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Science Technology

Cambridge Team Spins Nanotube Yarn 70

FridayBob writes "They say it's bound to happen soon, although nobody knows exactly how and when. Well, perhaps the answer has arrived. It now seems as though some bright folks at the Cambridge-MIT Institute have figured out a way to continuously spin carbon nanotubes into a fiber. Will it be strong enough for a space elevator?" They're getting closer to commercialization (see older story) but not there yet...
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Cambridge Team Spins Nanotube Yarn

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  • by lfm_the_couch (663351) <lfm@the-UUUcouch.org minus threevowels> on Thursday July 08, 2004 @12:14PM (#9644155) Homepage
    ...then could we put out satellites with massive solar cells and harvest the electricity directly through the tether, rather than inventing "beamed power"? Probably not, if my dim understanding of electrical physics is any use...
    • by breadbot (147896) on Thursday July 08, 2004 @12:38PM (#9644437) Homepage
      Unfortunately, the cable is too long to send power through efficiently, since it has to reach up at least to geosynchronous orbit. Estimates of conductivity for a composite fiber are in the range of copper or other good metallic conductors. You'd get a heck of a lot of resistance through 25,000 miles of cable. Gotta beam it down or something.

      According to this calculator [allmeasures.com], 25,000 miles of copper with 1 cm^2 cross section (probably an over-estimate), would have a resistance of about 6700 Ohm.

      • by Orne (144925) on Thursday July 08, 2004 @01:24PM (#9645012) Homepage
        The longest land based transmission line [abb.com] is in the Congo at 1700 km, running at 500 KV DC. For the rest of us, that's 1,056 miles. So basically, we'd need 25x the longest transmission line ever built to date... so we could carry less energy than building one medium size fossil fuel plant on the ground.

        Now there are several tricks to power transmission. One, raise the voltage and lower the current, and you'll have less heating of the line, as temperature is proportional to current and resistance. Needless to say, this would incredibly complicate your anchoring system on earth. Next, current flows on the surface of a wire, so transmission lines are actually bundles of smaller "threads" wound together in parallel. This evenly distributes the energy, reducing the net resistance of the "wire".

        For a wire that long, you have to work with the old RCLG formulase for losses across the line... reactive charging losses and resistive heat losses. The line would be so long that the voltage would decay long before you'd reach the other end, and no power could be transferred.
        • Next, current flows on the surface of a wire.

          Are you sure about that? Can you back that up with references that don't refer to:

          - Superconductors (which exhibit this behavior)
          - A/C skinning effect (which still doesn't flow on the surface of the wire)

          As far as I knew, electric current flows through the wire, and electrons collide with one another and spin from atom to atom to reach the positive end. If current flows outside the wire in both regular wires and superconducting wires, where does the resista
          • Current is distributed evenly in a transversal seccion of a conductor only when its DC. When the current is alternating, there is an effect called the skin effect in which the current distribution tends to go to the outer rim of the transversal section. As frequency increases, more dramatical is this effect. So if it is DC you are right, there is no skin effect, and might i add there is no way ur getting AC power from solar cells.(so even the RLCG model of the line is questionable as L tends to 0 and G to
          • My mistake... I work with EHV AC power all day, forgot that DC is slightly different. And no, I wouldn't recommend AC over that distance either.

            One thing that just popped into my head is, how would you deal with a grounded "wire" who's other end is in the clouds during a thunderstorm? Lightning is the electrical static discharge of the temperature front as it moves across the landscape, when the charge stored exceeds the permittivity of air. If you had a wire passing through the storm front, wouldn't it
            • Considering it is the most desireable do to it's low resistance, would it not also transmit the current long before it hit the very high levels seen in a lightning bolt (except maybee at the leading edge of a fast moving storm).
              I'm currious as to what all this would mean. I would think the lower levels being transfered might reduce any potential damage. But would you also have a large area around the line that was lightning free? Would this create issues as the ground level would be higher than at the
      • Estimates of conductivity for a composite fiber are in the range of copper or other good metallic conductors. You'd get a heck of a lot of resistance through 25,000 miles of cable. Gotta beam it down or something.

