Slashdot Mirror

← Back to Stories (view on slashdot.org)

How To Make Electronic Displays With Mood Ring Ink

Posted by timothy on from the cheap-tricks-are-the-best-kind dept.

Soychemist writes "Print some thermochromic ink onto a sheet of paper, put metal heating elements on the other side, and you have a rudimentary color-changing display. Chemists in the Whitesides Group at Harvard think that the devices could be used to provide a simple readout from cheap medical tests and kits that check water for pollutants. In the past year, the same scientists have made a three-cent medical test and improvised a centrifuge with an egg beater. Their aim is to invent useful gizmos with everyday materials."

33 comments

  1. The other what? by __aajfby9338 · · Score: 0, Offtopic

    Print some thermochromic ink onto a sheet of paper, put metal heating elements on the other, and you have a rudimentary color-changing display.

    Soychemist accidentally a noun.

    1. Re:The other what? by Anonymous Coward · · Score: 0

      Tagged as 'theotherside'

  2. Too bad it uses heat... by jpstanle · · Score: 1

    My first thought was "Oh neat, color electronic paper." Then I thought, "But if it needs to get hot (and stay hot for that matter), it would not be very useful for a portable device like an e-book reader."

    Perhaps with some chemical tweaking they could develop dyes that work at much lower temps?

    1. Re:Too bad it uses heat... by CarpetShark · · Score: 1

      Perhaps with some chemical tweaking they could develop dyes that work at much lower temps?

      Hmm. Doesn't human skin go pure white when you pass a current through it? ;)

    2. Re:Too bad it uses heat... by Anonymous Coward · · Score: 0

      Perhaps with some chemical tweaking they could develop dyes that work at much lower temps?

      If they did, wouldn't it be completely useless on a warm day?

    3. Re:Too bad it uses heat... by Vectronic · · Score: 1

      That's a security feature in case you leave it somewhere. The password is to wave it around like some reverse etch-a-sketch.

    4. Re:Too bad it uses heat... by Anonymous Coward · · Score: 0

      But then it could surely be used as a heat warning device for certain Apple products!

  3. Resistive ink by Rorschach1 · · Score: 3, Interesting

    I was thinking about making a thermochromic display for a custom watch, actually. Didn't know if anyone else had tried it before, but I guess I'm on the right track. It's going to take a lot of batteries to power, but I only really want it to run for Burning Man and Maker Faire.

    I'm going to see if I can screen print resistive ink onto a PCB to make the heating elements. Failing that, I'll just go with thin film SMT resistors. Anyone know if that has been done before?

    1. Re:Resistive ink by Anonymous Coward · · Score: 2, Informative

      I don't know if it's been done before, but SMT resistors will work quite well. Just make sure they're rated at the temperature the thermochromic ink needs to get to... if not, you could just solder some nichrome wire across the pads. You might want to consider heat sinking things so that it will be able to cool off quickly as well... a bit of a balancing act, that.

      Good luck making it cool in time to wear while the man burns!

    2. Re:Resistive ink by Anonymous Coward · · Score: 0

      Anti-Forgery

      Could resistive ink be useful in preventing check or dollar bill forgery? Have a handy bill tester that lights up a logo/emblem?

    3. Re:Resistive ink by Rorschach1 · · Score: 2, Informative

      Most of the films are rated for temperatures close to room temperature, though you can get other ranges. I've used through-hole resistors as heating elements before and they do indeed work quite well. A 1-watt metal film resistor will generate enough heat at 3 watts to melt its own solder joints. Long before that happens, it gets hot enough to melt through nylon or spectra, which is what I was using it for - a thermal knife for a load release.

      It's certainly not going to be done in time this year, but maybe next. What actually inspired me was upgrading my desktop CNC milling machine's spindle motor so that it can handle cutting brass easily. I cut a few test shapes and I love it - it machines easily and looks beautiful.

      I'm not really into steampunk, but I love some of the design elements. I'm working on a costume for next year that's sort of golden age of science fiction inspired, somewhere between Battlestar Galactica and a WWII German officer's uniform. I love the idea of a slightly bulky, machined brass wristwatch on a big leather band that's obviously electronic but clearly not a display technology in common real-world use, and I think it'll go well with the outfit.

    4. Re:Resistive ink by Anonymous Coward · · Score: 0

      If it's for Burning Man better make sure it's asshole proof.

  4. How is this electronic? by ale_ryu · · Score: 1

    Seriously, there's nothing electronic about this, it's only the mood ring ink connected to a resistance. I mean, it's all right for a home experiment but it's hardly useful.

    --
    Check out my blog!
    1. Re:How is this electronic? by __aajfby9338 · · Score: 2, Insightful

      Seriously, there's nothing electronic about this, it's only the mood ring ink connected to a resistance. I mean, it's all right for a home experiment but it's hardly useful.

      It's not electronic in much the same way that thermal printers aren't electronic.

    2. Re:How is this electronic? by Em+Emalb · · Score: 1

      I mean, it's all right for a home experiment but it's hardly useful.

