Wednesday, 20 July 2011
The Meaning of Nanotechnology
The Meaning of Nanotechnology
When K. Eric Drexler (right) popularized the word 'nanotechnology' in the 1980's, he was talking about building machines on the scale of molecules, a few nanometers wide—motors, robot arms, and even whole computers, far smaller than a cell. Drexler spent the next ten years describing and analyzing these incredible devices, and responding to accusations of science fiction. Meanwhile, mundane technology was developing the ability to build simple structures on a molecular scale. As nanotechnology became an accepted concept, the meaning of the word shifted to encompass the simpler kinds of nanometer-scale technology. The U.S. National Nanotechnology Initiative was created to fund this kind of nanotech: their definition includes anything smaller than 100 nanometers with novel properties.
Much of the work being done today that carries the name 'nanotechnology' is not nanotechnology in the original meaning of the word. Nanotechnology, in its traditional sense, means building things from the bottom up, with atomic precision. This theoretical capability was envisioned as early as 1959 by the renowned physicist Richard Feynman.
I want to build a billion tiny factories, models of each other, which are manufacturing simultaneously. . . 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. — Richard Feynman, Nobel Prize winner in physics
Based on Feynman's vision of miniature factories using nanomachines to build complex products, advanced nanotechnology (sometimes referred to as molecular manufacturing) will make use of positionally-controlled mechanochemistry guided by molecular machine systems. Formulating a roadmap for development of this kind of nanotechnology is now an objective of a broadly based technology roadmap project led by Battelle (the manager of several U.S. National Laboratories) and the Foresight Nanotech Institute.
Shortly after this envisioned molecular machinery is created, it will result in a manufacturing revolution, probably causing severe disruption. It also has serious economic, social, environmental, and military implications.
A basic definition: Nanotechnology
What is Nanotechnology?
| A basic definition: Nanotechnology is the engineering of functional systems at the molecular scale. This covers both current work and concepts that are more advanced. In its original sense, 'nanotechnology' refers to the projected ability to construct items from the bottom up, using techniques and tools being developed today to make complete, high performance products. |  |
Saturday, 16 July 2011
Laser trapping of erbium
Laser trapping of erbium
Physicists at the National Institute of Standards and Technology (NIST) have used lasers to cool and trap erbium atoms, a "rare earth" heavy metal with unusual optical, electronic and magnetic properties. The element has such a complex energy structure that it was previously considered too wild to trap. The demonstration, reported in the April 14 issue of Physical Review Letters,* might lead to the development of novel nanoscale devices for telecommunications, quantum computing or fine-tuning the properties of semiconductors.
Laser cooling and trapping involves hitting atoms with laser beams of just the right color and configuration to cause the atoms to absorb and emit light in a way that leads to controlled loss of momentum and heat, ultimately producing a stable, nearly motionless state. Until now, the process has been possible only with atoms that switch easily between two energy levels without any possible stops in between. Erbium has over 110 energy levels between the two used in laser cooling, and thus has many ways to get "lost" in the process. NIST researchers discovered that these lost atoms actually get recycled, so trapping is possible after all.
The NIST team heated erbium to over 1300 degrees C to make a stream of atoms. Magnetic fields and six counter-propagating purple laser beams were then used to cool and trap over a million atoms in a space about 100 micrometers in diameter. As the atoms spend time in the trap, they fall into one or more of the 110 energy levels, stop responding to the lasers, and begin to diffuse out of the trap. Recycling occurs, though, because the atoms are sufficiently magnetic to be held in the vicinity by the trap's magnetic field. Eventually, many of the lurking atoms fall back to the lowest energy level that resonates with the laser light and are recaptured in the trap.
The erbium atoms can be trapped at a density that is high enough to be a good starting point for making a Bose-Einstein condensate, an unusual, very uniform state of matter used in NIST research on quantum computing. Cold trapped erbium also might be useful for producing single photons, the smallest particles of light, at wavelengths used in telecommunications. In addition, trapped erbium atoms might be used for "doping" semiconductors with small amounts of impurities to tailor their properties. Erbium--which, like other rare earth metals, retains its unique optical characteristics even when mixed with other materials--is already used in lasers, amplifiers and glazes for glasses and ceramics. Erbium salts, for example, emit pastel pink light.
