Over the past few years, Midnight Engineering has attempted to bring to its
readers assessments and reviews of various technologies, development tools, and
specific technical products as a window through which developers and engineers
could view possibly useful information which could affect their own
entrepreneurial efforts. There are, however, those occasions when a radical, new
technology begins to emerge, which has fundamental implications over a very wide
range of areas of interests, and applications. It is in this light that an
overview of nanotechnology is discussed here, and no doubt will be at the heart
of many newly emerging technologies of the near future.
In fact, it would be difficult to envision a more encompassing realm of future development, which may in fact evolve to a situation no less important than what the industrial revolution was nearly two centuries ago, or what the information revolution has become today. What could possibly justify such a seemingly grandiose observation? Applications ranging from molecular computing, specialized materials with very unusual properties (such as shape changing alloys, synthetic "organic" compounds, super- conductive semi-conductors, etc.), custom gene construction on demand, to ultra miniaturized machinery which can have all of the complexity of traditional mechanical components, but on a cellular and subcellular scale, are just a few of the areas of re- search already well under way.
Indeed, the entire methodology that engineering teams may decide to approach various design or development problems may be fundamentally changed. The basic concept of nano construction techniques (although not specifically limited to this specific definition) is to construct objects and components by assembling molecules together to form molecular subassemblies, and interconnecting these molecular components to form larger, more complex assemblies, and so on. This is radically different than the "traditional" construction approach, which is to start with a massive "block" of some material, and attempt to machine it to some smaller, intricate piece of material that will become part of some assembly.
At the risk of being immediately contradictory, there are, of course, also those researchers who are in fact using "traditional" construction techniques, such as photolithography, laser machining, and other approaches at extremely small scale manipulation, to carve and construct nano-mechanical components out of blocks of material. In fact, in many future applications, particularly in the realm of micro-robotic and mechanical components, it will most likely be a combination of molecular construction and micro-machining utilized to achieve the desired results.
However, in the "purist" realm of true nano technology as an applied science, there is a body of researchers throughout the world who are at the cutting edge of exploring how to manipulate individual molecules, and even atoms, to accomplish specific design or activity tasks. It is important to note here that nanotechnology is not a single "thing", or scientific discipline, but rather a concept that encompasses a very wide range of areas of research and development, including (but certainly not limited to) computer science, physics, chemistry, medicine and physiology, and quite possibly an entire array of scientific specializations never before considered practical, or even possible.
Perhaps no one individual better exemplifies this body of research than Dr.
K. Eric Drexler, (former MIT and Stanford professor, and current head of the
Foresight Institute in Palo Alto, CA) 
who is respected worldwide as arguably the leading authority in this newly
emerging science. In fact, his most recent book on the subject, Nanosystems -
Molecular Machinery, Manufacturing, and Computation, is considered to be "the"
technical reference manual for anyone seriously interested in the subject. It
should be pointed out that this is not "light reading", and in fact assumes a
collegiate, or graduate level background in physics, chemistry, and math, on the
part of its reader. However, for anyone who is serious about wanting to become
involved in this area of research, this is the best reference manual to date
from which to get started. 
In the "Drexlerian" model of the nanoworld, the construction of nano components begins with the evolution and creation of "designer" molecules, with special geometries, bonding properties, and interactive potential features, a sort of "molecular lego set" to suit the task at hand. One might view the hierarchy of molecular subassemblies as being composed of various species, and classes of molecules, and molecular grouping sets. Why would such activity be interesting? Consider, for in stance, a construction process which has a resolution of approximately 0.1 nm (nanometer, or billionth of a meter). At this scale of manipulation, not only is the spatial domain compressed, but the temporal domain is compressed as well. For instance, there are defensible arguments for the theoretical construction of nanomechanical components which can operate at approximately 10(9) Hz, or mechanosynthesis of nanoconstructions (mechanically controlled molecular construction, or "shaping" of molecular structures) at 10(6) operations/device-second. In this domain, a theoretical molecular replicator, capable of "building" complex "macro objects" on demand, could have a potential construction rate of 1 kg/10(-4) second.