        I've been considering this for awhile, and I think the best solution is to convert the energy to fuel. Specifically, anti-matter. If we can develop an effective way to extract energy from matter/antimatter annihilation, then we could use Solar Energy to power antimatter fuel plants. The antim
        • I've been considering this for awhile, and I think the best solution is to convert the energy to fuel. Specifically, anti-matter. If we can develop an effective way to extract energy from matter/antimatter annihilation, then we could use Solar Energy to power antimatter fuel plants.

          And if we had some ham, we could have ham and eggs - if we had some eggs.

          Antimatter might be a very dense way of storing energy, but making it is incredibly inefficient [psu.edu] (PDF). The efficiency of current particle accelerators

          • We don't want to be part of your missle defense system. What makes you think we'll let you use our vast forests to fuel your energy-hungry economy.

            Keep your light out of our country! ;)
    • by another_henry (570767) <slashdotNO@SPAMhenryhallam.cjb.net> on Thursday July 08, 2004 @12:48PM (#9644552) Homepage
      Actually, the beamed power is not tricky at all. It is easy to do using microwaves, which can be produced efficiently with magnetrons (evidence is in your microwave oven) and converted back into electricity using rectennas.

      A rectenna is basically an array of tiny antennas and diodes which rectify the microwaves back to DC. They have been around since the '60s and can operate at up to 80% efficiency (record is 84% efficiency for 30kW of power).

      In 1964 William C. Brown succeeded in demonstrating a microwave-powered helicopter! (Sorry, I was unable to find any pictures). You can find more interesting info on this google search [google.com].

      • Yah, but beaming microwaves in significant power ranges would be lethal or at least significantly toxic to humans near the beam path.

        This would be okay for unmanned loads such as resupply, but obviously a bad idea for manned transport.

        I don't want to stand within sight of the transmitter either, without standing in a nicely sealed thick metal room with lots of faraday cage layers outside as well for redundancy. I've seen what microwaves can do to meat (last night at dinner).
        • Stay out of the tightly-focused beam, and you'll be fine. If you don't actually catch enough to cook you there and then, it can't hurt you - radar operators used to commonly stand in front of the dishes on cold days to warm up. It's only resistive heating.
        • Microwaves are pretty easy to stop, so you only need a single collector dish, and you could be right above or bellow said dish (depending weither the power was comming from earth or space) and not have to worry about being cooked.
      • Pictures and more info about the helicopter are at http://www.mtt.org/awards/WCB's%20distinguished%20 career.htm [mtt.org]
      • Isn't the rectenna that giant satellite dish that came out of Cartman's butt in the first episode of SouthPark? Just asking.
  • Chain Mail (Score:5, Interesting)

    by justanyone (308934) on Thursday July 08, 2004 @12:32PM (#9644365) Homepage Journal

    Can no one see the fault in this scenario?

    If you want a super-strong (tensile strength) fabric, you don't make it by crochet or other weaving methods. You make chain mail with it.

    The crucial facts (IMHO) are these:
    • Nanotubes have very high tensile strength (100 GPa?)
    • They have very low surface friction
    • they are difficult to make in long lengths
    • Snags are inevitable in any real-world situation
    The key here is that making a fabric like chain mail, by having nanotubes that are of a specified uniform length like 1/2 cm, formed into a continuous loop (torroid or donut shape), and interlocking these loops in a redundant chain-mail fashion (no pun intended), will lead to exceedingly strong fabric.

    However, making a weave, with a long, continuous string, will lead to a fabric that can collapse by the cutting of the string at any point along it's course - this will lead to fraying and the fabric will pull apart.

    Solid state physisists, please enlighten us if I'm way off base here, but it certainly seems the better way to go for high-strength tethers and fabrics.

    Humbly but convincedly,

    --Kevin J. Rice
    • Re:Chain Mail (Score:3, Informative)

      by breadbot (147896)
      Very interesting. The goal of a space elevator tether is longitudinal strength, which means that the links would be stretched along one axis. I wonder if the folds and pinches at the top and bottom would cause any problems, and if you'd have to make a chain link out of a large number of nanotubes to prevent pinching. And what about rubbing?

