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nanoscience : Conquering the Infinitely Small
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Conquering the Infinitely Small
Achievements and Promises of the Nanotechnology Revolution
by Philippe Mercure, translated by Timothy Barnard

To remake the world on an atomic scale: this is the mission that nanotechnology, the science of the infinitely small, has set for itself. The technological revolution is in motion, and it promises to radically alter medicine, electronics, and the various branches of engineering.

Pull a hair out of your head and hold it between your fingers. It's so thin that it's difficult to manipulate with your hands. Now imagine cutting this hair into a hundred thousand equal parts. Not crosswise, but lengthwise, where it is so thin. You would then have slices of hair around one nanometre thick. A nanometre is one-millionth of a millimetre; it belongs to another world - that of atoms and molecules. The laws of physics, which govern matter on a human scale, no longer apply here. If we were one nanometre tall, an atom of hydrogen would appear the size of a small ball, and a red corpuscle would appear bigger than Mount Everest. It is this seemingly inaccessible world that nanotechnology has set out to conquer over the past few years. And already there are tangible results in a host of fields.

New Materials, Made to Measure
To understand how nanotechnology is presently in the process of revolutionizing materials, think of two objects: a pencil lead and a diamond. While the former is black, dirty, and crumbly, the diamond is translucent and harder than any other material. And yet both objects are made of pure carbon. How can the same element generate such different properties? The answer lies in the fact that the way atoms are arranged on the scale of the infinitely small dramatically influences a material's properties. Herein lies nanotechnology's ambition: to modify the microscopic structure of matter in order to extract materials with new properties.

Here's a simple example: copper composed of crystalline particles fifteen nanometres in size is three times more resistant than copper composed of fifty-nanometre particles. It is also more malleable. No more evidence was required to inspire industry to set to work producing all sorts of materials in the form of nanoparticles. When combined or introduced into existing materials, such nanoparticles yield astonishing results. Plastic nanoparticles have made it possible to design automobile bumpers sixty per cent lighter and twice as resistant to scratching. Metal nanocrystals that better absorb light improve the performance of solar cells, bringing new hope to advocates of renewable energy. Tennis balls that last twice as long, fuel for space shuttles that burns twice as efficiently, stain-resistant pants made of nanofibres that repel dirt: these are some of the small revolutions that this technology has already brought us.

Giving the Human Body a Helping Hand
This new technology of the infinitely small has also given rise to promising applications in the field of medicine. The company AngstroMedica, for example, has patented a material for producing synthetic bone. By assembling the two components of bone (calcium and phosphate) at the molecular level the company has succeeded in reproducing the composition of natural bone. This advance will help in the treatment of bone fractures and disease.

Nanotechnology is even present in the food we eat. Some vitamins are not soluble in water, but when they are produced in the form of nanoparticles, they can be mixed with water and consumed as a beverage. Several brands of lemonade and fruit juice contain these sorts of nanovitamins. Nanoparticles have also been introduced into sunscreen in order to block UV rays. The small size of the particles means the cream does not become opaque.

Miniature Biology Laboratories
Biochips are undoubtedly one of the nanotech applications which will have the greatest impact. Biochips use the principle of DNA hybridization to detect genes, microbes, and other biological agents. We know that DNA is made up of two complementary molecular stems which join to form a double helix. The idea involves fixing one DNA stem onto a biochip - a stem whose sequence is known and which will serve as a probe. Then the biochip is sent out on patrol in a given environment. If the stem complementary to the probe is present in the area, the two stems will spontaneously reform the double helix, and the agent being sought will be detected. Up to several tens of thousands of probes can be placed on a biochip one centimetre square. The possibilities are extremely interesting: biochips can be used to detect microbes or other pollutants in potable water, to search for specific genes in the human body, to identify the genes involved in a medication's effectiveness, and so on. Biochips are already beginning to be marketed, and their use will quickly spread.

Seeing, Healing, and Mending Better
It is difficult to predict how the technology of the infinitely small will influence the medical world within the next few years. Some people are already imagining armies of miniature robots patrolling the human body to mend tissue, eliminate tumours, and release medication. If all that appears quite far off, it is true that some advances have the air of science fiction. The Israeli company Given Imaging, for example, has invented a mini-camera which can be placed inside a pill and swallowed to film the digestive system. Some research groups have also succeeded in creating microscopic tubules which can pierce the membranes of cells, thereby opening the door to the destruction of cancerous ones.