Consider the concept of "self-replicating" molecular sub structures, in which
the specific properties of a given resultant "macro-object" is the direct result
of a self regulating nano construction process. Aside from the obvious
implications of complex, nano replication and construction processes, consider
such exotic realms as nano logic gates which occupy a volumetric footprint of
10(-26) cubic meter, with a mechanical switching time of 0.1 ns. Indeed, in Dr.
Drexlers' vision of complex nanocomputing logic arrays, consisting of
nanomechanical gate constructions operating in the GHz bandwidth, a parallel
processing engine capable of 10(15) MIPS could fit into a matchbox, complete
with an appropriate power supply. 
In the realms of molecular computing, in which the relative "location" of an individual molecule (see sidebar on nanomechanical and molecular computing) between alternate "influence zones" determines the logical 1/0 status of a given gate site, the potential dimensions of space, time, and relative power dissipation compress even further. And of course, this doesn't even ac count for yet another realm of computing capability, the optical domain.
In fact, there are a number of researchers who are currently exploring the combination of both nano-electronic and optical computing components. Amongst various applications, this approach is of particular interest to those pursuing such technically daunting challenges as the construction of neural net processing engines, theoretically capable of approaching the elusive "high level reasoning" targeted by so many artificial intelligence researchers.
I feel the need, at this point, to reiterate the fact that though the above
mentioned topics are still very much in the research and development stage, this
is not science fiction. MIT's Dr. Marvin Minski, for instance, considered by
many to be one of leading "gurus" of artificial intelligence theory and
development, is extremely keen on these latest nanocomputing technologies, and
indeed, refers to Dr. Drexlers' book as "the book for starting the next century
of engineering". But machines that can actually think, reason, and learn, or
"intelligent" molecules that can instruct each other how to interconnect and
perform complex construction processes, is still only the beginning.
The potential bio-medical applications are not only far reaching, but in fact may permanently alter the definitions of life as we currently generally accept them. The very boundaries of philosophical, and perhaps, ethical questions concerning where "life" ends, and something else yet to be defined begins, are at best soon to become a very fuzzy gray zone of definitions. What do I mean by this statement?
Consider the current state of medical enhancements already available. In today's medical world, organ transplants, mechanical prosthesis applied as bone replacements, and other synthetic enhancements, are considered to be standard medical procedures. Furthermore, life support systems now exist which can extend physical life in an otherwise brain dead body indefinitely. Artificial sensory implants, such as the recently developed cochlear implant to restore sound perception to hearing impaired, or even totally deaf patients, are now being applied on a limited basis. Early stages of research are currently being conducted to eventually allow a direct electrical connection to optic nerve bundle sites, with the ultimate goal being to supply "visual" information to a blind person via an electronic camera or computer interface. Artificially grown skin cultures are currently being produced as a method to supply skin grafts to burn victims, or those suffering from extreme dermatological disorders. Research is continuing in several locations worldwide in development of an artificial heart. And this description of currently applied medical technology doesn't even include the exploratory realm of genetic research, in which gene modification and "screening" can be potentially applied to every aspect of medical application, from diseases to cosmetic features.
These examples are only a few of a litany of existing biomedical enhancements which have gradually been accepted by the majority of the general public as "normal" medical options to solve various problems and diseases. And yet, already many ethical and legal questions are mired in an ever changing set of rules and definitions, which place many doctors and institutions in a realm of uncertainty.
The next logical step is a further improvement of such life enhancing and life extending technologies to an ever increasing range of options and improvements. A fundamental shift in technologies is approaching where life expectancy, physical and mental abilities, and other permanent alterations to the human body via artificial "cybernetic" implants and nanoconstructions will make the current set of questions facing the medical world seem utterly trivial.
But just where does this realm end? In the upcoming nanorealm, it doesn't. For instance, some nanotech designers envision permanent "nanite" objects which can be injected or implanted into the human body to perform a seemingly endless variety of tasks. Examples already being researched are nanomechanical "scrubbers" which can swim through veins and arteries, cleaning out cholesterol and plaque deposits on a regular basis. At Carnegie Mellon University (Pittsburgh), nanomachines with rotor blades on the scale of a human hair are being constructed and studied with just this sort of application in mind.