      You mention cutting an individual fiber and thereby causing the whole fabric to unravel. For a space elevator, the prevaling thinking is to make a composite materia

    • Re:Chain Mail (Score:5, Interesting)

      by jgardn (539054) <jgardn@alumni.washington.edu> on Thursday July 08, 2004 @12:49PM (#9644563) Homepage Journal
      It can't happen like that. You are talking about a level of organization that only crystals exhibit.

      Exactly how do you propose to make toroidal nanotubes? Exactly how are you going to interlock them into a pattern? This is the difficult part, and if you figure that out, I see a Nobel prize in your future.

      Right now, the current thought in nanotube technology is that you aren't going to make a single, continuous tube. Even if you could, the maximum length is not going to be practically infinite.

      Instead, what needs to happen is that you must "spin a thread", like we spin thread today. You take fibers and organize them so that they are randomly interlocking.

      The difficult part is getting the nanotubes to stick together with a strength equal to the strength of the nanotubes. This is no problem with cotton, polyester, or sheep's wool, because each individual fiber is hairy and they stick together like velcro. The strength of the connection can be stronger than the strength of the individual fibers.

      It is known that nanotubes are "sticky" to each other. There is a mutual attraction caused by various forces. This laboratory used that to their advantage by continuously spinning thread at the rate of several cm per second (!). However, the thread isn't sticking very well to each other or the stickiness isn't strong enough. The end result are threads that aren't much better than sewing threads.

      Perhaps they can add a step where they put the nanotubes into a bath of chemicals and stretch the nanotubes or compress them to cause them to stick more strongly together. Perhaps if those threads are weaved together, the weave itself will cause the nanotubes to stick together better. Perhaps a thread can be developed that when put under tension compresses and thus increases the friction. These are all possible scenarios, and are the next steps.

      Or perhaps this is just a really good way to make and store millions of nanotubes a second, to be dissolved and organized later.

      Or maybe you can take these nanotubes and assemble them with some kind of process to line them up end to end. Maybe they will weld themselves chemically if they are lined up and brought near to each other's ends.

      More experimentation is needed. Wouldn't you like to be in that lab at this time, playing with these threads?
      • Re:Chain Mail (Score:3, Interesting)

        by justanyone (308934)
        Yes, okay, it's hard to make.

        But perhaps not impossible. What I'm proposing is to have the end in mind when designing the machinery.

        IDEA: Perhaps fabricating nanotubes with a deliberate molecular flaw that allows attachment of another hydrophilic molecule, say, "HPM A". Then have a hydrophobic molecule B ("HPM B") similarly. Arrange for HPM-A and HPM-B to fold at a specific set of temperatures and have HPM-B disengage at that point.

        In otherwords, build a molecular assembly device that manufactures a
        • Technologicaly speaking, you are daydreaming. It is unbelievably difficult to make even microscopic amount of differentialy end-functionalized nanotubes. You would need tonns of that stuff for the elevator.

          I was thinking something rather different. It is known that single-wall carbon nanotubes in fluffy state (some preparation of nanotubes look like black cotton) will self-ignite on air when iradiated by fash from a camera.

          (This has been discovered 2-3 years ago by accident, by a grad student making pictu
      • "It can't happen like that. You are talking about a level of organization that only crystals exhibit."

        And biological systems. In theory one might be able to engineer a nano-machine or bacteria to do the grunt work. But as someone else has pointed out the bend isn't a good idea anyway.

        • You are correct. Biological systems would be the only other route that would make sense for this kind of structure.
          • To bad someone who sounds credible pointed out the structure itself doesn't make such good sense.
            As a fan of fantasy the concept of high-tech chainmail like this is kinda fun to think about. Not that the links would be very visible if at all.

    • Re:Chain Mail (Score:5, Informative)

      by Goldsmith (561202) on Thursday July 08, 2004 @10:41PM (#9649491)
      As a solid state physicist, working with nanotubes, who is also a member of the SCA, I found your post quite interesting.

