some magnet implant related questions

edited February 2015 in Magnets
I'm intending on installing a set of magnets in the relatively near future and am assembling materials. There are, however, a few questions I have remaining before I sugru the magnets and install them.

first is relating to magnet size, position vs sensation. my intent is to use long thin cylinders, about 1.5mm x 5mm with poles at each end. I intend to place them in my ring fingers on the side opposite my thumb on each respective hand. my intent was to keep them in a nerve rich area, while keeping them out of areas that get touched and messed with a lot. I have noticed that disk magnets appear to be the standard - does the size and shape of the magnet significantly affect the sensation that the final implant will deliver? if there is not an appreciable reduction in sensation due to the use of smaller magnets, I may even try out magnets as small as 1.6mm x 0.8mm (disks). similar question regarding positioning on one's fingers - will my choice of implantation site have any major effect on the sense?

my final inquiry revolves around the recent interest in the use of medical grade implants rather than DIY ones using sugru. my understanding is that some implants using sugru failed and began to degrade. did this occur due to the sugru breaking down somehow, or was this an issue of an incomplete or damage coating?


  • Considering my recent experience with my implant includes it turning end-over-end in the presence of a large magnetic field, I'm incredibly thankful mine is roughly cubic (cylinder section about the same height as diameter, if you see what I mean). No pain resulted.
    A 5mm rod sounds very long; I'm not sure how it would impact use of the finger, or be in danger from your environment. I've rock-climbed a (very) little since getting mine, and it's stood up to it; mine is almost in the centre of the pad of my finger, though, so I might be at a higher risk of damage or interfering with my use of the finger. Also, the sense works through mechanical movement of the implant, and the bigger the implant the stronger the impinging field has to be.
  • so smaller magnets are more sensitive? I suspected that might be the case but I wanted to ask. in that case perhaps the sensitivity of a given magnetic implant could be rated at surface area exposed to nerve rich area over implant mass? probably some constants in there somewhere too. I'm not yet convinced that is going to be the whole story - this implies that a large array of small as possible magnets spaced just far enough not to appreciably mess with one another is the best option. perhaps I'll try several different sizes and take some observations to see if I can't fill in some of those constants. do this mad science style rather than just mad engineering =D

    in any case now I need to order those smaller disks now...
  • Arrays of multiple magnets have been tried - one "Haworth implant" story involved 4, a magnet at each "corner" of the fingertip. I can't remember how that one worked out.
    I don't think surface area matters; mass and Teslas (magnetic flux density) are what I would think are the important ones.
    Again, please count the weasel words in my comments before deciding. ",)
  • well then I suppose I will stay away from the array idea for the moment. I'll probably just stick to the tiny disks and sugru.

    the reason I mention surface area is that it stands to reason that the greater the area of nerves that your implant is stimulating, the greater the sensation that you feel.

    (also I think you may mean magnetic field strength. I'm about 60% sure that magnetic flux is measured in webbers rather than teslas)
  • @silver7017:  magnetic field strength (i.e. H-field) is measured in amp-turns per metre.  While magnetic flux is measured in Webbers, magnetic flux density--roughly, the magnetic flux divided by the surface area--is measured in Teslas, and is what corresponds to what most people think of as the magnetic field (i.e. the B-field).

    Also, there was an idea a while back about stacking magnets N-S S-N, or vice-versa, to see if that gives a greater effect.  I think that the discussion at that point remained inconclusive, though.

  • The only stacked magnets configuration I know of was... *to the Internet!* ...yes, it was one of Shannon's implants - who turns out to be the person who got the four singles, too. See here for how they turned out, though Shannon got early-generation implants; they use more thorough bioproofing now. I'd worry about stacked magnets; I'd feel the lack of mechanical solidity in the implant would allow movement which might contribute to a bioproofing breach.
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