Who wants smaller magnetic implants?



  • They actually have a number of different coatings besides the Ni-Cu-Ni.  They also do zinc, silver, gold and epoxy.  I only had them quote the Ni but it didn't take them long to get back to me. I could have them price out Ag and Au if that would gather any more interest in these. Also I could have a few other sizes as well. Let me know what coatings/sizes you are all interested in and I will get another quote with those.
  • Wow; if they're that cheap, I might put my name down for at least 50 of them.  In all honesty, I probably won't need that many, but it'll be nice to have some extras to experiment with, or in case some of them break.

  • I know Haworth implants are Au coated. I also know if anyone plans on implanting these in others that Nickel allergy is fairly common.

    Au quote would be great.
  • Ok, sent out request to see what Au coating does to the cost. I also inquired to the method they use to apply the parylene coating so we know if it may be prone to holes or not.  On that note I found a company who produces a DIY PTFE coating for parts that is bio-compatible and can be bought in either a liquid for dipping or a spray. Although they want me to call them to discuss my application to find the best fit for my needs, that said anyone have a good line of BS to sell them because I'm not thinking they will like my answer of using it to coat magnets to put into myself.  It also can be heat cured to make the coating tougher and it cures at 305C and the Nd magnets low end Tc is 310C. So it may be possible to cure the coating and not destroy the magnet. 
    Thoughts or comments?
  • PTFE undergoes pyrolysis at temperatures above 250 degrees celsius, releasing toxic compounds.  Is it claimed to still be biocompatible after curing?
  • Nevermind, after looking over things again I noticed that it states that it is not to be used for permanently implanted devices.  Not sure how I missed that over the first couple of reads, sorry for that.
  • Ok, I have received the revised quote for the magnets with a Parylene coating over Au over the Ni-Cu-Ni.  The price increase was a whopping $.02 per magnet for a total of $.38/each. I have asked about just a gold coating but from looking at their site the standard Au coating is this four layer coat. I would think this would be enough the help shield against Ni allergies but I'm not sure.  
    Also of note the method they use to coat the magnet with the Parylene is LPCVD which is done at room temperature.  

    There is $150 min order + shipping, so that is at least 395 magnets. Is there enough interest here to justify placing an order? There is also the 7-9 wk lead to keep in mind since they will be making these to order.
  • Definitely; I'm still in for at least 50, like I said.  Also, if we're only 10-20 or so behind the minimum order, or behind the minimum for a price decrease, I can increase my order, as well.
  • I'll be in for ~50 too, depending on how many magnets others are ordering. I can buy more if it's need to get the group buy going, but I honestly don't need that much. I'll do anything to get cracking though.  
  • Well that's 100 between two people plus I'll probably keep around 50 myself so I think it's safe to say I can get rid of these if I were to go ahead and buy them.  Also the ~400 is just a minimum but the next price drop isn't until 1000pcs so I doubt we'll get that far and it only drops the price to $.35, so it doesn't drop the price enough to warrant an increase in 600 pcs.  I'm going to post a new thread for a group buy so there is the possibility of more people seeing this. If that's a bad idea then a mod can delete it and I'll just stick to this thread.  
  • That sounds like a pretty great deal. I wonder if they can make 1/16" x 1/16"  (~1.6mm x 1.6mm) magnets as well. I've posted quite a bit on why I think that smaller will be better, down to about 1 mm on a side. This could be great opportunity to buy and test magnets that would likely be more sensitive and safer. 

    @extrion76 How would you feel about asking for another quote for 1/16" x 1/16" magnets? We could see how the price compares, and whether people would be interested in buying those instead of the larger ones. If you'd rather not, I might contact them myself and look into organizing a separate purchase.
  • Is it possible that by having the magnet longer on one side it allows better feeling? My understanding is that by having a cylinder the longer side will be implanted under the nerve, giving a larger surface area for the nerve to be vibrated. I could be wrong, but is that small of a decrease worth the difference in surface area?
  • @Cerasi - The company is K&J Magnetics and they have 1/16"x1/16" in their normal stock so I don't see why they couldn't do them. I liked having them a little longer on one side thinking that the movement may be a little greater.  They had a $150 min order per size and looking at the non-coated prices I imagine they would be cheaper as the size I was looking at are $.14 and the size you are looking at are $.11 each. I have sent an email about the 1/16x1/16 size, man I think I am probably driving this poor guy crazy. :)  He has been pretty quick with responses so hopefully I will be able to fill you in later today. 

  • My guess would be that a longer side increses the strength due to leverage (hope this is the right term).
    Also I see the point in having smaller magnets and therefor higher "density", but (again just a guess) I'd think they mainly differ in the range of frequencies. So smaller magnets --> higher frequencies, bigger magnets --> lower frequencies, as a general direction.

    That said I guess I'd be in for 20 magnets, not sure which size, though..

    (main advantage I see in smaller magnets is them being more robust to breaking)
  • @Cerasi, got the answer for the 1/16x1/16 magnets, all specs the same as above they come in at $.32 each, so minimum order would be 469 magnets.
  • @extrion76 Wow, they respond quickly. Good to see that we don't have to worry about much of a price difference. 

    @Jackthetripper It's totally possible that using a magnet that's longer than it is wide could increase sensitivity. A long magnet will want to rotate like a compass needle when it's in a field, so the ends would press on tissue/nerves. A magnet that's more square won't do that as much.

    Possible downsides:
     - if there was a really strong field and the long magnet flipped all the way around inside your finger, it would do some damage. Probably more than a square magnet would.

    - as @Ben pointed out, long magnets are a bit more likely to crack or get crushed, but who knows how much more likely.

    And then there's differences in surface area, and field to mass ratio. I dunno how all these factors balance out.

    I wonder if we could look up the mechanical properties of fingertips and try to model how different size magnets would respond to different frequencies. Then we could design magnets that would be most sensitive to certain useful frequencies, like 60Hz. I'll look into that.

  • @cerasi:  I think that a good approximation would be to approximate the inside of the fingertip as a fluid, though things like the average density, fluid resistance, etc. would either have to be looked up or determined.
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