Another example currently being investigated by Dennis Polla at the University of Minnesota is the possibility of a chemical sensing "intelligent" nanosystem, which contains all of the sensory, pumping, and mechanical components to provide a self regulating internal insulin dosage dispensing device. In fact, this same type of "nano-innoculant" could be used to supply a self regulated dose of any number of drugs, physiologically regulating compounds, etc.
But this is only the beginning, and a very small beginning at that. Much like the situation when the first laser was successfully demonstrated in 1956, no one then could have foreseen even a fraction of the incredible array of applications lasers are currently involved with. And yet, the example of the laser may only be minuscule compared to the much vaster potential of what the bio-medical implications of applied nanotechnology can consist of in the near future.
Starting with life extension oriented devices, consider a "fleet" of nanites which patrol throughout the human body, something like a nanomechanical and nanochemical artificial immune system, looking for "trouble". If an invader cell, or even a virus is detected, they can surround and "disable" the offending organism. For example, in the case of current day cancer treatments, often chemotherapy is applied to rid the body of unwanted cancer cells and tumors. The chemotherapy is essentially a controlled dose of chemical toxins, designed to kill the offending cells, but often the side effects of this type of systemic poisoning is almost as traumatic as the cancer itself, and is extremely unpleasant to the patient. By contrast, a nanite component designed for this purpose, injected into the human body, could seek out the offending cells via a chemical message sensory "pad", and apply a chemical "marker" to the offending cells. This would then allow for a vastly more precise targeting of an appropriate chemical toxin, which could also, of course, be administered by a nano-innoculant device.
But this is still only the beginning. In a much more far reaching implication, actual performance enhancement, rather than mere "repair" or maintenance, is a consideration currently being explored. In other words, the first stage of human nano implants would be to extend life, and continuously monitor and arrest various disorders as they occur. The next stage would be to "enhance" the life experience beyond what is currently possible.
The human brain is essentially a very complex electrochemical processing engine, with tactile and sensory input devices communicating to it. Within the brain itself are approximately 2 - 2.5 billion dendrite fibers, arranged in branching structures called ganglia. Each ganglionic cluster of dendrites responds to input voltage stimulus signals, which occur as sodium ions conducted into the individual dendrite fibers. The stimulated ganglion responds by producing a response stimulus voltage pattern, i.e., a secondary release of sodium ions, which in turn stimulates the surrounding ganglia through their dendrite fibers. The actual mechanics of the process is partially dependent on a voltage controlled membrane which surrounds each dendrite fiber. As the membrane is stimulated, the molecular porosity of this membrane increases, thus allowing a certain range of permeability to sodium ion transmission.
Research has shown that the robustness of information processing and storage is dependent on the relative dendrite fiber density (total exposed dendrite surface area) in a given region of brain tissue. Furthermore, neural net systems, as modeled on a computer, have shown that repeated exposure to a similar stimulus pattern tends to increase the robustness of the "learned" information stored in the corresponding portion of the network. Interestingly, recent experiments have indicated an actual physiological response to repeated electrical stimulus to dendrite fibers. The results are actual "buds" being formed on some of the dendrite branches within a given ganglion.
It has been considered by some theorists that at some point in the not too distant future, this electrochemical process can in fact be "enhanced" by the addition of highly specialized nanocomponents designed to increase, or alter, the rate of sodium ion transmission, and artificially regulate the activity of the voltage controlled membranes which are a key component in this process. The implications are far reaching indeed, considering that everything from basic sensory perception to actual information processing and high level reasoning, the very essence of "intelligence" as it is currently defined, may be altered by the implantation of these "neural enhancement" nano devices.
For years, biochemists and neurophysiologists have been investigating behavior modification and performance enhancement (so called "intelligence boosting") with drugs designed to make very subtle modifications in brain chemistry. The application of these types of nanocomponents could drastically alter the rate of progress in this domain, and in fact instigate areas of research never previously considered.
Dr. Erwin Neher (director of the department of membrane biophysics at the Max Planck Institute for Biophysical Chemistry in Gottingen) and Dr. Bert Sakmann (director of cell physiology at the department of biophysics at the Max Planck Institute for Medical Research in Heidelberg) shared the Nobel Prize for Physiology in 1991, for their pioneering work in identifying the exact nature in which this electrochemical process functions. In fact, they have successfully identified how many types of cells and cellular systems in the human body, aside from neural cells, utilize electrochemical signals to communicate and interact with each other (see sidebar on medical nanomechanics). This is an extremely crucial step in designing, and eventually constructing nanomechanical and nanochemical components which can target exact cell interactions, and modify their stimulus and response characteristics.
