A publication of the Foresight Institute
Molecular nanotechnology has moved to the top of the agenda at the National Science Foundation. In recent months, NSF has:
In testimony before Congress on April 1, seeking support for his $3.8 billion fiscal year 1999 budget request, NSF Director Dr. Neal Lane said:
"If I were asked for an area of science and engineering that will most likely produce the breakthroughs of tomorrow, I would point to nanoscale science and engineering, often called simply 'nanotechnology...'
NSF support over the years has allowed nanoscale science and engineering to go from the realm of science fiction to science fact. One of the most notable NSF-supported discoveries was the Nobel Prize winning discovery... of a hollow form of carbon known as Buckyballs. Subsequent research has shown that a related class of molecules--the fullerenes--can form 'nanotubes' only a few atoms in diameter that could be the basis for a stunning array of new environmentally friendly, carbon based materials never known before.
The possibilities of nanotechnology are endless. Entirely new classes of incredibly strong, extremely light and environmentally benign materials could be created. Other possibilities include:
Some nanoscale scientists and engineers even envision nanomanufactured objects that could change their properties automatically or repair themselves. When you think about it, this idea is not so outlandish--DNA molecules in our own bodies can replicate themselves with incredibly small rates of error. Much of the inspiration for nanoscale scientists and engineers comes from the biosciences and bioengineering--making nanoscale science a perfect example of the integration of the physical sciences and biosciences."
- New generations of metals and ceramics several times harder and more ductile that today. This could enable the creation of inexpensive and readily available superconductive materials;
- medical implants that are constructed to be accepted by the body; and
- medical probes so small that they won't damage the tissue.
NSF also has announced its intention to sponsor a Forum to be held in conjunction with the Sixth Foresight Conference on Molecular Technology. It will be moderated by Prof. M.C. Roco, NSF, Chair of Interagency Nanotechnology Group. The Forum will address the following issues:
Invited lectures from industry, universities and national laboratories will analyze the path from exploratory research and new fundamental discoveries at nanoscale to emerging technologies. Time for questions, discussion and group interaction will be provided. Invited speakers and their topics are:
Viewed in the context of these more recent developments, NSF's earlier announcement of a $10 million funding initiative in nanotechnology for FY 1998 takes on even more significance. Entitled "Partnership in Nanotechnology: Synthesis, Processing, and Utilization of Functional Nanostructures (FNS)," the grant called for proposals to be submitted with deadlines in February. Grant recipients have not yet been identified, but the thrust of the initiative is clear. The project description defines nanotechnology for purposes of the initiative as, "...technology that arises from the exploitation of physical, chemical and biological properties of systems that are intermediate in size between isolated atoms/molecules and bulk materials, where phenomena length scales become comparable to the size of the structure. The discovery of novel phenomena and processes at the 'nano' scale (1-50 nm) and the development of new experimental and theoretical tools in the last few years for investigating these structures provides fresh opportunities for scientific and technology developments in nanoparticles, nanostructured materials and nanodevices." Although this definition does not explicitly limit the initiative to "bottom up" molecular nanotechnology, it clearly embraces that concept.
Recognizing the interdisciplinary nature of nanotechnology, the NSF initiative "encourages team approaches to functional nanostructures research in the belief that a synergistic blend of expertise is needed to make major headway. Theoretical modeling, synthesis, processing with a focus on building up from molecules and nanoprecursors, utilization, and characterization of structure and properties are components of this activity. Hence, this initiative has the aim of fostering interactions among physical, mathematical, chemical, biological and engineering disciplines by encouraging small groups of experts (up to 4 principal investigators) in these different fields.
"The initiative will support research on new concepts and methods for the generation of functional nanostructures, including synthesis and processing of nanoparticles and other precursor structures, self-assembly techniques, supramolecular chemistry, electronically and chemically functional structures, creation of bio-templates and sensors, 'smart' materials and films, and fabrication of nanostructured materials, nanocomponents and nanodevices with unusual properties. The initiative does not include routine measurements research, conventional lithography, or purchase of large experimental facilities."
The initiative focused on four "high-risk/high-gain research areas, where special windows of opportunity exist for fundamental studies in synthesis, processing, and utilization of functional nanostructures":
Details on the NSF initiative and additional information about NSF's growing interest in nanotechnology are available at http://www.nsf.gov/home/crssprgm/nano/
|Foresight Update 33 - Table of Contents|
The 1998 Spring national meeting of the American Chemical Society in Dallas, in late March and early April, included a day-long symposium on topics related to molecular nanotechnology. The symposium, entitled "Device Applications of Nanoscale Materials" (Chemical & Engineering News, April 20, 1998) was funded by the ACS Corporation Associates Pilot Grants for Industrial Programming, American Chemical Society Division of Physical Chemistry.
