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Toys

Magnetic Fluids 103

Polo writes: "Remember those magnetic sculpture things you can buy at the mall where these small metal pieces stay in one shape. Imagine doing that with Ferrofluids. This is just too cool. Dan is the nerd's nerd." Well, can't get any higher praise that that, I suppose. :) I have a couple of neodymium magnets and yes, they are much fun. Never played with magnetic fluid though.
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Magnetic Fluids

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  • SIGGRAPH (Score:5, Informative)

    by LS ( 57954 ) on Friday October 19, 2001 @06:28PM (#2453458) Homepage

    Japanese artists Sachiko Kodama and Minako Takeno did an art piece displayed at SIGGRAPH using ferrofluids. Memepool [memepool.com] had some links about this back in august.

    LS
    • Damn, you pointed it out first.

      But yes, this was at SIGGRAPH, called ``Protrude, Flow''. They had to put signs up so that people wouldn't try to touch it. They also had funky lighting so that it looked *really* otherworldly.

      Definitely the most surreal thing at the show. It ties ``Meeting Jim Blinn'' for my coolest SIGGRAPH moment.

      Note: LA sucks. Be glad it's in San Antonio next year...

      -grendel drago
  • by sfbanutt ( 116292 ) on Friday October 19, 2001 @06:31PM (#2453465) Homepage
    Ferrofluids have been used in magnetic clutches. You have two plates facing each other with vanes on them. Put them in a ferrofluid tank. When the magnetic field is absent, either shaft will spin freely without effecting the other. Add a magnetic field and WHAM, the shafts are locked together. I seem to remember there being a problem getting a decent amount of shear strength though. There was an article on this in Scientific American a few years back in the Amateur Scientist column.

    • Magenetic clutches...

      Yes. The paper feed mechanisms in the big line printers of the mainframe era often used ferrofluid magnetic clutches and brakes. Because they can clutch and release far faster than mechanical clutches, they're used when precision control of intermittent motion is required. Ferrofluid clutches can take constant, repeated impact loads with almost no wear; the energy is dissipated in the fluid, rather than in surface friction. Very neat.

      That technology goes back to at least the early 1960s.

  • by cribcage ( 205308 ) on Friday October 19, 2001 @06:31PM (#2453467) Homepage Journal
    The "nerd's nerd" couldn't handle three measly hits? This has to be a "slashdotting" record. ;-)

    crib
  • Ferrofluid links (Score:5, Informative)

    by Black Acid ( 219707 ) on Friday October 19, 2001 @06:34PM (#2453473)
    Ferrofluids are indeed cool but DansData is not the only place which has information on them. They can be used to create nanostructures [msu.edu] and defy gravity for environmental engineering [lbl.gov]. In case you're wondering what exactly ferrofluids are, here's a good excerpt from the previous link:
    Ferrofluids are colloidal suspensions of nanoscale magnetic particles in a carrier fluid; the particles form magnetic domains separated by coats of dispersant only a molecule thick. These magnetic fluids have been used in many ways--to form airtight seals around rapidly moving parts, to move drugs in the bloodstream and rocket propellants in spacecraft, even to cool and dampen powerful audio speakers. Now steerable ferrofluids may give rise to new tools for subsurface environmental engineering and laboratory safety.

    At Berkeley, they use magnetic fluids to control movement of underground fluids without any contact. Interesting stuff. For an introduction to ferrofluids, see University of Wisconsin [wisc.edu]'s excellent article.

  • Ferrofluids (Score:4, Informative)

    by smunt ( 458722 ) on Friday October 19, 2001 @06:35PM (#2453474) Journal
    check this [wisc.edu] link. It's the first link on the page (which is unreachable by now).
  • aHA! (Score:4, Funny)

    by Soko ( 17987 ) on Friday October 19, 2001 @06:35PM (#2453476) Homepage


    I have a couple of neodymium magnets and yes, they are much fun. Never played with magnetic fluid though.


    That explains the form errors trying to reply to this story.

    Umm, Michael? Could you keep your fscking magnets away from the fscking servers? Thanks.

    Soko
  • Some other links: (Score:4, Informative)

    by morcheeba ( 260908 ) on Friday October 19, 2001 @06:42PM (#2453481) Journal
    Check out this cool picture [sciencefriday.com] from Science Friday [sciencefriday.com].

    And a meatspace link: check out ferrofluids for yourself at the exploratorium [exploratorium.edu] -- if the exhibit is still there (it was maybe 4 years ago, upstairs), they have a tank of ferrofluid (with I think a lighter different-colored fluid floating on top). Pressing the buttons activates different electromagnets under the fluid, and it forms bumps on the surface (maybe protruding through the different colored liquid, as in the picture above, if I remember right). It's neat to see the surface of a liquid that is not flat, yet not moving. The exploratorium is well worth the visit if you're in the SF bay area.
    • I don't recall it. Unfourtunately Exploratorium seems to be loosing its cool factor.
    • I was at the Exploratorium in August of this year, and they did have a ferrofluid table upstairs (on the far side of the entrance).