New Carbon Structures
Carbon is a fascinating element. Until quite recently, we knew of only two forms: the graphite in pencils, and diamonds (the two objects we used earlier to illustrate how the arrangement of atoms can influence a material's properties). In 1985, an astonishing new structure was discovered: a hollow sphere made up of sixty carbon atoms arranged in twelve pentagons - in short, the exact structure of a soccer ball, but on a nanometric scale. The new molecule was named Buckminsterfullerene, after Buckminster Fuller, an architect known for his similarly shaped building structures (geodesic domes). It was quickly discovered that these buckyballs, as they have been nicknamed, are the most common and most famous members of a family of molecules that can include up to 540 carbon atoms, generally known as fullerenes. These new forms of matter initially produced a great deal of curiosity in the scientific community. Then, in 1991, the Japanese scientist Sumio Iijima discovered something even more astonishing while synthesizing fullerenes: carbon atoms in the form of long hollow tubes. Curiosity quickly became enthusiasm, and the phrase carbon nanotubes was on everyone's lips.

Carbon Nanotubes
Carbon nanotubes are one of the great stars of nanotechnology, and for good reason. They are up to one hundred times more rigid than steel, and six times lighter. Designers are delighted with them, and have come up with a thousand and one uses for these little marvels. In addition to their extraordinary mechanical qualities, nanotubes have unique electrical properties. They are the only known material able to function as either conductors or semi-conductors, depending on their geometry. When we realize that the electronic circuits in computers are assemblages of conductors and semi-conductors, we may understand the great potential of these new materials - especially because nanotubes are quite simply the best conductors of electricity known.

Only one shadow hangs over this promising picture: despite extensive research, we still haven't found a way to produce carbon nanotubes in adequate quantities. At US $1500 per gram, they are more expensive than gold and, for the moment, not cost efficient enough for commercial use.

Nanotechnology to the Rescue of Microelectronics?
There is nothing surprising about the electrical circuit industry's interest in carbon nanotubes. Indeed, if there is one industry where miniaturization has been the watchword for a long time, it is microelectronics. In 1965, Gordon Moore, the co-founder of Intel, predicted that the number of transistors contained in integrated circuits would double every eighteen months. This is a prediction that the industry has almost exactly fulfilled for nearly forty years - we can now place 125 million transistors on a small wafer 112 millimetres square. But miniaturization will soon encounter a brick wall, because conventional transistors can not be reduced in size beyond a certain threshold without losing their effectiveness. It is now predicted that this technological barrier will be reached around the year 2018. An alternative to conventional integrated circuits must thus be found, and people are turning to nanotechnology for the solution. Of the candidates presently being considered for the job, molecular electronics is particularly interesting.

The idea behind molecular electronics is both simple and ambitious. The objective is to use the elementary building blocks of matter - atoms and molecules - to build tomorrow's integrated circuits piece by piece. The first molecular transistor made out of a carbon nanotube has already been made by scientists at IBM. Better yet, they have created a complete logic circuit on this nanotube. This, of course, is a great step forward, but it raises important questions: in this case nanotechnology is a victim of its own success, its infinite smallness. Constructing a transistor by moving one molecule at a time is all well and good. The question is, how to proceed when it comes to manufacturing the 125 million transistors required for a single Pentium 4? This is probably the greatest challenge facing nanotechnology today.

How to Remake the World Atom by Atom
There are two ways to work with matter on the level of the infinitely small. The first - the one used in the vast majority of technological applications carried out to date - consists of taking a unit of matter and then sculpting it, breaking it down and cutting it up to produce miniature structures. This is known as the top-down approach: proceeding from the large to the small.

Molecular electronics is an example of a second and different approach, which sets out literally to construct nanometric structures out of smaller units. This is the bottom-up approach: moving from the small to the large. In 1990, scientists achieved the feat of writing the IBM logo at nanoscale with thirty five xenon atoms. Atoms can be manipulated in this way by high-technology tunnel effect microscopes and atomic force microscopes. But these instruments have their limits: each movement of an atom can take several minutes. Even with devices capable of moving a million atoms per second, it would take an amount of time equivalent to the age of the universe to construct a sheet of paper! The challenge is to find a way of assembling the phenomenal qualities of atoms and molecules in a reasonable amount of time. Scientists are presently working on nanorobots which might do this work. Others are looking more towards self-assemblage, where atoms and molecules would join up by themselves according to an established plan. For example, by adding charged molecules to the surface of carbon nanotubes, it has been possible to align them on a plate containing patterns of an opposite charge.

Nature, which has organized hallucinatory quantities of molecules to form all kinds of living beings, commands admiration in the realm of assemblage. Perhaps we will find, in nature, solutions to the challenges that nanotechnology confronts today. In the meantime, the repercussions of this new science will continue to transform wide areas of human activity. It has only just begun.

Philippe Mercure holds a Bachelor of Science in Physical Engineering from the École Polytechnique de Montréal, and is presently completing a master's degree in opto-electronics at the same institution. He has worked as a research assistant at the Helsinki University of Technology in Finland, and is the recipient of the 2003 Fernand Seguin award for scientific journalism. He is currently working as an assistant on the Radio-Canada television program Découverte.

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