Creating bioproof, flexible wiring for the body



  • Yeah. unless the whole cable is gold, the gold ends somewhere, no matter what fancy alloying or deposition techniques you use. Then you're back to the corrosion issue.

    bioinert conductive polymers ftw. There are several silicone blends you could go with.
  • well it is possible to make a thight sealing between gold and some insulator. but even getting full-gold contacts will neither be easy nor cheap. even more so for gold contacts that can be properly sealed on the backside.
  • Reading through this discussion, it does seem to me that Shaedler's suggestion would be the most practical. My impression of the proposed technique was to mimic the way in which arteries continue to function while being non-elastic.

    If we house wires in a non-stretchable tube coated in bioproofing that the body does not bind to (except at certain anchor points), this tubing can have the necessary length for a fully extended joint, and can have a snake-like shape when not extended, without causing tissue damage.

    Since this was also suggested with a way of implanting that didn't involve a great deal of cutting (it's on the first page of this discussion for those that want to reread it) it definitely seems like our best bet currently.

    Also, since this is my first post: hello everyone, I am Nightgaunt. I'm currently a biotech student, so electronics is not my area of expertise, but I am definitely a fan of taking inspiration from nature as Shaedler has done.
  • When i was designing my electrode driver circuit i took the time to have a glimpse on what current commercial systems offer in terms of wiring and connectors. Turns out that my initial idea of using a ring-based system is awfully close to what is done in practice.
    Given they don't use conductive silicone, but stainless steel and platin-iridium. Aside from that it seems to be pretty much identical. Medtronic has a couple of implant manuals that can be found by googling, some of them contain drawings with dimensions.
    The actual wires seems to be nothing special, just a bioproof tube with regular wires in them.
  • shouldn't "regular" bioproofed wire work for short distances (say half a forearm)? Four copper braids twisted together like you do it with wire ends coated in Parylene or something like that. If the wire doesn't have to flex around a joint this shouldn't be a problem, right?
  • I wouldn't exactly recommend a parylene coating for this. If you use PTFE instead, the body won't bind to it, so it's easier to move and remove it. But yeah, if you keep the wire away from the body itself, this should be no problem. PTFE and FEP tubing are available as laboratory materials down to very small sizes. The biggest problem by far are the connectors.
    Using  316LVM stainless steel instead of copper would give you additional safety in case the coating takes damage. That stuff is hard to solder tho.
  • This isn't exactly in line with the topic but might relate to the idea behind the question. Instead of using wires some universities are researching Ultrasonic Communication between implanted devices because the human body is composed mainly of water. If it turns out to be feasible this would solve communication issues between implants but not power transmission. Although one *possible* solution to that, along the same lines, could be to use piezos(which might already be used as the ultrasonic transducers) with the same resonant frequencies...a little bit like magnetic coupling in existing wireless chargers but power transmission would be miniscule.
  • I strayed away from my original plan to go with Qi as inductive interface. At least for smaller implants it's easier to have a discrete charging circuit, which can also do bidirectional communication quite easily, while transmitting power.
  • What about adding small loops / circle shaped figures to the sides of the wire, parallel to the skin above?
    This would of course only make sense with Parylene and making the skin bind to the wire, but it would help keep it in place and make the wire not move to the sides, possibly ripping the tissue and probably causing a lot of pain.
  • edited January 2014
    I'd have posted this sooner, but I lost the link for ages, I'm not sure if the substrate they're using is bio-safe, but that should be easy enough to research and possibly replace if it's not. I'd be interested to see if it could be made to match the elasticity of flesh, if so, it could be ideal. 

  • Hi guys, new here - not got much relevent experience, but i'm more than happy to learn all i can.

     sorry for necro-ing, but I was reading a different thread yesterday (about tattoos as wiring), and a thought occured to me - why not use something like a scaled down endoscope to route a cable through the body? Shaedlaer said about two small incisions and a rod to make a channel for the cable to run through, well this would be similar. If you were to be able to cause the head of the endoscope to expand (like a bottle stopper kind of idea) you would be able to put it through a tube, expand the head to hold it in place in the tube, then route the tube through the body to where it needed to go.

    This could be done through a smallish needle. this would also allow the 'snaking' of the tubing to allow it to compensate for joint mobility, etc


    small endoscope to insert a PTFE tube under the skin, insert cable in tube.

    Not sure if this will help but thought I would bring it up.

  • Or why not do the wiring via skin piercings and use magnetic coupling for sending power and data to implanted devices?
  • we had that already:
    1. transdermal (even if it's microdermals, still transdermal)
    2. requires insulation (you don't wanna transmit power via bare wires)
    3. induction and wireless coms are just so much easier to work with so why risk infections and electrocution.
  • Coated of course - I wouldn't suggest naked wires!

    What I was thinking is this:
    You can get PTFE "stem" for piercing, people commonly use PTFE to stop piercings from closing up  - what I suggest is basically making a series of surface piercings using PTFE tubing, put your wires through that and stitch it in and out of the skin, interfacing with subdermal parts via EM induction.

    By doing this you could distribute power to all your implants from one place fairly easily. When crossing joints you just add some extra loose wire to enable flex.

    See my profile pic - the USB cable going to the back of my head is slightly long so that I can still bend my neck without pulling on the device I mount there - same basic principle.
  • Wires outside the body would become a zipper if you caught it on something. I once used the analog of catching a shirt sleeve on a loose nail and tearing. Same thing except human leather.
    Just think of commercials for Bluetooth headphones where people are struggling with their wires and getting caught on things.
  • Yeah. The whole extra loops of catch prone material is fine when you are sitting in one place but kinda falls apart when you are moving. Think about it like when you last smashed a finger and couldn't use it for a while. All of the sudden, every action comes with the thought, 'oh wow, i never pay attention to how important my index finger is'. Now scale that up to a 'wow, i never realized how much I brush against objects' level, and instead of casual pain, add tearing flesh....
  • Are you certain it would lead to a "zipper effect"? If the extra bits outside are flat to the skin surface there should not be sufficient room to catch on anything, which leaves only the excess over joints.

    I can picture this excess getting caught from time to time, but not so badly caught that you can't trivially undo it and carry on before it actually starts tearing flesh. Even if it does catch badly enough to hurt, the pain would be a good signal to undo it and provided it's pierced correctly you shouldn't see instant tearing of all your skin.
  • I guess it's mainly a person to person type scenerio because if I had anything out side of my body in that fashion it would last about 1-2hrs depending what day it is.

    My job and hobbies would Make this the most unwanted thing for me. For someone who is a little less active in movements and hobbies it may be an ok idea with cautions.
  • Yeah when you rock climb and longboard regularly, even normal skin has the tendency to catch on things and rip. Adding a line to it just seems foolhardy.
  • Started some research on slack in the channel #subdermal-wire. There is a lot of information there already, mostly manuals from Medtronic's series of deep-brain stimulation devices.

    They use silver core mp35n wire and medical silicone or fluoropolymer under polyurethane in various places. The connectors are stainless steal and use set-screws and terminal blocks.
    As I said, details on slack and help with digging through everything appreciated there!

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