Another aspect of applied nanotechnology is the development of specialized materials which have unusual properties. This can range from the development of shape changing alloys which consist of metallic crystalline substrates whose state phase geometries can be triggered to switch as a function of input electrical or thermal stimulus (see the Sept/Nov '92 issue of M.E.), to so called "Bucky" balls and tubes of carbon with extraordinary structural characteristics, and capable of encasing other compounds, to warm temperature superconductors, and even inorganic substrates which can mimic the behavior of organic compounds. In short, this is, in my opinion, the true outer edge of where the science fiction of a few years ago is in fact occurring today in laboratories around the world.
In this realm of "nanochemical alchemy", researchers are beginning to look at solving difficult (if not formerly impossible) engineering problems, not by designing around the materials and processes currently available to them, but rather by conjuring up entirely new classes of materials demonstrating seemingly impossible characteristics to suit the task at hand. It is in this realm that the tools of nanostructure designers will be developed, and from which many of the already mentioned "higher order" nano systems will evolve.
For example, one of the more daunting problems facing designers of medical implant devices is the issue of biocompatibility. Many materials may demonstrate one or two specific properties, but trying to create a device which can remain slippery to some fluids but not others, interact with a very narrow or specific range of chemical "messengers", etc., present extremely difficult challenges to bioengineers. That is until the recent development of so-called "designer surfaces" using some very novel techniques.
What's even more interesting is that several companies are already offering these specialized surfacing techniques as a commercially available process. Perhaps the most interesting is the photoactivated reagent process developed by Bio-Metric Systems, Inc. of Eden Prairie, MN. What they have produced is a series of photoactivated reagents which can "capture" specific biomolecular structures and hold them in place. This in turn al lows these structures to be applied to an extraordinary range of surfaces, including metals, polymers, and other "synthetic" materials. This is a crucial step in designing future nanocomponents for internal medicine and cybernetic applications.
However, at a much more fundamental level of material development is the ongoing research into an array of carbon atom structures referred to as "fullerenes" (named after futurist Buckminster Fuller). Consider, for instance, attempting to en case atoms of elements which would otherwise never want to react with anything, or "stay put" for a given reaction event. Consider, for instance, a spheroid of carbon atoms, in an arrangement looking something like a soccer ball, encasing an atom of helium. Impossible, as most chemists would probably react?
In fact, it is not only possible, but has already been successfully demonstrated at Yale University. Martin Saunders, one of the primary researchers in this field at Yale, has been experimenting with a multistage process consisting of first creating an "environment" of spherical fullerenes by passing an electrical current through graphite electrodes in a helium filled chamber, and then "baking" the resulting molecular spheroids in a helium saturated furnace to further increase the relative population density of helium containing carbon spheroids in the resulting environment.
But the range of carbon fullerene molecular constructions goes far beyond containing "uncooperative" atoms. As a methodology for constructing "impossible" compounds, this area of re search opens up a realm of possibilities that would have simply been laughed at ten years ago. Whether the end result is to convince non-reactive chemical components to interact with each other, or to achieve the opposite goal, to "contain" reactive substances that would otherwise be too unstable or over-reactive to work with, the possibilities are almost endless.
In fact, the horizons of fullerenes have now extended to an entire range of "bucky blobs", shapes and structures, which often include the introduction of other cooperative elements such as nitrogen, to form huge, complex molecular forms capable of creating such materials as lanthium dicarbide, the worlds' first synthetic material harder than diamond (commercially developed and produced at SRI International in Menlo Park, CA), ceramic compounds capable of superconductivity, and ultra strong carbon fibers on a nanoscale which could create cybernetic and structural components with fantastic stress loading properties, just to mention a few.
The original pioneer of this area of research, who now provides commercial access to "custom" carbon and carbon compound fullerenes (for about $1000 per gram), is Dr. Richard Smalley, a physicists from Rice University. Though he is still at the forefront of this technology, he is not alone by any means. In fact, interest in fullerenes, particularly in applications aimed at developing semiconductive and superconductive substrates constructed with fullerene technology, is being aggressively pursued in Japan, with some very big players entering into the long term development arena. For instance, NEC has taken a particularly keen interest in area.