Genetics Today
Genetics Today
Genetics began by being ignored. Now it has the opposite problem. Mendel was dismissed because his work seemed unimportant, but today genes are everywhere and the public is fascinated by their promises and disturbed by their threats. Scientists have been quick to emphasize both. Not for nothing has it been said that the four letters of the genetic code have become H, Y, P and E.
The last decade's advances have been amazing. We have the complete sequence of the DNA letters of the 60,000 or so working genes needed to make a human being, and will soon have that of all the so-called "junk" DNA sequence (which may reveal that it does more than its name implies). 10,000 different diseases have an inherited component, and - in principle at least - we know the genes involved.
That raises both hopes and fears. For diseases controlled by single genes, such as sickle-cell anaemia or cystic fibrosis, it has become easier to identify both carriers and foetuses at risk. Because any gene can be damaged in many ways - for example, there are more than 1,000 known mutations for cystic fibrosis - the tests are not straightforward, and often the best that will be possible is to tell people that they are carriers, rather than to reassure them that they are not. The decisions as to whether to become pregnant or to continue with a pregnancy will, however, become somewhat easier as the tests become less ambiguous.
Tests are commercially available for genes predisposing to cystic fibrosis and breast cancer; and the development of DNA "chips" that can screen many genes at once means that more will soon be on sale. Medicine will have to deal more and more with those who have - rightly or wrongly - diagnosed themselves as at risk.
Most people, we now realize, die of a genetic disease, or at least of a disease with a genetic component. For some, it will become possible to tell them of their plight - but why should we want to do so? Sometimes, the information is helpful. Those who inherit a disposition towards certain forms of colon cancer, for example, can be helped by surgery long before the disease appears. For other illnesses, people at high risk can be warned to avoid an environment dangerous to them. Smoking is dangerous, but a few smokers get away with it. However, anyone who carries a changed form of an enzyme involved in clearing mucus from the lungs will certainly drown in their own spit if they smoke - and that might be enough to persuade them not to. However, knowledge can be dangerous, particularly when health insurance gets involved.
The most successful kind of medicine has always been prevention rather than cure. Genetics is no different, and the hope of replacing damaged DNA by gene therapy is still around the corner, where it has been for the past ten years. Genetic surgery - the ability to snip out pieces of DNA and move them to new places - has done remarkable things, but so far has done little to cure disease.
It might, though, help prevent the world's population from starving, at least according to enthusiasts for genetically modified (GM) foods. They may be right. It has proved remarkably easy to move plant genes around. Already there are crops that have been altered to make them resistant to parasites, or to artificial weedkillers (which means that the fields can be sprayed, leaving the crop unharmed). Commercial optimism has, in Europe if not the United States, been matched by public concerns about health risks. Why people are worried by the remote risk that GM foods might be dangerous to eat when they are happy to eat cheeseburgers that definitely are, mystifies scientists, but science is less important than what consumers are willing to accept. Unless attitudes change, the hope of putting genes for, say, essential nutrients into Third World crops will probably not be fulfilled.
If interfering with plants alarms society, to do the same with animals outrages a vocal part of it. We still know rather little about how a fertilized egg turns into an adult, with hundreds of different kinds of tissue, each bearing exactly the same genetic message but with jobs as different as brain cells and bone. Although it has long been possible to grow adult plants and even frogs from single cells, the notion that it might be possible to do so with mammals seemed a fantasy - until the birth of Dolly the sheep in 1997. Then, with the simple trick of inserting the nucleus from an adult cell into an emptied egg and allowing it to develop inside a foster-mother, a sheep was made without sex: it was cloned.
Cloned sheep or cows might be important in farming, and might be used to make multiple copies of animals with inserted human genes for proteins such as growth hormone (which are already used in "pharming", the production of valuable drugs in milk). The publicity that followed Dolly led to immediate condemnation of the idea of human cloning, often without much thought as to quite why it should be so horrific. After all, we are used to identical twins (who are clones of each other), so why should an artificial version cause such horror? In the end, again, public opinion moulds what science can do, and the prospect of cloning a human being seems remote.