The symposium sought to demonstrate current and innovative applications of chemistry in the nanometer size regime for use in optoelectronics and to identify potential areas for partnerships between industry and academia where research in nanoscale chemistry can be applied to emerging technologies. It was hoped that this symposium would benefit chemists working in nanotechnology by providing a forum for discussing applications with leading industries.
Some of the speakers concentrated on research involving "top down" technologies of more immediate interest to the semiconductor industry. This report will concentrate on presentations of research directed toward achieving molecularly precise structures.
Jie Han of NASA Ames Research Center discussed the potential for using carbon nanotubes as electronic devices. The electronic properties of single walled carbon nanotubes can change as changes the configurations between hexagons along the nanotube walls and as the diameters of the tubes are increased. Theoretical studies and physical measurements using lithography combined with scanning tunneling microscopy (STM) by various research groups have shown that different tubes can act as either semiconductors or metallic wires. Since a single walled tube can be as small as 1.0 nm in diameter, nanotubes have potential as components for nanoscale electronics. Dr. Han uses molecular modeling studies to simulate the production of electrical devices based on carbon nanotubes with varying electronic properties connected in circuits.
Carbon nanotubes also have unique mechanical properties. Work by Charles M. Lieber et al. at Harvard (Science 277, 1997) using atomic force microscopy (AFM) shows that nanotubes are considerably strong, and elastic, possessing a Young's Modulus similar to that of bulk graphite (the largest of any known material). Dr. Han showed simulations of unique gears and motors based on carbon nanotubes, however these have not yet been produced by scientists.
James M. Tour of the University of South Carolina described his work to create "a world of nonmetallic wires based on molecules with conjugated carbon-carbon bonds." His group has synthesized potential molecular wires equipped with molecular alligator clips (thiol groups) for attachment. Tour's group has shown that the molecules behave as wires by probing them individually through scanning tunneling microscopy. Recently, they have measured the amount of current that can be carried by a single molecule. Tour's group is now designing molecules with more sophisticated architecture so that they behave like transistors or switches. For example, he presented a design of a three-armed molecule that is expected to behave as a NOT logic gate.
However, the potential heat output of a molecular-sized computer chip "starts to approach power densities similar to that in a nuclear reactor as far as temperature is concerned," Tour said. For that reason, he and a colleague, Jorge M. Seminario, are exploring a scenario where the transfer of one bit of information "requires about one-millionth of an electron" by developing molecular systems in which "one molecule perturbs the electrostatic field of another" rather than actually transferring electrons. Tour has predicted that such concepts may be realized within the next five years, and that he expects demonstration of molecular-sized devices that act like a transistor within two or three years. "Either by us or by some other group," he told Chemical & Engineering News. "The race is on." How long before molecular devices are functioning in commercial computers? "My guess is 10 to 15 years," Tour told the magazine.
Both Han and Tour presented their work at the Foresight Institute Fifth Conference on Molecular Nanotechnology last November in Palo Alto.
James Von Ehr, founder of Zyvex LLC, discussed the studies his company is making on molecular manufacturing. Most of his work is currently proprietary. He discussed the direction his company is taking toward positioning and modeling molecular manufacturing systems using the principle of mechanochemistry, in which atomic and molecular building blocks are transported and presented to their reactive sites with precise positional control. To achieve this result, reaction dynamics must be carefully modeled and positional devices must achieve accuracies of better than one-half bond length. Von Ehr showed models of movement systems for transporting molecular building systems. The speech presented many ideas and goals which must be achieved for such molecular mechanical systems to be realized.
Jeffery L. Coffer presented research on the gas phase formation or silicon nanoclusters doped with rare earth ions. Working with graduate student John St. John from Texas Christian University and materials science researchers Russell F. Pinnizzotto and Yan Dong Chen of University of North Texas, Coffer has shown that rare earth doped silicon nanoclusters can be produced by high temperature decomposition of disilane gas in conjunction with a rare earth ion. Decomposition of disilane in this manner forms silicon nanoclusters 2-12 nm in diameter depending on the length of the high temperature oven (1000° C). Placing a rare earth chemical vapor deposition precursor (CVD) into the gas stream with the disilane forms nanoclusters with rare earth ions trapped inside. The rare earth ions emit light at specific discrete wavelengths due to the nature of 4f electrons which are protected from bonding and electronic effects. A critically important rare earth ion, erbium has been well studied in bulk silicon because it emits light at 1.54 microns (near IR). This wavelength is important technologically because it falls at a point of minimum loss for silica based optical fibers. This research represents the first overall synthesis of discrete silicon nanoclusters doped with erbium from the gas phase.
John St. John is a graduate student studying inorganic materials chemistry at Texas Christian University in Fort Worth, Texas. He can be reached via e-mail at: firstname.lastname@example.org.
From Foresight Update 33, originally published 30 May 1998.