      Bah, you kids and your fancy electric printers. This thing is useful, boy! Why, back before we had "thermochromatic" ink, we used our feces. And we hated it.
      So be glad of this advance, sonny. And make sure you shake hands with your right hand.

      (I kinda agree. Nifty experiment, pretty useless in practice)

      --
      Sent from your iPad.
    3. Re:How is this electronic? by Brett+Buck · · Score: 2, Funny

      Uh, it has to be "electronic" to be useful? Every hear of electric light? Or a toaster?

            Brett

    4. Re:How is this electronic? by Anonymous Coward · · Score: 0

      Uh, no, but it should be "electronic" to call it "electronic" in the headline...

    5. Re:How is this electronic? by triorph · · Score: 1

      Do you have some different definition of electronic to the rest of us? Doesn't matter it its simple or not, hooking up a resistance to a power supply is still electronic.

    6. Re:How is this electronic? by ale_ryu · · Score: 1

      That's just electric. From wikipedia:
      Electronics is a branch of science and technology that deals with the flow of electrons through nonmetallic conductors, mainly semiconductors such as silicon. It is distinct from electrical science and technology, which deal with the flow of electrons and other charge carriers through metal conductors such as copper. This distinction started around 1906 with the invention by Lee De Forest of the triode.
      So, there you have it.

      --
      Check out my blog!
  5. Obligatory PETA sub by Anonymous Coward · · Score: 0

    Cuttlefish and tooth picks - environmentally friendly

  6. gizmos eh? by Illender · · Score: 1

    what about making a electric toothbrush out of a dildo?

    --
    When I rule the world, I'll have squads of flame throwers fanned out around me, and for me, winter shall cease to exist
    1. Re:gizmos eh? by crtreece · · Score: 1

      BTDT

      --
      file: .signature not found
  7. Two questions by raktul · · Score: 2, Interesting

    What temperatures are needed to change the ink? Obviously if it needs to be really hot that is bad since it might burn the person holding it, while cooler temperatures can be affected by the atmosphere around the page causing problems. Would it make more sense to use a different material then paper to print the ink on to avoid accidental colour changes?

    1. Re:Two questions by megrims · · Score: 1

      Given that this is the substance used in mood rings--cosmetic devices which change colour according to minor variations in body temperature--I don't think burns will be an issue.

      The technology actually looks quite promising.

  8. Fun by Nom+du+Keyboard · · Score: 1

    Their aim is to invent useful gizmos with everyday materials.

    What a fun project to be a part of.

    Now how about finding something much more useful to do with those clunkers besides just crushing them into scrap? The current plan -- Democratically inspired, of course -- is one of the biggest wastes of already refined and manufactured resources imaginable, and an outright giveaway to the autoworker union.

    --
    "It's the height of ridiculousness to say for those 9 lines you get hundreds of millions."
    1. Re:Fun by Groggnrath · · Score: 1

      Right. Because that particular part of the stimulus has failed miserably.

      You know, there is a boat load of failed stuff you could be making fun of right now. Why troll something that actually seems to be working?

    2. Re:Fun by KillerBob · · Score: 1

      *theoretically* before a car gets crushed for scrap it's already stripped of everything useful. glass can be recycled, they'd be mad to not take out the catalytic converter (the platinum in a catalytic converter can fetch more money than the rest of the steel in the car is worth)...

      crushing for scrap is so that the parts can be melted down and recycled, which is a lot faster than digging the iron up out of the ground and smelting it into steel... unless you were thinking that the cylinder head from a 1962 Ford Fairlaine can be used on a 2009 model?

      --
      If you believe everything you read, you'd better not read. - Japanese proverb
    3. Re:Fun by mr_walrus · · Score: 1

      anyone crushing a 1962 ford fairlaine, or 1962 anything, otta
      have their nuts crushed.

  9. Not ink, PENCIL! by jeffb+(2.718) · · Score: 1

    (1) Put the thermochromic ink on one side of your (very thin) PCB.

    (2) Draw heating elements with a #2 (or, if you can find it, #1) pencil. You can get the resistance of a heavy graphite line pretty low; if that's not low enough, run traces along the long edges of each segment, instead of connecting to the ends.

    (3) Profit!

  10. The real article behind this by wrmrxxx · · Score: 3, Informative

    The summary links to Wired, which in turn links to the real article with the interesting details: http://www.rsc.org/delivery/_ArticleLinking/DisplayHTMLArticleforfree.cfm?JournalCode=LC&Year=2009&ManuscriptID=b905832j&Iss=Advance_Article

  11. like a patent.. by garun · · Score: 1

    it is simple to make it more complex..

    it has to be multilayered "sandwich":

    1 layer - insulator with horisontal conductive lines;
    2 layer - insulator mask;
    3 - filling mask with resistive compound;
    4 layer with vertical conductive lines;
    5 - on top of forth layer, printing pixels with thermochromic ink ;
    6 - protective coating layer.

    IC maybe will be like in LCD controllers but with higher currents ans slow refresh rate
    inks has to have high temperature of color changing - about 80 C - due to enviroment interaction