And why might anyone want to do it? Claims of an army of identical Saddam Husseins verge on the silly, and others of replicating a loved child who died young also seem unlikely. However, the technique has great promise in medicine. Cells of the very early embryo (stem cells, as they are called) have the potential to divide into a variety of tissues, and can be grown - cloned - in the laboratory, or even manipulated with foreign genes. Perhaps they could make new skin or blood cells, or, in time, even whole organs. Because this involves the use of very early embryos, made perhaps by artificial fertilization in the laboratory and not needed for implantation into a mother, it has become mixed up with the abortion debate. In the United States, the "Pro-Life" lobby has succeeded in denying funds from government sources for such work.
Genetics is always mixed up with politics. It has been used both to blame and to excuse human behaviour. The claim (in the end not confirmed) of a "gay gene" led to two distinct responses among the homosexual community. Some feared that the gene would be used to stigmatize them, but most welcomed the idea that their behaviour might be coded into DNA, as it meant that they could not be accused of corrupting those not already "at risk". Such opposing views apply just as much to the supposed genes that predispose to crime - are they evidence that the criminal cannot be reformed and must be locked away for ever, or should they be used in mitigation to argue that he was not acting according to his own free will?
Science has no answer to such questions, and in the end the most surprising result of the new genetics may be how little it tells us about ourselves.
Nanotechnology Manufactured products
Nanotechnology
Manufactured products are made from atoms. The properties of those products depend on how those atoms are arranged. If we rearrange the atoms in coal we can make diamond. If we rearrange the atoms in sand (and add a few other trace elements) we can make computer chips. If we rearrange the atoms in dirt, water and air we can make potatoes.
Todays manufacturing methods are very crude at the molecular level. Casting, grinding, milling and even lithography move atoms in great thundering statistical herds. It's like trying to make things out of LEGO blocks with boxing gloves on your hands. Yes, you can push the LEGO blocks into great heaps and pile them up, but you can't really snap them together the way you'd like.
In the future, nanotechnology will let us take off the boxing gloves. We'll be able to snap together the fundamental building blocks of nature easily, inexpensively and in almost any arrangement that we desire. This will be essential if we are to continue the revolution in computer hardware beyond about the next decade, and will also let us fabricate an entire new generation of products that are cleaner, stronger, lighter, and more precise
It's worth pointing out that the word "nanotechnology" has become very popular and is used to describe many types of research where the characteristic dimensions are less than about 1,000 nanometers. For example, continued improvements in lithography have resulted in line widths that are less than one micron: this work is often called "nanotechnology." Sub-micron lithography is clearly very valuable (ask anyone who uses a computer!) but it is equally clear that lithography will not let us build semiconductor devices in which individual dopant atoms are located at specific lattice sites. Many of the exponentially improving trends in computer hardware capability have remained steady for the last 50 years. There is fairly widespread confidence that these trends are likely to continue for at least another ten years, but then lithography starts to reach its fundamental limits.
If we are to continue these trends we will have to develop a new "post-lithographic" manufacturing technology which will let us inexpensively build computer systems with mole quantities of logic elements that are molecular in both size and precision and are interconnected in complex and highly idiosyncratic patterns. Nanotechnology will let us do this.
When it's unclear from the context whether we're using the specific definition of "nanotechnology" (given here) or the broader and more inclusive definition (often used in the literature), we'll use the terms "molecular nanotechnology" or "molecular manufacturing."
Whatever we call it, it should let us:
* Get essentially every atom in the right place.
* Make almost any structure consistent with the laws of physics and chemistry that we can specify in atomic detail.
* Have manufacturing costs not greatly exceeding the cost of the required raw materials and energy.
There are two more concepts commonly associated with nanotechnology:
* Positional assembly.
* Self replication.
Clearly, we would be happy with any method that simultaneously achieved the first three objectives. However, this seems difficult without using some form of positional assembly (to get the right molecular parts in the right places) and some form of self replication (to keep the costs down).
