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Science

The Amazing Bend-o-Nanotubes 12

Posted by Hemos
from the key-technology dept.
Auxon writes "Dr.Dobb's reported today a new discovery in the nature of carbon nanotubes that may be a key contribution to the realization of nanotechnological dreams. The article describes the accidental findings by "Hongjie Dai, Stanford assistant professor of chemistry, and graduate student Thomas Tobler in collaboration with University of Kentucky theoretical physicists," who used an Atomic Force Microscope (AFM) to bend a tiny nanotube. As the tube bends, the electrical conductivity decreases; something predicted NOT to happen in previous theoretical work. "As one side of the tube is pushed closer to the other, carbon atoms form bonds across the inside of the tube. Normally, each carbon atom binds to three other carbons, leaving one electron free for use in conducting electricity. But when the walls of the tube come close together, each carbon binds to four rather than three carbons. The resulting decrease in the number of free electrons causes the electrical conductance to slow. "The AFM tip squashes the tube, causing each atom to bond with more atoms," said Dai. "This causes the tube to turn from an electrical conductor into an insulating structure similar to that found in diamonds." Remarkably, the dent disappears once the perturbing tip is removed. This high mechanical reversibility allows the full recovery of the nanotube's electrical property, Dai said.""
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The Amazing Bend-o-Nanotubes

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  • by Ka0s64 (200106)
    This technology had been predicted to be used to make coiled structures (i.e. solenoids) on a nano scale allowing nano-mag fields. Unfortunately now that this has been proven wrong, they'll have to use it more as a damper. I think it would have been more useful the way it was predicted.
  • forced labor!!!

    I mean, uh, graduate students.

    Yeah, that's what I meant to say....

    (-;

  • Hey, if you've never done a microscopy experiment, quickly go and enroll in an intermediate lab course in physics. It's one of the most incredible experiments we did last year as an undergrad doing atomic force microscopy as well as scanning tunneling microscopy.
    Sad part of the story being that our professor sort of broke a tip (oops!). Minor detail? Eh....
  • I'll agree with you there. Atomic Force Microscopy is amazing. The physics and operation of an Scanning Electron Microscope is very interesting. It's similar to a huge television tube.

    If you are interested in a field/career that uses a lot of microscopy, I recommend Materials Science Engineering. This field is a great application of modern physics to the area of design and engineering. A typical MSE graduate will have experience with an AFM, SEM, TEM, or an STM.
  • The neat thing about the nanotube is that they form spontaneously when carbon is heated. If you burn a candle, chances are you're creating carbon nanotubes in the chaff from the candle. The only problem is, it's not many of them, and they have to be separated.

    The big boys just use more carbon and a big spark, causing millions of nanotubes to randomly form and fly about all over the place, where they can be used to cause lung disease and serve as a choking hazard for graduate students until collected and sorted.

    Hopefully someday something good will come of all this great research...

  • Most designs in nanotechnology I've seen (most notably a lot of Eric Drexler's structures) are built out of carbon atoms. It my understanding of this is right, then structures made of carbon atoms have the potential to bond under preasure, and they'd definately be under pressure in mechanical systems.
    I'm still a nano-fan though -- because nan* is cool =)
  • The designs you mention are based heavily on the mechanical properties of carbon fullerene cages, not their electrical ones. Also the ability of carbon to bond is the basic property on which all this science is based.

    There are a number of projects that are looking at the electrical properties of carbon nanotubes, such as doping them with large electron rich atoms in the hope of producing superconductors and being able to produce nano scale wires for microprocessor like devices. After reading this article it seems that the team were trying to lay out a carbon nano tube in the hope of conduncting electricity. They then found that When they bent the tube it stopped conducting, something that was not predicted. This result will cause people to chanage the way they think about carbon nano-tubes. Simply bending then into place will not work so we will need new structures to form bends in the tubes, if they are to conduct.

    The bonding you are so worried about is only temporary, the structure of a nano-tube is very stable (which is why it is a surprise that this happens) to move from a nano-tube to diamond (which is the next stage of bonding for carbon) would take insane ammounts of energy. These are strong, robust structures that are still very usefull.

    There is great potential here for even more advances in nano-tech, this research has shown that nano-scale mechanical relays are possible!

    (yeah ok so smaller more transistor like systems have already been thought of...)

  • A burning candle will not produce nanotubes of any great length, yes probability suggests that some will be formed but they will be insignificant to all the other compounds released from the wick.

    As for the big-boy method, sure that is what they do but it is usually in an controled and _enclosed_ environment. Yes the product is nasty and can be carcinogenic but generally they are not allowed to "fly about all over the place" if you are doing it differently i'd start asking for danger money :)

    Ahh what joys Prof. Kroto has bestowed upon the world!
  • Maybe he's using the Venus Equilateral method: leave the experiment in the open and put the experimenter in a tin can.

    (Venus Equilateral is a fictional space station from the 1950's. When a vacuum was needed for experiments -- such as creating new vacuum tubes -- they could use a lab which was open to space and work wearing spacesuits.)

  • by SEWilco (27983)
    Please stand by. This article vanished from the main page, so there will not be many more replies.

    When it gets bent back to the proper shape, resistance to the travel of electrons toward this article will be reduced and posting may continue. Except we've aged off the main page and are less visible.

  • Hey do you have a book or author reference for that?

    I love old sci-fi stuff.

    hmmm, collecting all those nanotubes in orbit would be interesting :)
  • Jeff, the coolest thing about nanotubes is their potential as a lightweight alternative to solid metal storage of hydrogen.
    As you know, vehicles with hydrogen propulsion systems need to carry fuel, and simple pressure bottles are essentially unsafe at any speed - even if the walls are thick enough to withstand collisions, failures of the valve assembly could be catastrophic.
    Safer methods have until recently centered around metallic storage, jamming the hydrogen atoms into palladium and/or various metal hydrides. Most of the research on this, incidentally, is being done by Germans.
    Unfortunately, Nelly Rodriguez of Northeastern University is said to have patented the concept of nanotube hydrogen storage, so don't hold your breath waiting for it to reach your driveway any time soon.
    These guys [aps.org] are trying to figure out exactly how/where the hydrogen is absorbed.
    --Charlie

We have a equal opportunity Calculus class -- it's fully integrated.

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