      The first problem is that nanotubes don't grow into toroids. They can form spirals that look like toroids under any but the most powerfull microscopes, but these spirals will unravel very quickly. That point is a weak rebuttal, because we could probably close those rings with an electron or ion beam if we really wanted to.

      Also, keep in mind that there are very, very few molecules which are "stiff" all by themselves. Carbon nanotubes are definitely not one of them. It would be like making chainmail out of very strong cooked noodles. Really what you want is more than the 4 links provided by chainmail. By tangling these up, we can link up to many times more other nanotubes than by controllable copying of a two dimensional nearest-neighbor lattice. For example, if we have a three dimensional cubic lattice of interlocking rings, we have 6 links in a nearest neighbor (chainmail) case, and 14 in a nearest and next-nearest neighbor case, increasing redundancy and bonding energy. We could keep going by weaving these things together. In a really tight weave (or a huge tangle like what these nanotube fibers really are), you may have one fiber connected to hundreds of others.

      Except for one more issue, all the weaving done right now might still theoretically be made stronger by closing the ends of the nantubes to avoid unravelling (so your general idea is good). If stress is put on a bend in a nanotube, it will lead to a "5-7" defect where two hexagonal rings become one ring of 5, and one of 7, inducing a 15 degree permanant bend in the tube. These defects lead to nanotubes which have at best 50% the tensile strength of a non-defective tube, but often more like 15%. That's why so much work is being put into aligned nanotube fibers. These fibers have been measured to be stronger than any other known material. If these aligned fibers are then woven, they are lighter and stronger than Kevlar. Coincidentally, the molecularly woven (tangled) nanotube fibers made by these guys at MIT are not much stronger than generic clothing fiber. The key is to weave the fibers macroscopically and allow the nanotubes to bend less than 15 degrees on a molecular scale.

      Hope this was helpful.
    • by ckaminski (82854)
      Which is why they invented ripstop. YOu know, that stuff sailboats use to keep their sails from getting destroyed when a seagull crashes through 'em?
  • by justanyone (308934) on Thursday July 08, 2004 @12:46PM (#9644535) Homepage Journal
    Larry Niven postulated in a Ringworld or other Known Space writing the existence of what he called 'Sinclair Molecule Chain'.

    This substance was a single molecule that was very, very small in diameter, but had a very, very high tensile strength. This was formed into a string and was used in ropes and other stuff for various purposes. It was also useful for cutting things, since the chain was so strong, and the application of force across such a narrow point, that it would cut through most substances easily.

    I have some questions:
    • Has anyone tested this theory with this molecular chain stuff?
    • Would it make a good knife?
    • How vulverable is it to shocks (is it elastic or brittle)?
    • Can I make a better lawnmower blade out of this stuff, much like a super-strong weedwhacker wire?
    • Would chain mail (see other post) made out of it be bulletproof?
    • Would it be a good instead of steel in concrete as rebar (since the main bad-thing about reinforced concrete is corrosion of the rebar)?
    • Would making carbon-fiber composite structures be better with nanotubes, or would it even cut through the glue substrate?

    Just some basic questions... Maybe someone from the MIT team that created this stuff can answer them.

    --Kevin J. Rice
  • In theory, Professor Windle explained, a satellite could be "tied" to Earth with a cable, but it has to be light and very strong, hence the excitement around carbon nanotubes.

    Can we tie our natural satellite too??

    We can then have mooneering in the lines of mountaineering. Way to climb to the new heights.

    • Yes, but the end of the fiber would trail across the Earth as the Earth turned. The moon takes 30 days to go around the earth, the day takes (ah-Hah!) 1 day to go around, thus the cable would be traveling about 1000 miles an hour, would heat up and fail, which would just wreck the climbing scenario.

