Plastic conductor?

  1. plastic conductor???

    I just tooned in to the end of a segment on "daily planet" about this guy who found out a way to create a plastic conductor. He says it conducts electricity as well as a metal wire and is very light weight (and will literally change the world of electronics).

    Anyone have any more info on this or how it's done? I was doing something else while the TV was on in the background so I don't remember much of the details, but I remember the guy saying it was done through a chemical process.
     
  2. jcsd
  3. chemisttree

    chemisttree 3,723
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    Plastic conductors are usually called electrically conductive organic compounds. Polyacetylene is a well-known one. By weight, some of these conduct electricity as well as metal wire. By volume, the conductivity is usually less than most metal conductors.

    From Wiki:

    http://en.wikipedia.org/wiki/Conductive_polymer
     
  4. By weight?

    Previous poster stated comparisions of conductivity by weight. This is highly erroneous.

    Conductivity is controlled by a function of surface area and electon resistance. A 1-inch thick copper rod has far less conductivity than an equal mass of copper that has been spun into tiny threads. Electricity flows along the outside of materials...therefore the more surface area, the more capacity for electron movement (current or quantum vibration).

    A measure of electrical conductivity by weight is quite nonsensical. It's result would end in an equation of convoluted functions of surface area, geometrical topography, and volumetric ratios (which would all be needed to effectively remove mass from the equation...and thus solvable).

    Perhaps you were thinking of heat conducivity...but that would be a discussion about heat capacitance and transfer rates (for which materials could be compaired with regard to mass)...not in the realm of conductive plastics.
     
  5. berkeman

    Staff: Mentor

    You misunderstood chemisttree's statement. The point was that electrically conductive plastics are generally much less conductive than metal. The comment about "by weight" was meant to emphasize the characteristics of the material -- how they are optimized for conductivity (but still aren't as volumetrically efficient as metal).

    And your comment about electricity flowing on the outside of wires is only true for high frequencies, where the skin depth of the AC current shrinks to the order of the cross-sectional dimension of the conductor.
     
  6. When there is no current, but some charge, charge carriers certainly reside on the outer surface of a conductor because they are repelled from each other. Also, it is true that even when there is flow, the charge carriers on a superconductor still all move along the surface (but with a depth dependent on the max current density). That's why its perfectly fine to make a superconductor that is simply a coating of superconducting material on some non-superconducting substrate (as long as the maximum current density is not exceeded). However, for conductors that have even a slight resistance (copper at room temperature, etc.) when an external EMF is applied such that there will be flow, the carriers begin to take the paths of least resistance in order to carry the charge. That path includes paths within the conductor (not just on the surface). So the resistance of a copper wire is proportional to its length and its cross-sectional area. Additionally, multistrand wires do not exhibit any better conductivity than their solid counterpart. Multistrand wires are used mainly to allow more bending without damage.
     
    Last edited: Dec 3, 2007
  7. berkeman

    Staff: Mentor

    The poster may have been thinking of the use of Litz wire, which is a specialized kind of multi-stranded wire which does have a significantly lower inductance than solid wire:

    http://en.wikipedia.org/wiki/Litz_wire
     
  8. Well possibly. But then he should, of course, be alerted to the difference between inductance and resistance.
     
  9. Gokul43201

    Gokul43201 11,141
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    This post is riddled with errors, one of which has been pointed out by berke and fleem. In addition, dc conductivity is a material property and is intensive. It is not a function of surface area. Even the conductance, which is geometry dependent is not explicitly dependent on surface area for mesoscopic/macroscopic systems, but instead on the geometric aspect ratio. Additionally, the phrase "quantum vibration" has no business showing up in that sentence or anywhere in the post. To say that conductance is a function of electron resistance is silly, because it is trivially true but completely undescriptive, since it is defined as the inverse of the resistance.
     

  10. the man in the segment was the inventor of this conductive plastic, and said that, while he had patented it, he was still making deals with possible customers/buyers... so this is not a product that has yet seen commercial light by any means.

    he claimed that this was literally a plastic conductor (no wires, no metal, etc.)... he claimed that thanks to this technology, incredibly light and cheap electronics could be manufactured (i.e: without the need of metals: if memory serves me right, one of his prototypes was a remote control car that is made entirely out of various forms of this plastic: from the antenna to all its parts).

    I don't know much about electronics, so I hope someone who does saw the segment and might be able to explain it better. the show is usually reliable so I doubt it was a case of media misinterpreting science or something like that.
     
  11. Gokul43201

    Gokul43201 11,141
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    Was he a white-haired old man?
     
  12. berkeman

    Staff: Mentor

    Kind of hard to make an effective electric motor or solenoid without ferrous metals.
     
  13. he was rather young... maybe in his 40's, brown curly hair, somewhat chubby.

    like I said, I don't know the first thing about electronics, so my interpretation of this segment is probably very poor :biggrin:. but the segment did make a point constantly of how groundbreaking this new material was. that's why I was hoping someone here had seen the segment or heard about this material.
     
  14. Gokul43201

    Gokul43201 11,141
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    Conductive plastics (polyaniline, et al) have been around for a couple decades now, I think. I don't see what's new about this.

    Daily Planet does not air in the US! I tried to dig up old episodes from their CTV website, but the archives go back only to september.
     
  15. it doesn't? O I figured it did, seeing as some of the bigger canadian shows air in the US too.

    Yea, I tried looking for the episode in their website too but it doesn't go that far back. O well... I guess it'll remain a mystery.— either that or the predictions of the guy in the segment will turn true and revolutionize electronics and we'll all know what it's all about :biggrin:
     
  16. Gokul43201

    Gokul43201 11,141
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    Alan Heeger (one of 2 people that won the Nobel Prize for conductive plastics), in a talk he gave here a few years ago, promised us that the day when we will be printing circuit boards off an inkjet printer was just round the corner!
     
    Last edited: Dec 5, 2007
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