New electrodes

Have been messing around a lot with EMG lately and one of the biggest problems I've faced is with the electrodes. Currently all the electrodes available on the market are disposable wet electrodes that generally only last for one use which is a problem for ongoing projects I'd like to be longer lasting and is also a hassle to have to try and find the exact same spot again every time so as to not skew the results.

The way I see it, there are two main options to get around this issue. Either to come up with cheap and easily manufactured reusable dry electrodes or to design small implantable ones. I think the former solution would be easier but I have no idea how to make that work. The implantable ones would be a lot easier said than done as you'd have to make them wirelessly transmit the data and because of the small size would likely have to have them wirelessly powered as well. And then you still have to ensure that they're both conductive and biocompatible.

Anyone got any ideas or suggestions?

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Comments

  • Implantable EMG sensors have already been developed.
    https://www.ncbi.nlm.nih.gov/m/pubmed/18002310/
    Unfortunately, it would be some serious work to make your own. Conversely, they also make reusable EMG sensors, but I don't think they meet the low cost requirement. While it's not a trivial task, it would be much more achievable in my opinion.

    That said, I'm all for making implantable EMG sensors, especially if you have the tools, skill set to pull it off, and the time to devote to the project.
  • I think an easier solution would be to figure out how to make your own conductive gel. Metal plates work fine unless you're trying for active electrodes. I'm sure you could mod the open eeg projects active electrodes to work this way.
  • I've tried out stainless implants to facilitate muscle contraction. Some of the signal would leak across skin and hurt like hell.
  • @Ironalex @Cassox I'm currently working on two versions to see if I can get anywhere with either. First is a reusable dry flexible electrode using conductive polymers and second is an implantable one.

    With the dry one, I'm just working on a better design and and a better composite material for the electrode itself as the polymer I'm using unfortunately is powdered and insoluble. Should have a prototype done within a month or two hopefully.

    The implantable one is still very much just a concept however as I still haven't figured out all the details or got the estimated size down small enough. @Cassox , you have quite a bit of experience with bio-compatible coatings, right? Do you have any ideas as to what might work for an implantable electrode? I'd imagine you'd either have to go with something conductive or find a way to integrate the electrode surface into the outer coating whilst having the whole thing still properly sealed.

  • I hope the new electrodes will not be sticky too much and will be painful once you remove it. :)

  • You could use something like this reference design for communication between the implant and a phone:

    http://www.ti.com/tool/TIDA-00217

    Put these two chips (NFC controller and low power MCU) on a 0.6mm thick PCB with some kind of convex electrode mounted. Read the analog signals off of the electrode with the microcontroller. If that's not precise enough, maybe use the ICs used on this sensor:

    https://www.adafruit.com/product/2699

    Once everything is working to your satisfaction, pot the whole thing in the biopolymer of your choice, leaving part of the electrode exposed. It might end up a little large in the X-Y axis, but short in the Z axis.
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