The need for positional assembly implies an interest in molecular robotics, e.g., robotic devices that are molecular both in their size and precision. These molecular scale positional devices are likely to resemble very small versions of their everyday macroscopic counterparts. Positional assembly is frequently used in normal macroscopic manufacturing today, and provides tremendous advantages. Imagine trying to build a bicycle with both hands tied behind your back! The idea of manipulating and positioning individual atoms and molecules is still new and takes some getting used to. However, as Feynman said in a classic talk in 1959: "The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom." We need to apply at the molecular scale the concept that has demonstrated its effectiveness at the macroscopic scale: making parts go where we want by putting them where we want!
The requirement for low cost creates an interest in self replicating manufacturing systems, studied by von Neumann in the 1940's. These systems are able both to make copies of themselves and to manufacture useful products. If we can design and build one such system the manufacturing costs for more such systems and the products they make (assuming they can make copies of themselves in some reasonably inexpensive environment) will be very low.
Nanotechnology
Nanotechnology is a technology based on the manipulation of individual atoms and molecules to build structures to complex, atomic specifications.
While many definitions for nanotechnology exist, DFI concurs with the National Nanotechnology Initiative (1) definition, which denominates "nanotechnology"; only if it involves all of the following:
The nanoscale is about a thousand times smaller than micro that is, about 1/80,000 of the diameter of a human hair. Approximately 3 to 6 atoms can fit inside of a nanometer, depending on the atom. The prefix nano means ten to the minus ninth power, or one billionth. Nanoscale technologies are the development and use of devices that have a size of only a few nanometers.
Nanotechnology has the potential to profoundly change our economy and to improve our standard of living, in a manner not unlike the impact made by advances over the past two decades by information technology.
Numerous products featuring the unique properties of nanoscale materials are available to consumers and industry today. Nanotechnology is used in electronic, magnetic and optoelectronic, biomedical, pharmaceutical, cosmetic, energy, chemical-mechanical polishing, magnetic recording tapes, sunscreens, automotive catalyst supports, biolabeling, electroconductive coatings and optical fibers.
Although the main applications of Nanotechnology have been developed in the computer and electronics fields, some other current uses that are already in the marketplace include:
While many definitions for nanotechnology exist, DFI concurs with the National Nanotechnology Initiative (1) definition, which denominates "nanotechnology"; only if it involves all of the following:
- Research and technology development at the atomic, molecular or macromolecular levels, in the length scale of approximately 1 - 100 nanometer range.
- Creating and using structures, devices and systems that have novel properties and functions because of their small and/or intermediate size.
- Ability to control or manipulate on the atomic scale.
The nanoscale is about a thousand times smaller than micro that is, about 1/80,000 of the diameter of a human hair. Approximately 3 to 6 atoms can fit inside of a nanometer, depending on the atom. The prefix nano means ten to the minus ninth power, or one billionth. Nanoscale technologies are the development and use of devices that have a size of only a few nanometers.
Nanotechnology has the potential to profoundly change our economy and to improve our standard of living, in a manner not unlike the impact made by advances over the past two decades by information technology.
Numerous products featuring the unique properties of nanoscale materials are available to consumers and industry today. Nanotechnology is used in electronic, magnetic and optoelectronic, biomedical, pharmaceutical, cosmetic, energy, chemical-mechanical polishing, magnetic recording tapes, sunscreens, automotive catalyst supports, biolabeling, electroconductive coatings and optical fibers.
Although the main applications of Nanotechnology have been developed in the computer and electronics fields, some other current uses that are already in the marketplace include:
- Stain-free clothing
- Coatings for easier cleaning of glass surfaces
- Bumpers and catalytic converters on cars
- Protective and glare-reducing coatings for eyeglasses and cars
- Sunscreens and cosmetics
- Longer-lasting tennis balls
- Light-weight, stronger tennis racquets
- Ink
- Water filtration
- Step assists on vans
- conduct R&D to realize the full potential of this revolutionary technology;
- develop the skilled workforce and supporting infrastructure needed to advance R&D;
- better understand the social, ethical, health, and environmental implications of the technology; and,
- facilitate transfer of the new technologies into commercial products.
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