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    • CommentAuthorKosmopolit
    • CommentTimeJun 29th 2010 edited
     (8478.1)


    This is pretty damn cool.

    Memory metals have been around for a while now there's memory plastic.

    A team led by Robert Wood of Harvard University and Daniela Rus and Erik Demaine at the Massachusetts Institute of Technology made a square sheet of glass fibre 4 centimetres wide and patterned with 32 triangular tiles. The seams between triangles are made from flexible silicon rubber and a "shape memory" alloy foil.

    Each foil was given a memory by folding it in two and holding it in a vice as it is heated to 420 °C for 30 minutes. When unfolded and then allowed to cool, the foils retained a memory of the fold. They would re-adopt the shape when heated above a "transition" temperature of 70 °C.

    The researchers used origami simulator software to work out the sequence of folds required to create two simple structures – a paper aeroplane and a boat. They then sent a current through the foils, heating them above their transition temperature and so causing them to fold again. By controlling precisely when a current was applied to each foil, they ensured that the flat sheet folded into its pre-designed shape inside 20 seconds (see video).

    Although the team has so far managed to create only simple origami shapes, they say the technique could make tailor-made objects if the size of the triangles is reduced and their number increased. "Imagine foregoing all the tools in your toolbox and instead using a stack of self-folding sheets to produce the tools and structures you need for a particular job," says Wood.
    •  
      CommentAuthorbjacques
    • CommentTimeJun 29th 2010
     (8478.2)
    Dammit. These articles always leave out the most important details, like how can I get some and how much does it cost?
  1.  (8478.3)
    Excellent.
    •  
      CommentAuthorSara 013
    • CommentTimeJun 29th 2010
     (8478.4)
    "The sheet itself is made up of rigid tiles and elastomer joints and is studded with thin foil actuators (motorized switches) and flexible electronics. The demonstration material contains twenty-five total actuators, divided into five groupings. A shape is produced by triggering the proper actuator groups in sequence. And this is accomplished via a series of stickers that contain the circuitry that prompts the actuators to make the folds, which are then held in placed by magnetic closures."

    While really novel, not exactly a "memory plastic" akin to "memory alloys".
    Foil, actuators, and circuitry is sort of cheating. ;)

    I wish they'd hurry up with perfecting the fabrication of SM/SE alloys into thin sheets and even foils.... So far, I've only found one company that even comes close, and the limitations are disappointing. [/nerd]
  2.  (8478.5)
    Interesting. Most plastics we use have a 'memory'. If you slowly heat a 2 liter jug it will start shrinking back into the little test-tube it was originally formed from.
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      CommentAuthorJohn Skylar
    • CommentTimeJun 29th 2010 edited
     (8478.6)
    I don't understand why it needs all the electronics if it has to be heated to yield memory, or why it has to be heated if it has all the electronics.

    One should obviate the other, no? It seems like the two articles contradict each other.

    Edit: Eh I just read the paper to answer my own question. It seems that they used heat-set memory to make each folding joint "remember" that it wants to be folded, but the actuators and electronics serve to heat individual joints. So theoretically, if you heated the whole sheet to 70C, it would just crumple, but if you use the electronics to heat specific joints, you can get preprogrammed shapes without having to do any of this heat-treating stuff.

    So, the 420C step is part of the initial fabrication process and the end-user can make "any" shape they want without having to heat the plastic beyond 100C. The New Scientist journalist apparently failed to explain the distinction. I'ma go back to my lab bench now and stop sciencing all over this thread.