• PicŪ Basic


  • High Performance Conductive Silicone

    Basic Recipe:
    (Contributed to the Public Domain 2015)
    1.Mix Chopped Carbon Fiber (under 6mm lengths) with a bit of rubbing alcohol (to break it up)
    2.Let mostly dry
    3.Whip together the Carbon Fibers with the Part A of the silicone
    4.Add Part B, and mold it!

    High Performance Conductive Silicone
    Example part A part B silicone supplier




    Here is the full article - taken from Instructables




    RUBBERY CONDUCTIVE FUN! Build Waterproof, Wearable, Bouncy, Heatproof, Low-Resistance, Transparent, Indestructible circuits!
    Plus it's real easy to do, and requires few exotic materials!
    The goal here is to open up an amazing material, Silicone, that is becoming more and more accessible to the DIY community to the wonderful possibilities of electronics. DIY Conductive materials (conductive thread, paint, glue, fabric) have let craftspeople incorporate electronics in their project in uncountable fun ways. In the way that soft circuits let makers explore digital technology while utilizing the amazing properties of textiles, I think silicone circuits (silc circuits) have the potential to open another arena of physical-digital crafting in sculpture, wearables, prosthetics, toymaking, and special effects.
    For those who want to get right to it, here's the basic recipe, and I'll go into lots more details about this in the later steps (including materials, suggestions, and project ideas). It's pretty simple, you just need the right materials, and the right process. With this method you can utilize many of the properties of high performance silicone, and create shapes and designs both thick and thin.
    Basic Recipe
    (Contributed to the Public Domain 2015)
    1. Mix Chopped Carbon Fiber (under 6mm lengths) with a bit of rubbing alcohol (to break it up)
    2. Let mostly dry
    3. Whip together the Carbon Fibers with the Part A of the silicone
    4. Add Part B, and mold it!
    Example Projects Described
    • Rubber Breadboards
    • Anemone Touch Sensors
    • Rubber Finger Mold Styluses
    • Conductive Rubber Film
    • Cap-Touch Quiz Games
    • And MORE!
    What's awesome about Silicone?
    Silicone is an incredible (but sometimes frustrating material) with many amazing properties that highly compliment many problems with the way people usually do electronics with metal:
    • Waterproof: Your circuits can be inherently weatherproofed. Leave them in the jungle! Bring them into the ocean!
    • Durable: Can stand up to large impacts! Make toys for pets to toss and smash!
    • Flexible: Can be worn on the body, stretched, played with.
    • Translucent: Which lets you add colorings that respond to heat, light, or electricity to change colors or glow!
    • Body-Safe: Silicone is pretty inert and non-toxic. It's like rubbery glass. There's a reason they use it for food trays and sex toys. Also no horrid fumes when you mix it! You can mix it in your weird basement!
    • Mold-Able: Unlimited shapes and sizes and textures. That's why the best movie props and halloween masks are made from it
    • Grippy: You can stab things into it (like wires!) and they will stick, and be held in place!
    • Insulative: Stops electrical shorts (unless of course you make it conductive!)
    Previous Works
    This is not a new idea, but it's one that has been generally only possible in big industrial processes. It has been quite difficult to figure out a formula that works for the DIY enthusiast who also doesn't want to work with my gross, potentially toxic chemicals. Folks have been trying to figure out how to make conductive silicone yourself in the DIY community for a long time with some success. The amazing instructables user mikey77, for instance, has the standard instructable for conductive rubber.
    Most DIY techniques, however rely on incorporating graphite powder into the silicone which has many drawbacks. Examples of such drawbacks to these methods include: making the rubber brittle (falls apart, not rubbery), messy (leaves black stuff on you), high impedance (500kohms++), and being limited to tin cure silicones (e.g. GE silicone 1 which is not as easy to make thick objects, not as stretchy and not food and body safe). The tin cure silicones also prevent platinum cure silicones from curing, so you cannot incorporate this into bigger silicone projects. I have spent 2 years working with the fantastic open-source sex toy company Comingle (www.comingle.io), looking through many papers and projects with some limited details about various different techniques for doing this, but when implementing them, they have all come up short in do-ability or performance.
    I owe many thanks to the incredible engineer Craig Durkin, for helping me with this project!
    This new type of carbon fiber silicone (which sounds cool) solves a lot of these problems!
    Advantages of Carbon Fiber Conductive Silicone
    I ran across the idea of using carbon fibers in an old (thankfully) expired patent https://patents.google.com/patent/US3680027A/en?q=... They add 5% carbon fibers to a mix to increase the conductivity of already conductive silicone, but it works great just on its own!
    This style of making your own conductive silicone has lots of advantages compared to other techniques I have seen including:
    • Rubbery AND Conductive: Others tend to get brittle and not stretchy when made conductive
    • Non-Toxic: Just silicone and graphite! The MSDS's of these are quite low on toxicity! No gross metals or solvents!
    • Low Resistance: 40-150 Ohms compared to 100's of kilo ohms of other techniques. This means you can use it for capacitive sensing, electrical traces, and maybe even EEG sensing!
    • Quick: You can mix and have ready to use parts in half an hour! No waiting weeks for your molds to de-gass
    • Clean: Most graphite mixes leave gross crud, and leaves black smears on stuff. This one is nice and clean!
    • Electrically Stable: Needs more testing, but it seems that slight changes in pressure or bending do not greatly change the resistance of the material.
    • Tight-Connections: Making Hard-Soft interfaces from things like metal wires to soft conductive fabrics is always tricky, but this rubber offers a way to firm up connections both physically and electrically!
    • Fully Mold-able: Doesn't pour quite as easy as regular silicone, but, since you can use platinum cure (additive-cure) silicone, this conductive rubber can be molded into any shape, thick or thin! And it can be combined into any other silicone projects you are working with!