      A (micro?)computer was attached to the display, and you could switch on various magnets to make different patterns, have them turn on and off at a few frequencies, etc. Very very cool!
  • we were thinking of buying very fine iron spheres (goodfellow [goodfellow.com] has some) and making this stuff. But we ran into problems with the numbers for the magnetic field strengths.

    Anyone know how many turns of a coil runnig at 1Amp you'd need to make a 1cm by 1cm crosssection of this sort of stuff remain rigid against a newton of shear?

  • I got the article in time. The pics not.

    find it here [initfour.nl]
  • by Mike McTernan ( 260224 ) on Friday October 19, 2001 @06:53PM (#2453501) Homepage

    Never played with magnetic fluid though.

    Michael can't have been to a science museum of late. I can remeber seeing small tanks of magnetic fluid that allow you to wave magnets around near them to see what happes in museums a couple of years ago.

    Oh, and Wired magazine had a lovely picture of magnetic fluid in a beautiful state that was to be shown at Siggraph (See wired [wired.com] for article check here for video [siggraph.org])

    • " . . . small tanks of magnetic fluid that allow you to wave magnets around near them to see what happens in museums a couple of years ago"



      Wow! Magnetic fluids that affect museums in the past? There must be some kind of temporal anomoly going on here!

  • by FFFish ( 7567 ) on Friday October 19, 2001 @06:56PM (#2453505) Homepage
    Lee Valley Tools [leevalley.com], besides being a generally cool place with some delightful woodworking tools, has spherical magnets.

    And, no, to presuppose the silly question I was asked earlier, of course one of the poles isn't in the centre of the magnet. If it were, how the hell would the flux lines get to the outside?!

    These would be the equivalent of a bar magnet lathed spherical, allowing them to roll around and do other neat shit.

    FWIW, Lee Valley also has awesome rare-earth disc magnets. I've got a handful of them. They can suck through a good 2" of wood. Damn near impossible to get off the fridge door. Does nasty shit to any nearby wallets, too. And don't even think about letting them near your monitor.
    • And, no, to presuppose the silly question I was asked earlier, of course one of the poles isn't in the centre of the magnet. If it were, how the hell would the flux lines get to the outside?!

      If it were shaped like an apple and you wanted both poles inside there would of course be no problem. But to have one pole in the centre of a sphere you'd need to use a worm hole.

      Irony and a pun. I couldn't resist.

      -- MarkusQ

    • And, no, to presuppose the silly question I was asked earlier, of course one of the poles isn't in the centre of the magnet. If it were, how the hell would the flux lines get to the outside?!

      DUH!

    • One other warning, don't put them on opposite sides of a finger. While it won't necessarily squeeze your finger off, the problem comes if and when they slip and lock together with some of your skin between them.

      -Paul Komarek
  • just wait until this hits the infomercials.. they'll probably have some sort of offer for "therapeutic gel" that you bathe in. just toss your favorite electrical appliance in, and voila!
  • not that cool really (Score:2, Informative)

    by Anonymous Coward
    Actually I used to use the stuff for educational purposes and it is gross ass hell. Gets on everything and wont wash off. Fun for the first 30 seconds.
  • Mirror for the video (Score:4, Informative)

    by Skaven04 ( 449705 ) on Friday October 19, 2001 @07:09PM (#2453521) Homepage
    I got the video downloaded just in time...

    here [lunarpower.org]

  • fairly good mirror (Score:3, Informative)

    by Anonymous Coward on Friday October 19, 2001 @07:13PM (#2453524)
    http://homepage.mac.com/crayz/magnets/magnets.htm [mac.com]

    Thank Apple for the bandwidth
  • That fella has some seriously fucked up links.
    Look for the one where he talks about using magnets as body mods...follow it and see what the twins are doing.

    How about amputation and reattachment, parts swapping between the two?
    Photoshop, I hope, but I dunno.
    • That interview was posted April 1, 1999. I assume it was photoshopped.
    • http://www.bme.freeq.com/people/addsub/index.html
    • For the record, the twins page was an April Fool's Day Joke done by Shannon from BME. However, so many people believed it that he had to put up a page saying it was fake! The photo on that page is Shannon's backyard too.
      All fake people, no one is swapping limbs for the hell of it just yet. However, cutting [freeq.com] parts [freeq.com] off [freeq.com] happens quite a bit.
      • We had a big debate at my office on whether that was real or not (before I read this post :). Most of us believed it, simply because we've all seen guys (and girls) with very messed up things done to their bodies. Implants, mostly. And of course, there's the weirdos who amputate themselves.

