查看完整版本: Researchers make world's smallest piano wire

Researchers make world's smallest piano wire

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!D5Nf8v*t,O [color=DarkGreen]SEM image of a suspended nanotube. Credit: TU Delft[/color]HBe3zB
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[size=3][b]Researchers from Delft University of Technology and FOM Foundation(Netherlands) have successfully made and 'tuned' the world's smallestpiano wire. The wires are made of carbon nanotubes that measureapproximately 2 nanometers in diameter. The researchers have publishedan article on the subject this week in the scientific journal [/b][i]Nano Letters[/i][b].[/b][/size] V mX+^9}

'H9N kQ6Wq [size=3]The researchers at the Kavli Institute of Nanoscience Delft and the FOMFoundation made the small wires from carbon nanotubes, measuringapproximately [u]1 micrometer long and approximately 2[/u] nanometres indiameter. The tubes were attached to electrodes and initially placedabove a layer of silicon oxide. This layer of silicon oxide was thenpartially etched away with acid, which caused the tubes to detach andhang.
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A layer of silicon is contained beneath the silicon oxide. A strongand frequently variable alternating current is applied to this layer,which causes the hanging nanotubes to vibrate. The suspended tube isalternately attracted and repelled. The largest measured deviation forone tube was 8 nanometres. The distance of the nanotubes to the layerof silicon influences the electrical capacity to the layer of silicon.The movement of the nanowires is derived from these changes incapacity.
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\d],yNm;{ When the frequency of the applied current approaches the level ofthe suspended tube's eigenfrequency, it begins to vibrate morepowerfully. The order of magnitude of these frequencies amounts to afew tens of MHz. By varying the strength and frequency of the appliedcurrent, the research group led by Professor Herre van der Zantsucceeded in transposing the wire from a freely suspended state, to astate in which it is taut and vibrates. Van der Zant: "And as such itis like tightening a piano wire or guitar string. You can, as it were,tune the wire."G9t}7QSF
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The Delft researchers have developed a model that can satisfactorilypredict the vibrations of the nanotubes. The vibrating nanotubes arenot only interesting from a scientific standpoint; in future they canalso be used for other specific applications. Van der Zant identifiesone possibility as a hypersensitive mass sensor. "The nanotubes areextremely lightweight. If you suspend something from the tube that isalso extremely lightweight, like a virus, then the change in mass isrendered by a different vibration pattern. From this, you can determinethe size of the extra mass and deduce if it involves the virusconcerned." The vibrating tubes may also be of interest for GSM-relatedapplications (which now use resonators that vibrate in the GHz-field.)1F4@2|w2Q\1x9^d

(X7jMd\ Citation: [url=http://dx.doi.org/10.1021/nl062206p]http://dx.doi.org/10.1021/nl062206p[/url] E!u%G4j?Whr!_(T
Bending-Mode Vibration of a Suspended Nanotube Resonator - Benoit Witkamp, Menno Poot, and Herre S. J. van der Zant. [i]Nano Lett.[/i]; 2006; ASAP Web Release Date: 22-Nov-2006.
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[i]Source: TU Delft[/i]
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