At the University of Arizona, "mega-fullerenes" containing over 400 atoms each have been successfully created, which opens up yet another panorama of potential applications involving highly complex molecular structures. So called "bucky-tube" structures begin to suggest the possibility of nanoscale structural components, with virtually indestructible strength and en durance characteristics. For designers of nanosubstructures requiring particularly extreme structural integrity, this development holds particular promise. Especially when combined with the ability to "contain" atomic components of other elements, such as flourine to provide molecular lubrication, or combinant metallic dopants to provide "molecular batteries", nanodesigners are quickly adapting to this new standard of molecular engineering.
In fact, in yet another medical application, cancer cells could be attacked by anti-body containing bucky balls, which "home in" on the offending cells via the chemical "signals" recognized by the antibodies. Once the bucky balls have attached themselves to the cancer cells, laser light optically conducted through a molecular scale light guiding fiber could energize oxygen molecules which would be in solution in the bloodstream that encounter the bucky ball conglomeration. The end result is that the oxygen absorbs the energy, and the reaction caused by this process would in turn rupture, and destroy, the cancer cells.
If all of this isn't fantastic enough to stimulate some level of general interest, consider the research currently under way at New York University, where DNA molecules are being considered as potential building blocks for constructing organic "logic units", in developing DNA computers. In this circumstance, DNA molecular "chunklets" are being formed into cubes, octahedrons, and other geometric forms, for this very purpose.
In fact, the enterprise of "handling" exact bits of DNA with atomic accuracy was demonstrated with considerable success by a research team in the Department of Chemistry, at the University of New Mexico. Armed with a scanning tunneling electron micro scope, or STM, considered by many nanotechnologists as the ultimate atomic "handling" tool, this research team has developed a technique for "coaxing" DNA snippets down molecular sized groves etched into a glass slide. The electrically charged tip of the STM serves as an electrical "tweezers", which can grab the end of an individual DNA strand, and stretch it out according to the needs of the DNA manipulation at hand. Since the DNA is a tightly wound helix structure, it can demonstrate a considerable amount of relative elasticity as the helix is stretched out over a given distance. In fact, this elasticity can be very accurately manipulated by varying the amount of charge applied (switching off the charge allows the DNA strand to "spring" back to its original configuration).
At the extreme outer edge of molecular manipulation, however, are those researchers who are using the STM to arrange individual molecules, and even single atoms, to create "molecular sculptures". The basic concept of the STM is that utilizes an extremely fine tipped tungsten needle, which is electrically charged. As the tip of this needle is brought to within a few microns of a given sample, a charge potential is reached in which electrons begin to "tunnel" from the tip to the sample surface. The rate of electron flow, i.e., current of this conducting "tunnel", is exactly dependent on the precise distance between the needle tip and the sample surface. Therefore, by maintaining constant current control, and linking this control to the vertical displacement of the needle tip, the relative positional orientation of the needle during a scan pattern can be used to construct a topographical "map" of the surface being scanned. Amazingly, the electron tunneling current, utilized as the control mechanism in a positional feedback circuit, is so exact that the resulting topographical features rendered are accurate to the individual atomic boundaries within a molecular substrate. This process allows researchers not only to "see" individual atoms residing in their molecular substrate, but also to manipulate them with similar accuracy.
The classic example of this sort of molecular sculpting was performed by Donald M. Eigler, at IBM's Almaden Research Center in San Jose, CA, where the IBM logo was spelled out with individual xenon atoms on a nickel surface. But in a much more relevant, and potentially revolutionary application, is the possibility of a molecular structure in which the position of an individual xenon atom becomes the switching mechanism for atomic scale memory, and logic gates. In a storage device constructed in this fashion, the entire library of Congress could theoretically fit on the surface of a single 12" disk, as opposed to the 250,000 disks required by the highest density optical storage disks available today.
But aside from molecular construction at the atomic level, there are also significant developments in the more traditional construction concept, that is, "carving" small pieces and structures out of a larger surrounding substrate. Using photolithography processes very similar to those used for fabricating ordinary integrated circuits, researchers at a variety of public and private facilities have created an array of ultraminiaturized motors, actuators, pumps, vibrating vanes, as well as a plethora of gears, pistons, and other mechanical components out of silicon, nickel, and other metallic substrates.
