let's talk about implants

i work in a lab that has mostly specialized in biologically inert non-fouling surfaces. basically, implants that don't need a workover every handful of years, and no need for blood thinners... i'm talking no rejection implants. 
silicone is only good for some things and PEG/etc is no good, we all know that.

implants of any decent size usually require these things (cleaning / thinners) due to platelet / stuff attachment to their surfaces as the body tires to de-integrate with them.

do we have any chemists here? can anyone do click chemistry or ATRP grafting? if so, i have some interesting things for you guys to try out in your next implant attempt...


  • I'm an amateur everything. My interest is perked, please expound (in layman's terms if you will, with perhaps some links to the nitty gritty once I've got a grip on it)
  • Several of us here are interested in better bioproofing methods for implants, especially those that can be applied outside a fully equipped lab. Please post your ideas here about what's available yet within the skillset of an amateur.

    Anything requiring greater process control than this would probably need to be jobbed out to a facility that applies such coatings. If you know of any grinder friendly facilities willing to do this for a reasonable price, please pass the word on about that too.

  • most implants work best if the polymer coating is grafted on instead of spray coated on. this means that the surface of the object is functionalized so that molecular structures can be grown right onto the surface.
    here's a review paper for anyone that interested :

    however, i do know someone who is working on creating a spray coating that can be applied with an airbrush and works better (and is safer) than PEG. this may be a bit more in line with what people are looking for. it's... never been tested inside people though. rats and oceans only so far (the ocean being a highly organic filled saline environment, like our bodies). it's only been applied to flat surfaces. i could talk talk with him about coating something with edges.

    any suggestions on things to try coating?
  • @glims: Coat some small electronics, a lot of people here (myself included) are pretty interested in the idea of having implanted bluetooth, wifi, etc.

    Bonus points galore if you can find, and coat, a bluetooth headset (or other small audio receiver) that also has built-in wireless/inductive charging. That would be a godsend to the community.
  • we'll start w/ some random electronics just as proof of concept. if it can coat calculator guts then it can coat any analogous surface.

    i found an inductive wireless charge receiver patch for about 10 bucks. if anyone wants to strip down a bluetooth device, attach the patch and then have it "goo'd", i'm down. lets go with the proof of concept first tho and just glom some random bits.
  • i'd advise against randomly coating electronics and implanting them. most devices are not designed to be implanted. starting from the power consumtion, over safety aspects up to reliability problems and buildin breakpoints.
    for testing out the efficiency of coatings i'd suggest using a dummy which also allows you to test the coating itself. like having a non toxic plate with markers for humidity on it.
  • you know, i was thinking about this. i think the first step would be just to encase the entire thing in silicon,cause yeah, many breaky bits.

    i'm pretty comfortable with the efficiency of the coating. the paper is in review right now. it's more of a 'this stuff is really awesome but maybe not approved yet' kind of thing. also, using this coating method on three dimensional objects is untested at this point.

    any other suggestions or ideas?
  • for coating. with the current circuit i design i plan to use the PTFE shrinking tubes sold by BOLA. with PTFE end-caps (containing additional stuff like magnetic coupled connectors or electrodes). simple, easy, cheap. a bit restricting when it comes to the cicruit board dimensions but that's not a deal-breaker. only point of failure i see with this approach is the thightness of the end-caps. having a humidity sensor checking the inside of the implant, giving early alarm in case of a leak would be a valid option. another way would be to build a liquid detector right into the end-caps. it's just 2 wires and one resistor. doesn't give the early hints but certainly alarms you when the ptfe-enclosure is defective.

    this approach was mostly chosen for the availability of parts, ease of handling and the benefits for prototyping. as the implant will be removed after a certain time of implantation and taken apart for analysis.

    guess the ptfe tubes or rods could be coated aswell, for experimentation purpose.
  • so, in place of inductive charging, wouldn't this be a more viable method, using cellular potential to create electricity?

    full paper is in the library now for people who can't access.
  • I'd highly recommend an encasement of some sort before applying silicon. Small bits will slowly wear their way through the silicon. The encasement needs to be something that will not shatter on impact and careful attention also needs to be given to sheer lines. There are a lot of factors that go into this actually.

