tunneling microscopy) gave birth to nanotechnology. A probe only a single-atom wide, enabled engineers to "push" atoms into "designer" molecules. IBM's Zurich Research Laboratory has subsequently demonstrated that the tips could be used to store bits by impressing 10 nm marks in a soft polymer sheet, thereby packing a terabit per square inch the so-called Millipede memory chip (see "IBM stores terabits of memory on a single chip," EE Times, June 24, 2002, http://www.eetimes.com/story/OEG20020624S0030).
Soon after scanning probe microscopy made possible that manipulation of atoms, Eric Drexler, now chairman of the Foresight Institute, released his 1986 book Engines of Creation, which popularized the term "nanotechnology" and fleshed out its "ultimate vision." Drexler predicted that nanoscale assemblers would automatically assemble molecular building blocks into nearly any type of manufactured good watch to watchtower.
The term "nanotechnology" itself was coined in 1974 by Tokyo Science University professor Norio Taniguchi, author of "Nanotechnology: Integrated Processing Systems for Ultra-Precision and Ultra-Fine Products" (Oxford Science Publications), but he used the term to signify machining traditional silicon to tolerances of less than a micron. Taniguchi's original concept submicron machining of silicon has already produced a number of tiny mechanical devices that today are called microelectromechanical systems (MEMS). MEMS are the most highly developed application of nanotechnology today from air-bag sensors in automobiles to thin-film heads for disk drives.
Meanwhile, the world's first company dedicated to Drexler's ultimate vision Zyvex Corp. (Richardson, Texas, www.zyvex.com) hopes to create nano-assemblers by downsizing MEMS to the nanoscale through the nanoelectro-mechanical systems (NEMS) project for the Advanced Technology Program at the National Institute of Standards and Technology (NIST), along with Standard MEMS Inc. and university collaborators Rensselaer Polytechnic Institute Center for Automation Technologies, the University of Texas at Dallas, and the University of North Texas. Similar research is proceeding separately at big corporations like IBM, Hewlett-Packard, Motorola and Raytheon.
The federal government has enlisted the help of universities and smaller companies with its National Nanotechnology Initiative funded with over $500 million, and with separate programs inside its own research facilities at national labs and the National Aeronautics and Space Administration (NASA, www.nasa.gov). The New York City-based NanoBusiness Alliance (A HREF = "http://www.nanobusiness.org">http://www.nanobusiness.org) claims that over $1 billion will be spent in nanotechnology research and development in 2003. Venture capitalists have been investing for several years. Draper Fisher Jurvetson, for instance, has already invested $40 million to start up 12 new nanotechnology ventures, like NanoOpto Corp. (specializing in subwavelength optical NEMS and nano-imprint lithography, http://www.nanoopto.com). The Texas Nanotechnology Initiative (http://www.texasnano.org) also tracks venture investments, estimating that $1 billion will be invested in researching electronic applications of nanotechnology over the next five years.
Nanotechnology research today uses three types of well-understood molecular building blocks proteins, polymers and carbon nanotubes. (Carbon nanotubes are rolled hexagonal graphite sheets grown from carbon 60, also known as Buckminsterfullerene, a geodesic-dome-shaped molecule, which, together with other fullerenes such as C70, now constitutes the third elemental form of carbon, after graphite and diamond).
Proteins, which are building blocks of DNA, have recently been harnessed with atomic precision by biochemists with the help of gene copying machines used by genome researchers. These mainly one-dimensional structures can be accurately grown in repetitive patterns according to rules designed into to their "seeds" similar to crystal growth patterns. Researchers like professor Carlos Bustamante at Howard Hughes Medical Institute, professor Andreas Engel at the University of Basel (Switzerland) and professor Steve Block at Stanford University have all made progress at rearranging proteins into atomically precise "designer" molecules that could serve as a nanoassembler's building blocks, in the long term, or in the near term as components in hybrid systems. Even IBM got into the protein act in 2000 (see EE Times, Sept. 13, 2000, http://www.eetimes.com/story/OEG20000913S0061) when it used the "lock and key" molecular recognition mechanism built into protein molecules, in an early biological application of nanotechnology. A MEMS "comb" had each tooth pretreated with a specific molecular "key," making it deflect in the presence of a single type of molecule. By measuring the deflection, IBM was able to detect DNA strands with only a single missing bond on a long protein chain, a feat impossible in real-time using conventional equipment.
