Something new - 3D printed RFID and magnet injectors (I'm long-winded; sorry)

(The forum software is distorting the aspect ratio of several of the images.  The fullsize view should be correct, though.)

A few months back, a friend of mine bought a 3D printer.  I don't need to explain, I think, how cool having one would be.  He urged me repeatedly to buy one myself, but I just didn't want to drop the money for one.  But I did do some research on them.  I did not want to spend what he did on his (he bought an XYZPrinting Da Vinci Pro), but it kept itching in the back of my brain that I needed one.  Looking for a lower pricepoint, I read about at the Da Vinci Junior.  Unlike his Pro, the Junior, besides having a smaller print bed, will not print in ABS but only in PLA.  So I got to reading about PLA.  One article lead to another and another and another and so on.  Then I ran across this:

On the intrinsic sterility of 3D printing

Interesting read.  And it really got me thinking....

I've been sitting on a bunch of custom made n52 cylinders (3mm x 10mm); since the m36's are still not available, I sourced an alternative.  Still deciding on what final coat they should get (they are gold plated from the manufacturer, but I want to add another coat onto that).  And I'd still been debating the best way to implant them.

Combine those magnets that I've got sitting on a shelf in my living room with that PDF article I linked above, and I got the brilliant (and I use that word loosely here) idea to 3D print custom injectors for the magnets.

Let me say right now that I knew I could never print the needle part of an injector (not sharp or strong enough), so I quickly realized that they would require some assembly with a stainless steel needle and so the possibly inherent sterility would be compromised, but the seed was planted.

I ordered the printer from Amazon.  It was out of stock.  It took almost two weeks to come back in stock before it shipped.  I spent that time looking for the right piercing needles and running through many design iterations on the printed portion.  I ultimately bought needles from Painful Pleasures.  They list internal diameters of the needles (let me tell you, not all needles of a given gauge are the same size internally or externally; these guys list specific internal dimensions and wall thicknesses, so I went with them).  I got a box of 25 1.5" 6g piercing needles to fit into my theoretical injector design.  They arrived and it was then that I realized I didn't really want a length of printed PLA (the injector plunger) rubbing against and internal shaft of printed PLA (remember that 3D printers print in layers and prints are not perfectly smooth; I did not want flakes of PLA coming off while injecting and ending up inside me, even if PLA is more or less non-toxic).  So I decided I needed longer needles so that the needle would jacket the entire length of the shaft of the injector.  And because the 6g needles are frightfully large, I should start with smaller 10g needles and implant an RFID first.  So I ordered a box of 3" 10g needles (and a box of 3" 6g needles for future use), sourced and bought another NTAG, and went back to redesigning the injector.

The needles arrived, the chip arrived, and the printer arrived.  The printer, sadly, was DOA and had to be exchanged.  So more waiting (and more redesigning of the injector for good measure).  The replacement printer finally arrived.  I spent a few days familiarizing myself with the quality of the prints.  Then I printed an injector.  The design was reasonable but ultimately flawed.  I spend a week toying with the design and reprinting.  Many iterations came and went.  At one point I switched to a different spool of PLA filament and discovered that the shrinkage of this color filament was different than the previous spool (PLA, and ABS for that matter, shrinks a bit after printing, so you need to account for that when you're trying to make a hole in which something of specific dimensions needs to fit snugly).  More redesigns.  More printing.

Finally, I arrived at an injector I liked that printed nicely and fit the needles well (I worked concurrently on both sizes).  I got some supplies (91% isopropyl alcohol, chlorhexidine glucanate, gauze, band-aids, etc.).  I planned to inject more than a week ago.  But outside factors prevented it.  Tonight, I finally did it.

I implanted an NTAG216 with a 3D printed injector.


This is an image captured in Tinkercad of the 3mm injector:


And a top down view (there's a small lip at the bottom of the shaft to prevent the needle from being able to slide all the way through):

And here is a closeup in XYZWare after "slicing" the model (each layer in the image represents a physical pass of the print head; this was printed at 0.1mm layer height):

And here you see an injector mid-print:

And the finished print on the print bed (each print takes about one and a half hours):


  • edited February 2016
    The completed assembly:

    After the print completes, I remove it from the bed then use a spare
    needle inserted point first into the injector to clean out any PLA
    debris inside the shaft (twisting the needle back and forth removes any
    loose material). I then rinsed the whole thing with isopropyl alcohol to
    remove any PLA fragments.  After that, I insert a fresh needle into the
    injector and use a tiny dab of Super Glue to secure it in place
    (probably unnecessary).  Then I soaked it in alcohol for a bit, rinsed
    with saline, and wrapped the whole thing in sterile gauze for future