      Unless!! You could run 1000 mph to jump on, climb VERY FAST to get above the atmosphere before it failed, and carry enough oxy water and food to climb the 286,000 miles up to the moon. Okay, there'd be no grav
      • The only solution is to use a series of atomic explosions for a Hohmann transfer to put the moon in geosynchrous orbit! Which would produce a giantantic Moon always visible in the southern horizon of America! Which is now underwater due to tidal forces! Surf's up, Earthlings!
        • You forget that the Moon also rotates, so it would wind the tether around itself.
          • The moon doesn't rotate with respect to the Earth, which is the significant point. The same face always points to Earth.
            • Wouldn't that mean it doesn't actually rotate at all? Doesn't it merely revolve around the Earth?
              • Actually, the Moon rotates at the same rate that it revolves around the Earth. That is why we always see the same side. Try it yourself. Start facing one direction and walk around something in a circle, while always facing the same direction. You will note that the side that is facing the center of your "orbit" changes. Now try walking around again, always facing the center. After making one complete "orbit" you will note that you have also made one complete turn.

                Anyway, if the Moon were to be relocated to
                • Right, we're gonna have to build some huge-ass, um, blast-panel-things embedded in the Moon perpendicular to the surface, on opposite sides of the Moon. We can then use more useful atomic explosions to change the Moon's rotation to be whatever we want it to be. I suggest making the axis of rotation perpendicular to the surface of the Earth, hanging a space elevator off the nearer lunar pole which, while spinning, should maintain the same position with respect to the earth. Whether the elevator should spi
                • Thanks for the suggestion, it really helped give me a deep insight into the concept. Just one question though.
                  How do I unwind all this fiber from around my waist without getting so dizzy I puke, or taking so long I can rest by playing Duke Nukem Forever?

  • by Glog (303500) on Thursday July 08, 2004 @01:40PM (#9645216)
    Nanotube Knitting 101
  • They say it's bound to happen soon, although nobody knows exactly how and when. Well, perhaps the answer has arrived.

    Am I the only one who is puzzled about what this actually means? Perhaps the editors should actually be editors and eliminate unnecessary sentences in stories that don't make sense.
  • The result is an extremely fine and strange black thread that is about as strong as clothes fibre, and can carry an electrical current.

    The last thing one would wear over the already conducting human bodies is cloth made of another conductor.

    OK! My opinion would change if this fibre can store some bits and bytes also though

    • Re:Conductor (Score:1, Interesting)

      by Anonymous Coward
      If you wear a cloth conductor, the path of least resistance becomes your clothes, not your body. In some cases not a bad thing.
      • Unless my feet are not on this big conductor called the earth or the cloth is in connection to some other good conductor, the electricity *is* bound to turn me dead

        • What electricity? It conducts electricity, it doesn't generate it...you would have to bring your conductive clothes into contact with an already dangerous exposed source, which clothes made of insulating fibers would be no guarantee of protection from. And even then, the danger is almost entirely due to electricity passing through the core of the body, which it is unlikely to do when said core is surrounded by a far better conductor.

          Really, your complaints remind me of a comment I once heard while I was wo
    • by Anonymous Coward
      "The last thing one would wear over the already conducting human bodies is cloth made of another conductor."

      Actually, a conductive high-tensile strength cloth would make an ideal ballistic jacket that also counters tasers (since the current from the taser would travel through the jacket rather than the person). Connect to ground and you have the ultimate anti-static device for techs.

      "OK! My opinion would change if this fibre can store some bits and bytes also though."

      Err, YOU might like the idea of weari
  • I can't wait to see this ad:

    New carbon nanotube dress shirts. Light, breathable, stain resistant, and bullet proof. On sale now in all men's sizes. 2 for $80

  • by EigenHombre (684799) on Thursday July 08, 2004 @04:38PM (#9647309) Homepage Journal
    I noticed noone here has commented on the toxicity [nih.gov] of carbon nanotubes. From the NIH website:

    "These results show that, for the test conditions described here and on an equal-weight basis, if carbon nanotubes reach the lungs, they are much more toxic than carbon black and can be more toxic than quartz, which is considered a serious occupational health hazard in chronic inhalation exposures."

    Not sure I'd wear a shirt or even chain mail made of these things....

  • a Space Bridge.

We all agree on the necessity of compromise. We just can't agree on when it's necessary to compromise. -- Larry Wall