    Theory















    Conductive Silicone totally already exists at the industrial level (e.g www.stockwell.com) but finding a way for the average person to make and mold their very own conductive silicone has been elusive. Instructables user Mikey77 has shared the standard solution for a long time now with his conductive oogoo. But it has several drawbacks: brittle, long cure times, high resistance, leaves black smears (at least when I make it).
    Core Concept
    The basic idea of conductive silicone is that, while silicone itself is super insulative, you can impregnate it with conductive particles. Often this is done with small metal or carbon particles (this has a decent breakdown http://link.springer.com/article/10.1007/s00779-01... ). For instance people mix in copper or silver particles. Graphite (like in conductive ink and glue) often in the form of Carbon powder or Carbon Black is probably the most common because it is cheap, non-toxic, and doesn't corrode.

    Common Problems / Difficulties
    Silicone is a fickle material though. Adding different substances can lead to many different problems. Some common ones encountered in this pursuit are:
    • Cure Inhibition: The stuff added prevents the silicone from curing solid and it stays gooey (gross)
    • Non-Rubber Like properties: the addition makes the rubber conductive, but it sacrifices the material properties that make silicone great, like bouncy, stretchy, and flexibility. Many additions (like the standard carbon powder technique) can leave the silicone
    • Smears: The little bits of powder can stay on the outside and leave you with a rubbery bit that you don't really want to touch because it keeps getting nasty black smears everywhere.
    • High Resistance: often with many of these DIY techniques, one can only get the rubber a little bit conductive, with quite high resistances (>100mOhms)
    • Platinum Interference: This is one of the trickiest problems! Sometimes techniques that work for tin-cure silicones (like cheap Home Depot Caulk) don't work for nicer Addition Cure silicones (like Platinum Cure). You can keep adding Carbon powder, and while it will be conductive when still wet, once the silicone cures, it completely negates the conductive properties of the added element. My guess is that somehow the silicone is surrounding all the individual particles and insulating them from each other.
    • The Solution
      The best solution I have found so far (and please share any solutions you have come across), has been to incorporate Chopped Carbon Fibers. These are short little bits that people add to epoxy to increase the strength of the glue, but it also happens to be quite conductive! Another important factor is that unlike the graphite particles, the platinum-cure silicone seems less able to render it non-conductive. The hairs are also thin and small enough to keep all the nice properties of the rubber intact!
      Some papers and links that have helped me think about ways to make DIY rubber over the years:
      http://link.springer.com/article/10.1007/s00779-01...
      http://www.gillesbailly.fr/publis/BAILLY_ISkin.pdf
      http://cmd-www.dowcorning.com/content/etronics/etr...
      "Similarly, adding nickel-graphite, silver plated aluminum, silver plated copper or conductive carbon will make silicone electrically conductive. These various forms lend themselves to a sundry of applications including gaskets and pads for analytical instruments, handheld data devices, airflow management equipment, medical diagnostics devices, high tech gadgets, and other applications in the aerospace, defense, telecom and automotive industries."
      http://siliconesolutions.com/electrically-and-ther...
      https://books.google.com/books?id=bUdNzaeVGJkC&pg=...
      http://www.currentpleasures.com/collections/conduc...
      All about playing with silicone in general: https://www.artmolds.com/pdf/Silicone.pdf
    This article was originally published in forum thread: High Performance Conductive Silicone started by normnet View original post
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