        So if people amputate arms and legs and fingers on themselves, I don't think there's any reason why this wouldn't really happen some day. I think it would be kinda cool to have an extra limb hanging out of my stomach :)

        And of course, that "alien finger" would just kick some serious ass! (I know a dude who had one of his fingers taken out all the way to the wrist - it almost looks normal, except you have to do a double take because he only has three fingers :)
  • Well this week we've had revolutionary discoveries with new magnetic solids, and now magnetic liquids. Does this mean that they'll discover a magnetic gas next? It would certainly help in those awkward situations where you just can't hold your fart anymore.
  • The Ferrofluids site is down.....already

    The /. magnetic influence apparently caused an influx of charges to decimate the site.

  • saw a presentation on magnetic fluids a few years ago at school... tons of applications because the viscosity can change with the magnetic field applied, so basically lots of active damping. I've seen applications such as bike suspensions to gun recoil to washing machines.

    another cool trick is to put the stuff in a suringe that is connected to a second suringe, fluid will move back and forth with the plunger until a magnet is place near by then it gets
  • by SlamMan ( 221834 )
    We had this when I was little. We called it mercury. Only this time, it won't make us like a the mad hatter.

  • Ah... We killed him already! Get a mirror up quick!
  • Anyone tried getting someone to drink some of this liquid and trying to catch them with a large magnet ;). On the serious side, Dan's data appears to have ben slashdotted.
    • Anyone tried getting someone to drink some of this liquid and trying to catch them with a large magnet ;).

      Better: send them to the airport.

      -- MarkusQ

      P.S. That begs the question--what comes after strip & cavity search?

      And do we realy want to know?

  • by FrenZon ( 65408 )
    It shows how far science has come - we've finally found a replacement for that sticky (cornflour and water) goo kids play with, which solidifies under pressure - now they don't even have to move their arms! laziness abounds!
  • Magnetic Fluids (Score:4, Interesting)

    by Anonymous Coward on Friday October 19, 2001 @08:52PM (#2453593)
    Fluids influenced by magnets have been around for a while.

    One of the problems facing the space program in its earliest days was how to re-fire liquid fueled rockets in a weightless environment. If you think about it, just exactly how do you get the fluids in a tank half full of rocket fuel to take a position over and in the sump of the tank so the pumps can supply reliable measures of fuel and oxidizer to the engines combustion chamber.

    The innovative solution was to mix the fuel and oxidizer with a ferrous based additive so that a large magnet at the sump of the tank would draw the fuel and oxidizer to the sump. This isn't a magnetic fluid but it is one of the ingenious solutions to a myriad of engineering challenges facing our space program.
    • One of the problems facing the space program in its earliest days was how to re-fire liquid fueled rockets in a weightless environment. If you think about it, just exactly how do you get the fluids in a tank half full of rocket fuel to take a position over and in the sump of the tank so the pumps can supply reliable measures of fuel and oxidizer to the engines combustion chamber. The innovative solution was to mix the fuel and oxidizer with a ferrous based additive so that a large magnet at the sump of the tank would draw the fuel and oxidizer to the sump. This isn't a magnetic fluid but it is one of the ingenious solutions to a myriad of engineering challenges facing our space program.

      I'm not familiar with this, do you have a source for this?

      The solution that NASA typically used to solve this problem was to fire the maneuvering thrusters briefly which would impart an acceleration onto the fuel and force it to the proper part of the fuel tank.

      Seems a much cheaper and simpler solution, no?

      Rich...

  • by napa1m ( 154836 ) on Friday October 19, 2001 @08:59PM (#2453608) Homepage
    A few friends and I bought a large bottle of the stuff, it's pretty neat to play with along with some magnets, but you need some SERIOUS power to get any real decent results, initially we were messing around with some discarded large speaker magnets and voice coils (fixed magnetic power). We went so far as to have ordered some higher power electromagnets and some extra hardware to control their strength. Unfortunately due to the recent events in our neighborhood (NYC) we haven't had a chance to experiment much more lately.

    Oh and its more like liquid than goo, so dont get your hopes of creating a giant black goo monster up too high.

    Anyway, if you want to pick some up for yourself try these places:

    Edmund Scientific [edmundscientific.com]
    (also has magnets, electromagnets)

    Teacher Source [teachersource.com]
    (this is where we got our large 1000ml bottle)

    and more listed at the official ferroftec web site:
    ferrofluidics [ferrofluidics.com]

    -nA
    • Crack open one of those 100 Mb hard drives (which any geek worth his salt must have lying around), and pull out the rare earth magnets. Those things whoop speaker magnets any day of the week! (They're actually kind of worrisome to handle.)


