INSIDE TRACK: Material benefits from mighty molecules: NANOTECHNOLOGY: Most man-made materials come from heating, grinding and crushing. But scientists can instil them with remarkable properties by building them atom by atom, writes Fiona Harvey
Financial Times; Aug 7, 2001
By FIONA HARVEY
globalarchive.ft.com.
When Zacharias Janssen looked through the first compound microscope at the end of the 16th century, he began a fascination with the workings of the world that we cannot see.
Microscope technology has come a long way since that primitive two- lensed device. Now we can see into the finest structure of materials and examine the behaviour of individual atoms. We can look at how substances fit together and see in reality what chemists had known before only in theory. And by shaping how things are formed at a fundamental level, scientists can create a whole new class of substance: nanomaterials.
Horst Stormer, the Nobel prize-winning researcher at Lucent Technologies' Bell Labs, offers a sense of what may lie ahead: "(Science has) given us the tools . . . to play with the ultimate toy box of nature - atoms and molecules. Everything is made from (them). The possibilities to create new things appear limitless."
Nanomaterials are substances whose make-up can be determined with extreme accuracy. A nanometre is a billionth of a metre - one 100,000th the width of a human hair. By careful chemical and physical manipulation, scientists have learnt to control the structure of certain materials at the nanometre scale, which is almost to manipulate individual molecules.
Such materials have been in development for some years in start-up companies, many of them spin-offs from universities. These companies are beginning to have a commercial impact. The market for nanomaterials has been estimated at between Dollars 5bn (Pounds 3.5bn) and Dollars 10bn in the next 10 years, as the technology finds new applications in a variety of fields, from new types of sun-cream to computer screens and super-sharp knives.
Strictly, a nanomaterial is one in which the structure is controlled to a level smaller than 100 nanometres. Inevitably, though, a prefix as futuristic-sounding as "nano" has been interpreted fairly loosely in materials science, as in other branches of technology. It is sometimes used to describe bigger, "micro" materials that are measured in mere millionths of a metre.
Nanomaterials have many advantages. Where conventionally produced materials tend to be gross and irregular in composition, with many flaws, nanomaterials approach an elegant perfection. By defining the structure of a substance on such a small scale, scientists can create satisfyingly regular and even flawless shapes.
"Only by growing (them) can you make perfect crystals every time," says Dr Gareth Wakefield, who is head of research at Oxonica, a UK company spun off from Oxford University.
Growing materials from scratch improves the efficacy of the final product in applications where the shape of the particle is crucial. For instance, one German company, Gesellschaft fur Diamantprodukte, has created a scalpel made of diamond, grown on a nano scale on silicon. Its edges can be made many times sharper than ordinary scalpels because the crystals have been built up rather than ground down.
Nanomaterials can similarly be used in the manufacture of computer screens to improve picture quality. Nanoengineered particles of inorganic materials exhibit greater optical, magnetic and electrical properties than normal, imperfect particles.
Oxonica has found a way to grow, by a process known to chemists as "colloidal precipitation", phosphor particles of a more perfect shape than conventionally manufactured phosphors, which are created by smashing up lumps of the substance. Normal tele-vision or computer screens need an electron gun powered by 30,000 volts to induce the phosphors to shine, because of the roughness of the surfaces of the smashed-up phosphor. Oxonica has demonstrated that its perfectly shaped phosphors can be much more efficient, requiring electron guns powered by only 500 volts.
Nanomaterials, being more finely structured, are smoother and, when in powder form, have a greater surface area than conventionally produced compounds. So nanomaterials also have a promising future in paint and coatings and in catalysis, where molecules come together on a surface to react.
"Catalysis is a very important application, because nanomaterials can have a 30 per cent greater surface area than conventionally made substances," says Tim Harper, chief executive of CMP-Cientifica, a nanotechnology consultancy. In medicine, too, drug delivery could be improved by the application of nanotechnology, as drugs with a large surface area would be absorbed more quickly by the body.
Stephan Mietke, of the microtechnology innovation team at Deutsche Bank, points to medical applications in prosthetics, where films of nanoparticles can be used to coat joints. This gives a less abrasive surface coating, which leads to less wear and tear in the joint.
Nanomaterials could even be used in future to help to give protection against environmental pollution. At the Sandia National Laboratories, a US government-funded research institution, Jeff Brinker is working on a form of smart membrane that would enable the filtering of substances at a molecular level.
Dr Brinker, a nanotechnologist, has produced an ultra-thin coating with a large surface area and a totally regular nanostructure. It has pores designed to admit molecules of a particular size and can thus be used as a chemical sensor to detect molecules to a degree of sensitivity 500 times greater than that of conventional materials.
Dr Brinker's research points the way to "smart" membranes that would open and close their pores depending on the molecule approaching them, thus cleaning air or water of environmental pollutants.
Advances in microscopy were the first key to developing materials on a nano scale. As Mr Harper points out drily: "It helps to be able to see what you're doing." The invention of technologies such as the scanning-tunnelling microscope spurred on research into the atomic structure of substances and how to exploit it.
Our increasing understanding of physics and chemistry has helped, too. For instance, colloidal precipitation, one of the main processes used in manufacturing modern materials, had its origins in the work of Michael Faraday in the 19th century but has only now been brought to a stage where it can be used in industry.
For all the improvements in our theoretical expertise, however, nothing commercial could have come of this research without sheer hard slog in factories. "It took us 10 years and Dollars 40m to come up with a method (of producing nanomaterials)," notes Don Freed, vice-president of business development at Nanophase Technologies in the US.
Engineering techniques had to be found to deal with substances being made at such a fine level. The manufacturing processes for nano-materials often require an unprecedented degree of accuracy, which in turn requires ultra-fine tools and machinery.
Nanophase makes aluminium oxide that is used in sunscreen cream, in little spheres of about 40 nanometres in diameter. "(To make them,) you need very controllable conditions and a combination of expertise in physics and manufacturing," says Dr Freed.
As these processes are refined, we can look to the extension of nano- materials into new areas, such as the car industry, where nanostructures could be used to create new plastics that are lighter but stronger than aluminium.
However, the demands of precision engineering are likely to confine the materials to specialised uses. Dr Wakefield believes the process will be limited to substances used by manufacturers in quantities of a few hundreds of tonnes, at prices measured perhaps in dollars per kilogramme. After all, while nanomaterials may prove invaluable in making medical prostheses, it is unlikely ever to be necessary to nano- engineer a house brick.
Copyright: The Financial Times Limited |