The second category of possible building blocks for delivering on nanotechnology's ultimate vision is polymers. Several different researcher groups have demonstrated that Brownian motion the random "mixing" of molecules in a liquid or gas can exhibit auto-assembly if the parts are pretreated a la IBM's lock-and-key application. For instance, Sandia National Labs, a pioneer in MEMS technology, has demonstrated that small molecules with the edges pretreated so that they can only bond together with the correct other parts, auto-assemble into atomically precise molecular building blocks (see "Experiments refine self-organizing principles" EE Times, Oct. 23, 2001, http://www.eetimes.com/story/OEG20010917S0076).
Carbon nanotubes are the most promising of all building blocks for nanotechnology for the short term certainly the next five years. Besides being stronger than steel, carbon nanotubes exhibit many fascinating electronic properties, such as: ballistic transport of electrons at room temperature, the ability to serve as the channel of a silicon transistor, and the ability to behave like either a p-type and n-type semiconductor without having to doped (see "Nanotechnology creates 1-terabit memory," EE Times, http://www.eetimes.com/story/OEG20020611S0018).
IBM recently demonstrated a transistor using a single carbon nanotube a prototype that could be packing terabits of information on memory chips within five years. Right now, however, the most successful electronic application of nanotechnology has been the carbon nanotubes themselves. Measuring only 1 to 2 nanometers in diameter, they are being fitted to scanning probe microscopes for even easier manipulation of individual atoms. They are also being prepared as additives for just about everything from rubber-as-strong-as-steel to emitters for microscopic vacuum tubes (see "Vacuum tubes born again in nanotube MEMS", EE Times, June 17, 2002, page 51).
Companies like Carbon Nanotechnologies Inc. and Applied Nanotechnologies Inc. are growing nanotubes to the specifications of a diverse set of future applications. Carbon Nanotechnologies, for instance, co-founded by Carbon 60 discoverer Richard Smalley, is developing carbon nanotubes called "buckytubes" single-walled carbon nanotubes produced by a proprietary process. Smalley, Harold Kroto and Robert Curl won the 1996 Nobel Prize for their discovery of carbon 60 fullerenes (buckyballs). Applied Nanotechnologies, on the other hand, develops applications for carbon nanotubes to improve existing devices, such as field-emitter cathodes for microwave amplifiers, gas discharge tubes as well as pocket-sized X-ray- and e-beam-machines.
Many nanotube-based devices have been demonstrated in the laboratory that, while falling short of self-replication or auto-assembly, nevertheless may become very important to chip makers. University researchers have paved the way, starting with Richard Smalley's own research group at Rice University. Many other groups have made important contributions too, such as Cees Dekker's Molecular Biophysics Group at Delft University of Technology (Lorentzweg, The Netherlands) and professor Paul McEuen's group at Cornell University, both of which paved the way early-on by characterizing carbon nanotubes. Likewise, professor Sumio Iijima at the Japan Science & Technology Corp. (Kawaguchi City, Japan) has been coordinating that country's characterization of nanotubes and related electronic applications of nanotechnology. Stateside, Harvard University professor Charles Lieber's research group has demonstrated how to grow silicon nanowire building blocks as electronic components that can be assembled into molecular-sized circuits. Big corporate internal research groups are also getting into the act, including IBM, HP and Bells Labs, Lucent Technologies
Over the next five years, carbon nanotubes will likely be integrated into hundreds of applications. Carbon Nanotechnologies has already licensed its carbon-nanotube manufacturing process to DuPont for its flat-panel display group, which will use them as thick-film emitters resulting in a display that is lighter, thinner and more energy-efficient than today's. Dow Chemical is likewise gearing up to offer what they call "affordable and well-performing nanomaterials" to its existing customer base, such as Ford Motor Co. Traditional semiconductor makers are also getting in the act, from Motorola Inc. to NEC and Samsung. For instance, Motorola's Physical Science and Research Laboratories are characterizing nanotubes, to each end of which they have successfully added single-molecule electrodes, in the hopes of shrinking and accelerating the performance of future sensors. Soon the mother of all nanotube applications flash memory replacement will likely bear fruit at IBM, packing billions of transistors into the space now housing only millions and, once again, extending Moore's Law.
Why now? Intel co-founder Gordon Moore's so-called "law" is actually a prediction that every 18 months semiconductor fabricators will be able to cram twice the number of transistors on a microchip. However, lithographically patterned semiconductor technology is running up against physical and economic constraints in its quest for smaller dimensions the state of the art is only a few hundred nanometers and faster performance. Not the least of the concerns is the soaring costs of all this downsizing.