      -Fantastic Lad

  • i want one!! i've only been able to access a couple sites, considering everything's been slashdotted :P but this looks fun !!



    friend walks in.. "so.. what did you do today?"

    me: ..well.. i went to school, took care of my son.. and played with Ferrofluids !@#$#@


    friend calmy (but nervously) walks away..
  • this stuff's been in science education supply houses for some time. it's very cool, and you can approximate it with very ancient drained engine oil - iron block of course - and of course if your jalopy yeilds much of this stuff, you're going to have another challenge on your hands soon enough, an old junkyard with otherwise shot engines are a good source.

    remember, used engine oil is not very pleasant stuff...

    to visualize field lines, larger iron particles in mineral oil in a clear plastic vial is cool too.

    edmunds, fisher sci, carolina have these.
  • get ferrofluid here (Score:3, Informative)

    by AnotherBrian ( 319405 ) on Friday October 19, 2001 @10:07PM (#2453748) Homepage
    Small Parts [smallparts.com] has an experement kit with 50cc bottle and some megnents to play with. Look at at the left bar and go down, it's under "DEMO KITS". I ordered one a while ago, it's pretty neet. ($50.00)
  • by johndr ( 109432 ) on Friday October 19, 2001 @10:43PM (#2453819)
    This has been around >15 years. In fact some of the tools that made the chips in your PC probably had ferrofluidic bearings. Because these liquids can be held in place by magnets, you can make a feedthrough into a vaccum chamber that can be rotated. The fluids have low vapor pressure so you can have a high vacuum system with a rotating shaft entering it - that's very difficult normally. The fluid seals between the shaft and the sleeve, where the air would normally leak in. Good down to about 10^-10 of an atmosphere. Try www.ferrofluidics.com [ferrofluidics.com].

    Regards, John the semiconductor capital equipment designer.
    • Their Feedthrough Catalog promises only 10^-9 mbar (I suppose you meant 10^-10 mbar, not 10^-10 bar). Anyway, do you really have a clean (hydrocarbon-free) mass spectrum after baking a chamber using these feedthroughs ? What about stray magnetic fields ? I know, I could ask the manufacturer but I'd like to hear the opinion of a user.
  • by Velex ( 120469 )

    I wonder if you could come up with a non-toxic ferrofluid, sneak it in someone's drink, then pull them around with a big huge magnet? Or even better... he's sure got an attractive personality

    /me ducks
  • It reminds me of that "water" on the islands of Riven that would avoid heat. It would travel up the sides of glass, and even suspend itself in air if given sufficient heat to avoid. Neat stuff!
  • interesting site about magnetism, FOund Here [jnaudin.free.fr]
  • It cant form complex objects, but it can form basic weapons, sharp objects and stabbing weapons.

    The Terminator
  • So when do we get to see them build the first Liquid Terminator out of this stuff?

    I realize the first metal Terminator has yet to be done, but after Sony realizes that AIBO isn't very useful, I think we'll start seeing some really fun stuff walking out of their labs.

    The whole Liquid Metal Morphing Killer Robot thing though, man... that's where it's at!

    I can't wait until I have a barrels full of minions to call upon for my evil deeds!
  • I recall reading about magnetorheological fluids about 4-5 years ago in one of those "homebrew VR" books. They wanted to try using them as force-feedback devices (e.g. fluid under the fingers in a glove which hardens to suggest a solid surface). Basically iron filings in oil, as I can remember. They also talked about electrorheological fluids (sp?)- basically cornstarch suspended in vegetable oil- a little easier to control than MR fluid in that you didn't need cumbersome electromagnets, just a small step-up circuit needed for the roughly 25 Kvolts to get the lattice to "lock" (i.e. to get the ER fluid to harden). (Despite what you're thinking, it wasn't dangerous if everything was tight and well-insulated). They quoted a company's price for commercial ER fluid- something like $200/quart- when the homebrewer could do just as well with cornstarch/oil. I'd think you'd need to put an emulsifier in there if you were to hold the cornstarch particles in suspension for any extended period of time. Now I want to find that darn book... believe it was "Garage Virtual Reality" by Linda Jacobson. Might've been the other half-dozen "homebrew VR" books I bought around that time, though. :-)

  • Ferrofluid is fun stuff, and has all kinds of uses as others have outlined...including mechanical parts, seals, and rocket fuel.
    My employer [immunicon.com] also uses ferrofluids for cell separations for diagnostic purposes.
    Currently, we're developing an early stage cancer diagnostic system with the ferrofluid-based technology.

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