Conductive Silicone Makes Flexible Circuits

Flexible circuits and wearables seem to be all the rage these days. We’ve got conductive paint, glue, and even thread. So how about conductive silicone? Well, as it turns out — it’s not that hard to make.

[Andrew Quitmeyer] has been researching flexible circuits for a while now, and recently stumbled upon an expired patent for flexible ignition cables, using carbon fibers mixed with a conductive silicone. He started playing around with it, and discovered that by dissolving pieces of carbon fiber in rubbing alcohol, letting it dry, and then mixing it into a 2-part silicone you get pretty good electrical conductivity. In fact, in the range of 40-150ohms, which is actually pretty darn impressive!

The following video will give you some ideas on exactly what you could make with flexible conductive silicone.

And a bit of background on his research into using platinum-cure silicone with the carbon fiber.

And if that’s not enough, have you ever tried making your own Sugru alternative? It’s called Oogoo.

45 thoughts on “Conductive Silicone Makes Flexible Circuits

        1. Is that conductive grey pubic hair? The first thing you pick up in the video. Also well done great to see these items conductive rubber is the future. I’m gonna start selling conductive rubber electrician’s screwdrivers I should make a killing.

    1. Hahhahahahaha you might think you are joking , but no, I totally work for Comingle.io the open source sex toy company and that’s exactly why I worked on making this. Google electric eel sex toy to see what I’m currently trying to recreate in rubber ! And yeah those are butt plugs in the shape of my thumb (or for the easily offended, no they are just thumbs)

    2. Bah, hackaday ppl are not interested in sex toys. Otherwise there would have been an article about dilduino, comingle…
      No, what REALLY interests HaD is: The Big Penises of US Army. Countless articles about cold war, nuclear weapons, and just… weapons. “DARN” weapons. And “FRICKIN” lasers. That´s it.

  1. Little wrinkled yellow robot warning! Instruct………..

    An extreme offensive one at that, but ready for electro-sex. Just an old headphone cord and plug it into your soundcard, download some e-sex synth patches and get it on.
    Seriously now this could be hacked into force sensitive control inputs, unless wear or something mucks it up. Two domes of rubber meeting under variable pressure.

      1. Personally I don’t like the instructables website, design wise. Splitting each thing onto twenty pages is very annoying and done mostly just to increase views on the ads that take up 40% of the page. Plus the full page pop-in-front that begs you to join is annoying. There are a lot of websites like that nowadays and it gets harder to put up with them.

          1. I hadn’t noticed that. Of course when I noticed the button and tried to click it it jumped out of the way because apparently they don’t know the size of the banner ad they are loading.

            I think my old man syndrome might be acting up.

          2. You *used* to need to be a member to “View All Steps”. That hasn’t been the case in a while now. Still have to click away the popup to join, but that’s not so bad.

  2. You cant dissolve carbon fiber in alcohol, you can disperse it but it has nothing to do with solvation… and this isn’t conductive it’s resistive. He needs carbon black, graphene or CNT if he wants a more conductive silicone he also needs to pass high voltage AC current during the cure in the direction he wants conductivity.
    And yes I have added these to platinum cure silicone and got a resistive material so the second video is not entirely correct.

    Other than that they already make conductive silicone, it has silver in it and can be as low as .05 ohms per cm.

    I do like his videography it’s all over the place, like me, so at least he has that.

  3. How can you actually claim that the silicone is conducting? Isn’t it obvious that the carbon fiber enclosed in it is doing all the conduction alone? BTW, I experimented myself with graphite powder (used locksmith graphite lubricant for keyholes) and the guy’s right: that’s definitely NOT working.

    1. “Isn’t it obvious that the carbon fiber enclosed in it is doing all the conduction alone? ”

      The point is to conduct current one way or another across what would otherwise be insulation. “Conductive silicone” describes the desired goal, not necessarily the physical makeup of the involved compounds. Fixating on semantics misses the forest for the trees, and imo reflects a failure to understand a “hack” in the context of a goal rather than as an abstract engineering challenge floating in a vacuum.