    Before implantation, I soaked the whole injector and plunger
    (which is the T-shaped piece) in isopropyl alcohol.  After a
    indeterminate amount of time (truly, I did not keep track, but roughly
    half an hour), I removed the injector from the alcohol, rinsed it with
    saline, inserted the chip into the needle, then using the same technique
    as I've used on all the other chips I've implanted, inserted the needle
    into my arm.  In this case, it's several inches further toward my elbow
    than my forearm LifeChip, resting perhaps a bit too closely to the
    palmaris longus tendon.  After the needle was at the depth I wanted (and
    note, this design exposes far more needle length than most injectors,
    so I did not go to the full depth of the needle under the tissue), I
    slid the plunger into the bottom of the injector and lightly depressed
    it while backing the needle out at the same speed (same as with any RFID
    injector).  I then withdrew the needle, used a piece of sterile gauze
    to wipe away the blood, and put a band-aid on it.


    there are some caveats here to be aware of.  I acknowledge that there
    are risks here that should probably not be taken.  Because of that small
    lip at the bottom of the needle hole in the injector, there is some PLA
    rubbing on PLA (though the "grain" of the plunger is perpendicular to
    the grain of the injector body, reducing the overall friction).  This
    could have resulted in some PLA fragments ending up being injected into
    my arm.  A design that did not have that lip might be a better option. 
    And it likely would have been better to soak the injector for longer
    before I implanted, and have used the chlorhex instead of just the
    alcohol.  The needle of the injector is larger than the one I've seen on
    mass produced injectors (only slightly bigger, mind you), so there was
    more damage to tissue than was really necessary.  Implanting in the
    forearm is probably not a wise choice (too much biology happening in
    that area to really be safe).  And I did not really need another RFID,
    and I really believe that one should only take the risk of implanting if
    it is something you have a real need for (well, or real "want", I
    guess, since at this moment in time, no one really NEEDS these kinds of
    implants).  And, hell, a whole injector isn't even really necessary. 
    All you really need is a piercing needle and something that'll fit
    inside it.

    That having been said, any time any of us are doing
    any of these kinds of things and sharing knowledge and experience, it
    moves us all forward.  In that sense, this little experiment was
    definitely worth the time, expense, and personal risk.  It opens up the
    possibility of using other gauged injectors for things like magnets and
    whatever else one can successfully slide through a needle without the
    need to have something custom manufactured in some arbitrarily large
    minimum lot size.

    I will be uploading an injector model on Thingiverse
    sometime this evening and linking it here for anyone who cares to check
    it out and maybe print one of their own.  Be aware that whether you are
    using PLA, ABS, or whatever other printing material, the fact that
    prints shrink by varying amounts from material to material and spool to
    spool, the bore size will almost certainly need adjusted.

    As soon
    as I decide what to coat the magnets in, I will be using a custom
    injector to implant one.  Or maybe I'll just live with the existing gold
    coating (thoughts, anyone?)  Either way, I will be following up with
    how that goes in this thread as well.
  • edited February 2016
    I'm not convinced that gold alone is not viable, but I do have concerns about it.  I am likely to get one plated in rhodium if for no other reason than to learn for certain whether or not it is a viable option.  I am willing to self-experiment (within reason; @Cassox mentioned that it might be a good coating for magnets awhile back, and I trust what he says).

    My concern with products like the one you've linked is in getting a smooth coating.  Flaws in the surface give anchor points for bacteria and detritus to collect.

    Thank you for the suggestion, though.
  • @aviin, did you ever upload the injector to thingiverse? The link just takes me to the homepage.
  • @ChrisBot - You know what?  I didn't.  I'll get them up there tomorrow and put a link up here.
  • @aviin, awesome thanks.
  • Here is a link to the injectors on Thingiverse:

    2mm and 3mm injectors are in there.  Enjoy!
  • Would suggest against Au alone, it's fragile and pretty easily compromised compared to parylene, TiN, etc. however, it is bio safe.

    It's like, by itself the absolute least you could get away with. >~< It's 'safe', but it's like... Making a pair of safety glasses out of basic glass. They'll break relatively easy.
  • @aviin, was it the Da Vinci Jr that you ordered? I was gifted one several months ago, but never manage to get a good block of time free to set it up and start playing with it. How do you like yours?

    I've read some people complaining that you have to use the proprietary printer spools with it, but others have gotten around that by hand-reloading the spools with different filament. The only caveat being that the printer supposedly gets its temperature info from the spool hardware, so if you re-load it with a different material that needs a different temperature, it might not come out right.
  • @katzevonstich, yes it is a Da Vinci Junior.

    I like it well enough.  I'd like to be able to print ABS, but since the Junior doesn't have a heated bed, that's not possible.  PLA works okay for my uses, though.  The spools are proprietary (and more expensive than other brands) and because of an NTAG in each spool that gets written to by the printer as it feeds filament to track how much is left on the spool, you can't just reload an empty spool.  A few people were close to having an easy workaround awhile back.  Haven't printed much lately, though, so I haven't looked to see how that's coming along.
  • So i'm looking to do an injected magnet implant but I will only be using a .75mm by 1mm cylinder magnet. That means I am only going to use a 16 gauge needle with an outer diameter of 1.26mm. Do you think I can just scale one of the models down, or do I have to try to design a new one? I'm not very good at 3d modelling so I hope I don't have to do the latter.
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