Nanopatterning the extension of photolithographic techniques into the nanoscale domain will assist in reducing chip sizes further, extending the lifetime of traditional transistors. But more importantly, nanopatterning will assist in the placement of nanotubes into otherwise conventional silicon transistors. Many groups are demonstrating methods to nanopattern traditional silicon to below 100 nanometers. For instance, Stephen Chou's team at Princeton University has demonstrated a laser-assisted direct imprint technique that may be able to shrink feature sizes to 10 nm (Chou fires his laser through a printing mask made from quartz to directly melt the surface of the silicon for "etch-less" nanopatterning of silicon chips.)
Even with nanopatterning, there remain many hurdles such as heat dissipation and interference between the tiny components. HP's Quantum Science Research Lab claims that it will take a decade of intensive research to wear down the nitty gritty engineering problems that crop up at these small scales. HP fellow and director of the company's Quantum Science Research Laboratories, R. Stanley Williams, recently revealed a nanotechnology patent, shared with HP's Phillip Kuekes and UCLA scientist James Heath, that enables a crossbar grid of nanoscale wires, separated by a single molecule thickness of rotaxane, to form switches between selected intersections by electrically activating the rotaxane molecule between them.
Even with the extension of chip-making techniques into the nanometer domain, nanotechnology proponents claim further size reductions may need a new approach from the bottom up (atom-by-atom) rather than from the top down as in conventional lithograhphy.
The "top-down" approach currently practiced in chip-making forces us to spend more and more on higher and higher precision machinery to make smaller and smaller photolithographic lines for the ever shrinking size of chip features. It's a trend in common with all manufacturing processes today that attempt to make smaller devices today's manufacturing processes are subtractive processes that start with large assemblies of molecules. It is likely that nanotech approaches that start by aggregating individual atoms or molecules could address all such manufacturing needs.
Indeed, in a nanotechnologist's ideal world every engineer's design would be married to a perfectly vertical manufacturing technology that harvests its own raw atoms, makes them into perfect molecules for a specific applications, assembles these perfect molecular building blocks into smart materials, assembles the materials into subsystems, and assembles the subsystems into finished devices.
But the problem with that kind of thinking is that without the availability of extremely small and extremely fast assemblers, such vertical integration simply isn't possible. Manipulating materials atom by atom manually would take eons even to build even the simplest systems.
But proponents of this vision take heart from the fact that Nature routinely exhibits encoding mechanisms that could, theoretically, be used to "program" smart materials into automatically assembling themselves. Nature auto-assembles all its molecules into subsystems and the subsystems into finished devices, whether it is "growing" crystals from atoms or growing full-blown biological systems from a single fertilized egg cell.
Nanotech's ultimate vision conjures up armies of man-made nano-assemblers spinning out plastic as strong as steel, much the way wood is spun out by the "assemblers" in a tree. To scale up to the task size, these self-replicating molecular assemblers would make copies of themselves from molecular building blocks until they had enough of themselves to perform the task at hand, be it assembling a microchip or a highway. Much science fiction is made of the amazing scales of economy that could be reaped by this approach, and an active search is on in scientific circles for molecular designs that can serve as the "tools" and "dies" for such nanoscale construction projects.
Critics are not so optimistic. Besides the usual doomsday predictions of self-assembling nano-robots running amok, at least one well-placed critic challenges the feasibility of realizing the ultimate vision. Nobel laureate Richard Smalley is no doomsayer, since he co-founded one of the most promising nanotech companies (Carbon Nanotechnologies). Nevertheless, Smalley's poignant criticism is that molecular auto-assembly, as proposed by Feynman and Drexler, is just too ambitious. In particular, Smalley says that the "fat-" and "sticky-finger" problems will prevent the success of the necessary auto-assembly steps. Others claim that such fine-scale materials will be too brittle, lacking the strength for macroscopic projects. Still others charge that the second law of thermodynamics will foil the ultimate vision (nanoscale friction generates too much heat, essentially making it impossible to scale up from nano-sized to macroscopic devices).
The 'beginning' of life
On the positive side, most of the advantages of nanotechnology will be reaped along the way to the ultimate vision. Why? Because nanotechnology is at the "beginning" of its lifetime, whereas silicon technologies are at the end of their lifetimes. Nanotechnology can only ascend reaping geometrically increasing benefits as each succeeding layer of knowledge builds on the one before.
