Conductive filament means printable sensors

The 3D printer world has the creation of plastic trinkets pretty much down pat. The next step, obviously, is the creation of multi-material models, whether they be made of two different colors of plastic, or completely different materials entirely. A few folks from the University of Warwick and GKN Aerospace in Bristol, UK have come up with a way of putting electronic sensors directly into 3D printed objects.

These new sensors rely on a conductive filament custom-made for this study. So far, the researchers have created flex sensors, capacitive buttons, and a ‘smart’ mug that can sense how much water is contained within.

To produce their ‘carbomorph’ filament, the researchers stirred regular old carbon black to a sample of polycaprolactone dissolved in a solvent. After shaking well, the mixture was laid out on a piece of glass for an hour resulting in a thin film that could then be rolled into a 3mm filament. While this is a great way of producing small quantities of carbomorph filament, we’re sure a few Hackaday readers can come up with an easier way of rolling their own conductive filament. Send us a link if you’ve figured out a better way.

Tip ‘o the hat to [Evan] for this one

Comments

  1. Paul. says:

    Multi layer pcb’s for the hobbyist?
    Arduino’s integrated in a teacup?
    Sounds very promising for a lot of stuf, but I hope the polycaprolactone is only for the prototype becasue it’s not very suitable for your cup of tea.

    • squalyl says:

      Let’s think bigger : 3D circuits !

      • John says:

        Sorry if this comes off as rude, but what do you mean by “3D circuits”? Isn’t that just a multi-layer PCB? Do you mean placing electronic components in 3D space? Wouldn’t that mean many components would have to be redesigned to better the utilize space and be “3D” as well? Would it actually save any space? Wouldn’t that just look like a rat’s nest and be a pain in the ass to test during production and for maintenance?

        Is there a meme or joke I’m missing? I’ve thought about 3D circuits too from time to time, but it always seemed so ridiculous (because of the reasons I listed and more) that I’ve just given up.

      • JB says:

        Wasn’t the original Terminator’s cpu made in a 3D process? :P

  2. sjl says:

    Hi guys, we never thought this would make HaD! Fantastic! As the article above says, we just made small lengths of filament to run through the printer for each run but we’d be interested to hear if anyone has any ideas for scaling this up to make longer strands.

    We went with an open-access paper so we could share our ‘recipe’ with the 3DP community and RepRappers to try and spark some ideas for cool things to try and make with it.

    If you’ve get any questions or want any pointers, just drop us a comment or an email.

    Si

  3. 0xfred says:

    Excellent. I’m sure the process can be streamlined – not necessarily for home production, but for filament manufacturers to churn out sell by the reel.

    I’ve seen a few dumb TV reports on 3D printing that always mention printing electronics despite it not happening at the moment. (“You could just print out your new phone”.) It’s good to see some small progress is being made in that direction.

  4. sjl says:

    Hi 0xfred, that’s the idea we were going for, we know it’s far from a finished solution but we’re hoping it’s a step in the right direction.

    Si

  5. Galane says:

    Stir up a large tank of the stuff then spread onto a large, rotating drum that’s heated to flash off the excess solvent. Scrape off the dried sheet and roll into a filament in a continuous process.

    Equipment already exists that can do this.

  6. chango says:

    Or just buy some from these guys: http://forums.reprap.org/read.php?94,134003,135436

  7. willaim says:

    i suppose its essentially the same as making conductive glue but pretty interesting nonetheless.

  8. Jehu says:

    Galane, you beat me to it. Was going to say the same thing. I’d probably use a different polymer though. Having to use Dichloromethane as the solvent probably wouldn’t be the best in the long term due to health hazards. Would be easier to use ABS and acetone as it’s cheaper and bit safer. Add a cutter to that drum and a fume extractor to recover the solvent and you good to go

  9. not really that interesting or new. They mixed up carbon black with polycaprolactone (PCL, aka polymorph), thought up a new name for it and printed some stuff. From what they printed or suggest as application you can derive the resistance of the stuff is quite high, only making it usable for cap sensing and other non-current applications. I would be much more impressed with printable filament with resistance in the sub-Ohm regions. Bonus points if it is solderable.

  10. Dug (@duguk) says:

    Related question – what is the easiest way to sense how much water is in a small container? Especially at high temperatures, it seems a little tricky.

  11. matt says:

    I wonder if you could design a hot end that would mix the conductive material just prior to extrusion. I’m imagining something like those mixing tips on 2 part epoxy bottles.

    Next step is to make semiconductor filament for printable logic

  12. AaronC says:

    How about a head design that included nozzle for powdered metal and a Laser. Then you could print in plastic as well as laser sinter the metal for traces, etc. That is assuming that the heating from the sintering was pretty localized and didn’t overheat the plastic too much. Would be fun to try anyway.

  13. Zee says:

    The resistance is way too high for any PCB printing

  14. Mike says:

    @JelleAtProtospace
    The paper quotes resistivity that is in the sub-ohm range: “The measured resistivity of the composite in-plane with the layers was 0.09±0.01 ohm m−1. Perpendicular to the layers, the resistivity was 0.12±0.01 ohm m−1″

  15. sjl says:

    Apologies, that should read as ohm.m as the units for resitivity guys, that crept through the editing process.

    I’ll get it amended.

    Si

  16. xorpunk says:

    Good luck giving negative criticism to this…

    This demonstrates how 3D printing hasn’t even remotely reached it’s potential in manufacturing and fabrication..

    Related note: It’s possible to also do phosphorescence filament that can make efficient lights that are periodically charged with a ULV LED…

  17. Michael says:

    how to join the metal leads of a capacitor or a resistor to the conductive filament?

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