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How To Cut a Nanotube? Lots Of Compression
An anonymous reader writes "A pipefitter knows how to make an exact cut on a metal rod. But it's far harder to imagine getting a precise cut on a carbon nanotube, with a diameter 1/50,000th the thickness of a human hair. In a paper published this month in the British journal Proceedings of the Royal Society A, researchers at Brown University and in Korea document for the first time how single-walled carbon nanotubes are cut, a finding that could lead to producing more precise, higher-quality nanotubes. Such manufacturing improvements likely would make the nanotubes more attractive for use in automotive, biomedicine, electronics, energy, optics and many other fields."
Here's the Brown/KIST researchers' video, a rendered simulation showing the buckling action http://www.youtube.com/watch?v=PzNqW_d0QGc&fmt=18
This is a mildly related movie of actual electron microscopy of a flat graphene sheet finding its most stable configuration after a hole was punched in it http://www.youtube.com/watch?v=EogdalfXF4c&feature=related&fmt=18
The broken nanotube under high pressure has the advantage of having lots of other carbon atoms in a similar predicament close enough nearby that the tube's wall can reform, while the flat sheet simply falls apart due to its own tension and lattice vibrations.
Nanotubes punch holes in cells like molecular needles which is why there's a lot of interest in making antimicrobial surfaces out of them.
Sigs are too short to say anything truly profound so read the above post instead.
Carbon nanotubes (CNTs) and irradiation happen to be the general subject of a term project I'm finishing up...
There's a lot of uses for CNTs ( http://www.sciencemag.org/content/297/5582/787.full Might work. Might be paywalled. Yay University). The article didn't look to specific. (Or just plain wrong) I'm not clear if they're cutting a single CNT at a time or not.
One approach I've seen is suspending CNTs in a H2O2 solution, and irradiating with gamma rays to get shorter more uniform lengths of CNTs. The result basically is sphaghetti. A potential application though is as an additive in epoxies for strength. Identify the ideal length for structural purposes, and irradiate CNTs to get said length. This article also mentioned using ultrasonic treatment or whatever to shorten CNTs. (So this article is not new science, I think) ("Shortening of multi-walled carbon nanotubes by c-irradiation in the presence of hydrogen peroxide," Jung, et al., 2008)
I've also seen electron irradiation for cutting multi-walled nanotubes. The electron microscope pics look almost like chopped up tree trunks.
Diameter of (single walled) CNTs is on the order of 0.5 to 5 nm. (Interestingly, carbon fiber fibers have diameters on the scale of microns, e.g. 1000x greater)
Hire a teeny tiny samurai.
#DeleteChrome
They have been show to behave in a manor similar to asbestos when inserted into mouse tissue http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2783215. However, when trying to determine the dangers of using a given material in a product there are two factors that need to be considered. One is how large of an expose is dangerous. Water will kill you if you drink enough of it. The second other is mechanisms of exposure. If you smashed the glass in your window and ate it would shred your stomach lining and probably kill you. Does this mean that we should ban the use of glass?
The reason asbestos was so bad is they put it in insulation, which when disturbed released a lot asbestos into the air. From there it could be inhaled. You can design a product using carbon nanotubes in such a way the the risk of exposure minimized. This would include steps such as embedding the carbon nanotubes in a polymer in a fashion such that significant quantities of carbon nanotubes will not be released into the air and coating the surface of the product with a material to will prevent significant quantiles from being absorbed though the skin while in contact.
There are two reasons that carbon nanotubes have not shown up in commercial products. The first is price. If I am recalling correctly carbon nanotubes cost about 100 dollars per gram. For comparison the price of gold in about 30 dollars per gram. The second is that actually carbon nanotube composites have so far had properties far worse than classic composites models would predict. Two reason for this are that carbon nanotubes are hard to evenly disperses within the filler material and the bonding between the filler material and the carbon nanotubes has been more problematic than it has with larger diameter fibers such as carbon fiber. That being said carbon nanotubes still have the potential to be a hugely useful material for many possible applications; however, there are still many basic research questions about producing and using carbon nanotubes that need to be resolved.
Imagine a hair's diameter is 50 km then the diameter of a nanotube is 1 meter. This gives you a pretty good idea how the dimensions compare ;)