Various universities, such as the U. of Utah, U. of California at Berkeley, and the U. of Wisconsin have long been involved with creating these micromechanical components since the beginning stages of this area of research. However, serious commercial research efforts are now being pursued by corporate concerns both here and abroad. Toshiba, for instance, now manufactures an etched substrate micromotor under 1mm(3), powered by a 1.7 volt DC power source. Interestingly, it can provide shaft rotations ranging from 60 to 10,000 RPM.
There are, however, other approaches to constructing these micromechanical components being investigated. Ralph Merkle, from the Xerox Research Center in Palo Alto, CA., is investigating the application of microthin diamond films as a mechanical substrate. Interestingly, the application of molecular sputtered diamond films was initially investigated as a method for creating a type of heat sink for extremely large, credit card size "megachips", by manufacturers such as TRW.
In parallel to this type of research, development of fabrication techniques for nanoscale conductors and "wires" is well under way. At the Centre d'Elaboration des Materiaux et d'Etudes Structurales, France, researchers have succeeded in producing an incredible array of gold conductors under 50nm wide and 15nm thick, embedded in a SiO2 substrate. Even more amazing is the topographical feature difference between the substrate and conductors can be maintained to within 2.2 nm. Perhaps most significant of all is that despite the extremely small feature size of these conductors, which the experimenters have created from gold and gold palladium alloys, the average resistance of a "nanoconductor" at room temperature was maintained to about 60 ohms.
The concept of nanoscale "circuit boards", complete with embedded nanoelectronic components, is shifting out of the "vision of the future" realm, and into the component development and design stage.
But perhaps the most intriguing aspect of the upcoming nanorealm is not just the fabrication of nanomechanical, and nanoelectronic components, but the actual construction of "self replicating" molecular structures. The concept here is that nanite components may be developed to a circumstance where they can "assemble" themselves at the molecular level, and more importantly, be able to disassemble and reassemble according to the situational circumstances of their surroundings. Even this seemingly fantastic boundary has already been probed. At MIT, researching chemist Dr. Julius Rebek has already demonstrated several "self replicating" molecules, where molecular subcomponents interact to form secondary and tertiary compounds. As the secondary stage compound is formed, the recombination of these "molecular subcomponents" eventually end up producing complete chemical clones of the original molecule. According to Dr. Rebek, this basic principal can be applied to both organic and inorganic molecules. Behaving very much like a three dimensional molecular lego set, the self replication process is directly dependent on the complementary shapes of the interconnecting molecular components that are assembled in the replication process.
All of the topics covered in this article are only a brief summary of a much larger realm of technical development. Profound as this new "nano-revolution" is, how it will eventually filter into and affect the life of the average population could have several different outcomes. Not the least of the considerations here is an unfortunately dismal level of basic technical and scientific illiteracy on the part of the general public, and a tendency to panic, or react irrationally to even fairly simple technical developments.
After all, how will a public which blindly panics over the "threat" of getting brain cancer from using cellular telephones, or goes into a complete frenzy over a minor genetic alteration to a commercial food crop (as if genetic alterations haven't been occurring since life first began on this planet!), respond to the concept of cybernetically enhanced humans, life extending artificial implants, truly synthetic "organisms", machines that can think and reason, and so on. One thing is absolutely certain, however. Whether the nano-revolution occurs here, or elsewhere in the world, the evolution of this new technology is inevitable. I can only hope that the developmental, and socio-economic future of this country isn't squandered stupidly because of ignorance, and irrational panic, but rather is harnessed and applied in the most productive ways possible.
About the author: Charles Ostman has spent the past 20+ years involved with electronics, computers, and physics, including 8 years at Lawrence Berkeley Laboratory at the U. of California, Berkeley, where he had the opportunity work with some of the early pioneers in specialized materials development, including shape changing alloys. He is currently a member of Nanothinc (San Francisco, CA), a recently formed "think tank" which is in the process of establishing a nanotechnology data base, various educational and entertainment oriented materials, and other projects concerning nanotechnology applications.