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Science Technology

Sketchable, Stretchable Circuits (acs.org) 34

JMarshall writes: A new, elastic silver ink allows stretchy circuits to be drawn using a regular pen. Unlike previous inks, which have been made with silver nanoparticles and are prone to clog pens over time, this ink begins as a silver salt mixed with adhesive rubber (abstract). After writing, the ink is brushed with a formaldehyde and sodium hydroxide solution that reduces the silver ions to conductive silver nanoparticles. Researchers strung 14 LED lights together using the ink. The lights stayed lit even through stretching and bending the rubber sheet the circuit was drawn on.

Sketchable, Stretchable Circuits

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  • by Anonymous Coward

    Doesn't your standard graphite pencil do this?

    • Graphite is less conductive than silver.

      If you're looking to "draw" a resistor, then graphite might be a good choice.

        In Apollo 13, I believe, one uses a pencil and a pice of paper and fills the surface of the paper with graphite and then rolls it, giving it to his partner and says: "this, I believe, is a resistor". It was needed for some equipment that has failed before.

  • Why do they keep experimenting with silver? Isn't it too expensive to ever be viable in commercial manufacturing?

    • by creimer ( 824291 )
      Silver is a consumable commodity. By some estimates, nearly half the silver ever mined since ancient times is gone. When silver supplies start running low, prices will go up substantially. But not anytime soon.
      • Silver is an element. If you recycle your electronics it can be recovered. when it becomes scarce enough to care we'll just melt down our trash and get the precious metals out of it.

    • It's difficult to make an ink that comes close to the conductivity of copper used in pcbs. It's even more difficult to make it stretch. Silver is a great conductor. We use gold because it doesn't corrode, but it sounds like silver has some desired properties that would be difficult to reproduce with another metal.

    • Re:Why? (Score:4, Interesting)

      by solidraven ( 1633185 ) on Tuesday December 22, 2015 @06:46PM (#51167943)
      Screen printed silver is the main conductor for cheap printed electronics... Two barely trained operators with a small machine can run a batch of a few hundred thousand pieces within a week with screen/stencil printing equipment. So a bucket of silver paste, some plastic sheets, and a moderately clean space will do. In the meanwhile copper might look cheaper at first glance, but you need to consider the processing cost as well. When considering a single sided circuit with the same volume you'll need at least a few you need hundred square meters of photoresist, large quantities of obnoxious chemicals (degrease, developer, etchant, stripper, plating solutions or OSP), way more space for the lines (degrease, roll laminate photoresist, illuminate, remove protective foil, develop, etch, strip, OSP immersion/spray or plating), not to mention the cost of the water treatment plant assuming you're not running it in China where you can just dump it into the river I suppose. For assembly the circuit boards still have an advantage: solder paste is a lot more forgiving than conductive adhesives. Needless to say, PCBs are well on their way out for certain applications! Obviously copper still has a few major advantages, it's a great heatsink, mechanically more forgiving, able to carry great currents easily, and is very easy to assemble components on. But think about medium volume RFID, keyboards, signs, etc. and you'll usually end up with screen printed silver paste as most economical solution for medium to lower-end high volume manufacturing. For extremely high volumes you could consider aluminium as conductor in more than a few cases, but lets not get into those pesky details!
  • Anonuyms covert http://www.haberelazig.com/ [haberelazig.com]
