The need for molecular-scale manufacturing is turning towards commercial carbon-based electronics. The developments in nanotechnology are currently used to develop flexible displays, sophisticated conductors, precise electronic circuits and more
J. R. Minkel, Scientific American
There is still a long way to go until the thin nano-tube - a rolled carbon hexagonal mesh about a billionth of a meter thick - will bring about a revolution in the field of electronics. The tiny size, which makes nanomaterials so attractive as next-generation electronic components, is also the obstacle that makes them so difficult to process in large numbers. Researchers in the field therefore hope to commercialize the devices by utilizing existing manufacturing techniques. During the last year, we have also seen several examples that illustrate how nanoscale components can be integrated into the normal production processes, as well as the publication of a report outlining regulations for regulating work with nanomaterials.
In May 2005, Motorola's Physical Sciences Research Laboratory unveiled a prototype high-resolution television screen that instead of a cathode ray tube has a glass surface coated with a ziffany array of nanotubes. Nanotubes usually form in ordered arrays only at temperatures above 1,200 degrees Celsius, but James Jesky of Motorola and his colleagues managed to develop a metallic catalyst that lowered the threshold temperature to just a few hundred degrees.
Even the normal furnaces used to deposit thin silicon layers can reach these low temperatures. Other companies that have built screens based on nanotubes have scattered the tubes in a random arrangement within a paste-like substrate. But the resolution of these screens is lower, and their use requires a filter that complicates their production.
Nano-tubes are also at the center of the attempt to create displays printed from flexible polymeric components - electronics that have been called flexible electronics. Several research groups have mixed nanotubes with a flexible polymer to improve the material's electrical conductivity. A group from DuPont's research and development center reported in the summer of 2004 the first printing of such a polymer, on large surfaces, using existing technology. This technology, called thermal printing, uses a laser to melt the polymer and fuse it into a substrate, similar to the process of ironing. In 2005, the researchers reported on printing conducting, semiconducting and insulating polymers on the same surface.
A question that arises in the next step is how to turn the arrays of nanotubes into more complex devices in a convenient way. Bradley J. Nelson from the Swiss Federal Institute of Technology in Zurich manages to arrange hundreds and even thousands of multi-walled nanotubes on and between tiny electrodes. It does this by applying a normal two-dimensional electric field to a suspension of tubules. So he burns the top layers of the tube so they peel off, breaks the tubes in the middle, or twists them in other ways to create electrically controlled components: light emitters, rotating motion generators, and telescoping linear motion generators. Arrays of such devices can be used, among other things, as extremely resistant chemical detectors, or as self-focusing light emitters.
A more difficult problem is how to build precise electronic circuits from nanotubes or other nanowires. Chip manufacturers today simply burn the pattern they want on the chip. Researchers at the Hewlett-Packard Laboratories (HP) were among the first to propose building nano-circuits with the help of many nano-wires built in a two-and-a-half architecture (crossbar arrays). It is possible to create such a two-and-a-half system in a process of chemical self-assembly at low costs. Electrical activation of some intersection points between the nanowires will actually create the circuit. The same researchers were recently able to demonstrate in practice chips made of two-and-a-half systems of nanowires. They found that integrating more components into the system than necessary makes it possible to overcome the high defect rate of the tubes, and to still cram in a unit area a hundred times more devices than today's chips.
In recent years, policy makers have been very troubled by the question of whether to regulate the use of nanomaterials in regulations and how to do it. Nanoparticles penetrate living cells more easily than larger particles. In the summer of 2005, after a year's research, the Royal British Society and the Royal Academy of Engineering concluded that the nano-materials produced in large quantities should be classified in a new chemical classification in the existing regulations in the United Kingdom or the European Union, and recommended that toxicity studies be started immediately.
Nanotechnology connoisseur
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