In contrast, top-down manufacturing methods, such as semiconductor manufacturing processes, are increasingly expensive as they attempt to scale down. Nanotechnology benefits will be able to bootstrap the advantages of bottom-up discoveries as they are uncovered. First, engineers will learn how to add auto-assembling techniques to existing silicon chips, which will help in learning how to coax these smart materials into auto-assembling subsystems, and eventually auto-assembling subsystems into devices at least in theory.
In nanotech-land, chemistry meets silicon micromachining techniques through a melding of the appropriate natural laws. The mechanisms that bond atoms together into useful molecules are well-understood, as are the principles governing the growth of crystals. Together these chemistries can control how raw materials are transformed how sand is processed into microchips. Unfortunately, today all the reagents and catalysts and other chemicals needed to promote the desired reactions inevitably lead to byproducts, many of which are unwanted.
Nanotechnology ups the ante by downsizing chemistry from mixing vats containing billions of atoms, to individual atoms bonding together into smart molecular building blocks. Using molecular modeling software, engineers of the future will design molecular building blocks that fit perfectly with each other. Byproducts would be completely eliminated ultimately. Early applications, however, will be successful because they have just one nanoscale aspect transistors using nanotubes as the channel, for example.
Auto-assembly would be a useful property no matter the scale, but is not used today for economical reasons-it is usually more economical to build a machine that makes a part, rather than design a "smart" part that can make itself.
But even if nanotechnology's ultimate vision of large-scale molecular self-assembly is never realized, the field itself will yield a variety of benefits through an understanding of how materials can be manipulated at the nanoscale.
Along the long-range development cycle to the ultimate vision of molecular self-replication and auto-assembly, there will be many milestones. In fact, there are so many advantages to acquiring precise control of materials at the atomic-level that the original goal of self-replication and auto-assembly could be easily obscured. Materials specialists have long used nanoscale additives to make certain goods more durable: Carbon black, which consists of nano-sized particles, has been strengthening the sidewalls of automobile tires for 100 years. Such nanomaterials from 3M, Monsanto and others will reap nano-related benefits long before we have any sort of nano-assemblers.
In recognition of these benefits one investment house in Tel Aviv the Millennium Materials Technologies Fund has decided to focus on funding only nanotech materials makers. Many U.S. businesses are following suit. For instance, Applied Science Inc. (Cedarville, Ohio) has patented a multiwalled carbon nanotube material, called Pyrograf, and is marketing it as an additive that makes polymers stronger and conductive. Its customers include General Motors Corp. and Goodyear who are constantly on the look out for weight- and cost-reduction techniques in automobiles., The semiconductor industry is evaluating the material for everything from semiconductor handling trays to a thermal backing for next-generation microchips.
A number of composite materials use nanotechnological approaches. Magnetoresistive heads for hard disk drives use layers of composite material measuring just a few nanometers thick. Molecular control maintains the purity of these layers. which are combined to form macroscopic systems the recording head itself.
Other nanotech materials exploit various aspects of submicron-sized particles, such as the use of "quantum dots" as biological markers. Companies like Quantum Dot Corp. are capitalizing on work dating back to the 1980s performed separately by researcher Louis Brus at Bell Laboratories and researcher/collaborators Alexander Efros and A.I. Ekimov of the Yoffe Institute in St. Petersburg (Russia) which harnesses silicon nanoparticles. Quantum Dot and others are extending that work by fabricating silicon nanospheres that are smaller than the Bohr's radius of silicon (the natural distance between electron-hole pairs in silicon). Stimulating these nanoparticles with low-energy radiation while their electron-hole pairs are confined enables them to store more energy than their usual quantum states would allow, resulting in emissions that are shifted to visible wavelengths. Quantum Dot's patented "Qdot nanocrystals" can be attached to specific human drugs/antibodies, to be used as fluorescent biological markers. In computer applications quantum dots can be made to switch like transistors, only better, since quantum states hold both a "0" and a "1" simultaneously, permitting parallel calculations.
Materials specialists are even applying nanoparticle technology to mundane applications, such as suntan lotion. Nano-sized zinc oxide particles produced by Nanophase Technologies one of the few publicly traded nanotech companies create a transparent zinc-oxide sunscreen because their tiny size makes them invisible.
The company is currently applying its nanotechnologies to ceramics based on nanocrystalline aluminum oxide and ZTA (zirconia-toughened alumina), as well as other transparent coatings that are abrasion-resistant, dissipate static and, when formed into films fabricated from antimony and indium, can conduct electricity.