The computer friendly virus

The last thing most people want in their computer's memory is a virus. But now a team of scientists has used a virus to make a memory device, according to research in this month's Nature Nanotechnology.


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The computer friendly virus (AOP; N&V)
DOI: 10.1038/nnano.2006.55

The last thing most people want in their computer's memory is a virus. But now a team of scientists has used a virus to make a memory device, according to research in this month's Nature Nanotechnology.

The memory device developed by Yang Yang and colleagues is based on the tobacco mosaic virus, which is best known for infecting the leaves of tobacco plants. The team coated the virus with a layer of platinum nanoparticles, embedded this in a polymer, and then sandwiched the resulting nanostructure between two electrodes. When a voltage was applied, the device displayed an 'on' state that remained stable until the voltage fell below a certain value, resulting in an 'off' state.

Although the switching speed is slow compared with established devices, and the switching action is still not fully understood, it should be possible to improve the performance through further research.

Author contact:
Yang Yang (University of California, Los Angeles, CA, US)
Tel: +1 310 825 4052; E-mail: [email protected]

Here come the nanoSQUIDs (AOP; N&V)
DOI: 10.1038/nnano.2006.54

For many the word squid conjures up images of multi-legged sea creatures. But a SQUID is also an effective device for measuring magnetic fields. The smaller the SQUID the more sensitive it will be and in this month's Nature Nanotechnology scientists report the first nanoSQUID.

A SQUID - or superconducting quantum interference device - consists of a loop of metal that is cooled to close to absolute zero so that electrical current can flow through it without meeting any resistance. For such a loop to work as a SQUID it also needs to contain two 'junctions' that act as obstacles to this supercurrent. The nanoSQUID built by Wolfgang Wernsdorfer and colleagues is unique in using carbon nanotubes to form these obstacles.

These hollow tubes of carbon atoms - which have diameters of one billionth of a metre - are about ten times narrower than the smallest junctions used in previous SQUIDs. In addition to measuring magnetic fields the nanoSQUIDs could also be used to explore many fundamental phenomena in quantum physics.

Author contact:
Wolfgang Wernsdorfer (Laboratoire Louis Neel, Grenoble, France)
Tel: +33 476 88 7909; E-mail: [email protected]

Soap sorts out nanotubes (AOP; N&V)
DOI: 10.1038/nnano.2006.52

A soap-based approach could solve a long running problem for producers of carbon nanotubes according to research in Nature Nanotechnology this month. On account of their excellent electronic and mechanical properties, carbon nanotubes have been one of the hottest topics in research for 15 years. However, applications have been held back by a major problem - making nanotubes always produces a mixture of metallic and semiconducting nanotubes. Various methods for separating these two types of have been demonstrated, but they all have complications.

Mark Hersam and co-workers wrap the nanotubes in their sample with a mixture of surfactants - or soap - and then spin it around in a high-speed centrifuge for between 9 and 24 hours. The centrifuge spins at 64,000 revolutions per minute, generating forces that are some 170,000 times stronger than the force of gravity. The end result is that metallic and semiconducting nanotubes, which have different densities, can be separated. It is also possible to sort nanotubes according to their diameter.

Although just micrograms can be sorted at present, the use of an industrial centrifuge could enable grams of nanotubes to be sorted in less than a day.

Author contact:
Mark Hersam (Northwestern University Evanston, IL, US)
Tel: +1 847 491 2696; E-mail: [email protected]

Also in this issue...

Torsional electromechanical quantum oscillations in carbon nanotubes
DOI: 10.1038/ nnano.2006.57

Giant piezoresistance effect in silicon nanowires
DOI: 10.1038/ nnano.2006.53

A nanoplasmonic molecular ruler for nuclease activity and DNA footprinting
DOI: 10.1038/ nnano.2006.51

Linker-free directed assembly of high-performance integrated devices based on nanotubes and nanowires
DOI: 10.1038/ nnano.2006.46

Nature Publishing Group announces the launch of Nature Nanotechnology

Nature Publishing Group (NPG) is delighted to announce the launch of Nature Nanotechnology, a new research journal dedicated to all aspects of nanoscience and nanotechnology.

The journal's editors, who are based in London and Tokyo, are all PhD-level scientists, and their diverse scientific backgrounds in different areas of physics, chemistry and biomedical engineering reflect the multidisciplinary nature of nanotechnology. The Chief Editor, Dr Peter Rodgers, joined NPG from Institute of Physics Publishing, where he was Editor of Physics World.

The first issue of Nature Nanotechnology, published today and available online at, reflects the journal's broad scope by including topics as diverse as the separation of metallic and semiconducting carbon nanotubes to potential memory devices made from tobacco mosaic virus.


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Published: 04 Oct 2006

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