      1. So, the hunt is to find a way to conduct electricity thru silicone.
        And it is OK if the silicone is just the carrier for the conducting part.
        OK, I have a solution
        Ye Olde Piece of wire with silicon insulation…. Works fine. And is flexible as heck

        1. exactly, and mg previous comment was triggered by “dissolving carbon into alcohol” which is not just semantically wrong.
          Move on, no new material here, nothing to see…

    1. Yeah that stuff is great! and I use it to make hard-soft connections between silicone to PCBs for instance, but for somethings a mold-able conductive silicone is nice because you can have a large, 3-dimensional sensor (or actuator) in any size or shape you want, and with whatever surface. Plus the whole thing will be STRETCHIER than a metalwire simply covered with silicone. :)

  4. My (uneducated) guess as to why he is seeing better conductive properties when using just the carbon fiber nano tubes is similar to that of pickup sticks. When you drop them as a bundle they have a propensity to entangle when they hit their final form and thus create a great network of conductive paths.

    Adding carbon powder is like adding marbles to the mixture of pickup sticks. They cause the sticks to flow out more evenly and distribute across a larger surface, this spread causes fewer conductive paths from any one point to another point.

  5. “Hey Bevis, what if they used a taser with that thing.” “TP for bungholio!” joke aside.

    A thin layer on PVDF film would make for a good interface for movement to sensor data from an high response exosuit.

  6. I read about some companys patent filings.

    Apparently there is a trick to it. It’s called some thing like quantum tunneling effect, it’s used for heating elements like self regulating stuff.

    I need one badly but sadly too technologically inept and freaking poor to do it.

    It goes something like this, you need two standards of Carbon black,
    Type 1/ T1 – needs to be 5 times the diameter of Type-2/T2.

    T1 should have a relatively smooth surface, not like a ball but imagine like a roundish diamond see, so that the surface although having numerous edges doesn’t have any sharp peaks like a needle coming out.

    T2 should have spiky surface.

    From my pitiful googling, I’ve come to know that carbon black is sold on size of paryicle as N550 (commonly for tyre use) you will need this type for T2. But I couldn’t find anything about the surface characteristics.

    T1 would be like N990 I’m thinking.

    Basically it says the population of T1:T2 should be 1:5
    Average diameter of particles should be 5:1

    Now the trick is to apply oligomeric that is long chain silicone, which seems to be your methicone type lubricant to T2. Use T1 un adulterated.

    Now first we mix T1 in a silicone rubber, once well mixed we add T2 coated with the oligomeric lube to it and mix well.

    You need the particles in such numbers that the average distance between said particles is less than 100nm.
    This is so because the quantum channeling tunneling black magic doesn’t happen at distances more than that.
    Basically the spikey T2 will cause electron jumping from the T1 present in the bulk silicone non conductive matrix. Now due to the greater number of T2 particles multiple pathways are provided, something called galvanic isolation is detrimental and hence avoided in this manner and hence this arrangement is said to be Galvanic-“ally” connected I’m guessing.

    Now you take two copper sheets and place each on opposite side and connect each copper to a electric lead.

    We can use AC or DC current in this preparation.

    One more thing if read was thermal coefficient of expansion should be like above 50*10^-6 / °C , the application does say that this figure should be more than that both linearly and volumetrically.

    So when we pass current this thing will conduct electricity like a doped semiconductor I think, now was it n or p type I don’t know. It’s been years since I read any of that.

    Now it will sorta behave linearly or something regarding resistance, it will have PTC.

    When it reaches certain temperature depending upon the thickness, avg number of particles etc, the expansion will cause the inter particle distance to exceed the 100nm distance.

    This will stop channeling tunneling and the material will become abruptly an insulator. And it will be totally non conducting due to high dielectric strength.

    Also there was something about an electric field of 30V/mm or something which I couldn’t understand.

    This way a self regulating heater can be made which is very safe for use in bed warming pads.

    Btw the thivkness of the whole thing is like less than an mm I guess, I think I read it as 0.3 mm

    The inventor or first folks to patent this were a company called Conflux of Sweden.

    I need an electric warmer to give to someone as a gift but sadly they’re too horrid unrrliable in India. Plus I don’t want my mum dying of electrocution if she has a spill of water or fluids from old age conditions.

    But sadly these items sold by conflux is like way way expensive for use as bed warmer .

    Regards

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