    This is a lesson learned from lovetron experimentation and the Berkley course on medical implant design. But if we are just doing a test on material compatibility then an empty bic lighter might work.
  • with inductive charging we can easily get power transmittion in the range of 100mW and more. for the implant in development i target about 50 to 100μW. the inner-ear battery delivers single-digit nW. that would miss the target by a factor of about 100000. besides the inner ear is pretty difficult to access without cutting through a lot of bone , not to mention the posibility to damage it. interesting thing tho if there are more places to get such potential from.
  • @ThomasEgi i was thinking that since they are using cellular potential to get the energy, i am not sure that this method is ear specific. i remember some researchers did this sort of thing with trees... i guess you would need to get the cells linked in parallel to get the juice you need tho. not very plug and play :/

    @DirectorX empty bic lighter sounds like a great starting block. i'll get on it. 
  • Actually, I have a paper that Kevin Warwick (the same one from Project Cyborg) co-wrote on the use of inductive charging for the purpose of powering implants.  His technique is, obviously, not very different from how inductive charging is normally implemented, but it's nice to have some hard numbers on this application.
  • Added paper to library.
  • Yeah, that's the one.
  • @glims well if the power output increases with future development it may be worth a shot. but for now it's of no practical use for grinding. using subdermal solar cells or piezo based harvesting of kinetic energy appear to be a lot more promising.
  • that reminds me, has anyone considered implanting a piezo system? those crystals are really easy to make, but i have no idea how large they would need to be to make the power you need.
  • the problem i see with piezos are or physical nature. the power you can harvest from mechanical motion is limited to the force*distance over a certain amount of time. and in case of a piezo, the distances are usually just a few micrometers, or a couple of millimeters at best. so you'd either have to work with high forces (like putting them in your shoes where the entire body serves as force source) or you have to shorten the time span of each load/unload process (or in other words, finding a energy source that emits vibrations at higher frequencies).
    since no one is shaking his arms 200 times per second, or even 20k times/s. that's not entirely ruling out piezos as such, but it would require to come up with a design that compensates for those issues.

    by increasing the available path a mass can move to several centimeters we'd be able to get away from high frequencies. the basic options would be either a tube with magnets sliding through it and a coil wound around it (like those shake-flashlights). or a magnet that rotates over a ring of coils (very similar to what mechanical self-winding wristwatches do).
    the linear version is rather easy to build but in terms of power output i'd go with the rotating version as it picks up a wider range of motions.
    construction of such a rotating generator is a lot more complicated and may even require micro-gears. so i'll leave this up to some dedicated precision engineer.

    last but not least we have solar panels. if we keep the circuit boards single-sided. we could use the other side to directly mount solar panels to it. there are excellent circuits to help harvesting energy from low-power solar setups. for an implant location that's exposed to daylight/sunlight and rather close to the skin surface that's certainly an option worth trying out.
  • @ThomasEgi I've been working on the magnet/tube idea since we first discussed it, and I had a question: what do you think of capping the ends of the tube with piezos? Most diy magnetic generators use weaker magnets at the ends to prevent the magnet from smacking the end of the tube, but is there any reason we can't harvest that energy too? My current design uses a 10x5 mm neodym btw.
  • @Saal seems to be an option. altho that's a pretty harsh mechanical crash you run into there. not sure if that kind of impact and potential lifetime reduction is worth the energy you get out of it.

    the design is a difficult question. a tube that runs in parallel with the bones would be probably be suboptimal since (my guess) most motion happens along the "thumbs-up" axis (of the arm/wrist).

    getting some data on this would be very useful in optimizing such a generator.

    so... to all smartpohne owners out there ( SMARTPHONES REQUESTED): please download some acceleromater logging app, attach the phone to your wrist/upperarm/torso/legs/wherever and log the data (whatever timeframe suits you). also please attach what axis the data correspond to.
    like for the wrist: https://en.wikipedia.org/wiki/Right-hand_rule

    i'll try a bit of logging myself with a wii controller i have around. the more data, the better.
  • I have the "Data Collection" app for iOS, and I'm pretty sure it allows recording/exporting of sensor data. I'll see what I can do at some point today/tomorrow.
  • edited August 2013
    it may not be the most scientific way and there may be people claiming there are good and bad ways to get hands on acceleromation data.. but if you ask me.. screw that and hand me the damn tape already.

    slapped together a small python script logging it. if someone is interested i'll upload it. logs the data to a file, and allerts you with the pager motor in case the battery is near-empty (below 25% in my case)
  • I have wiimotes, tell me what to do :P
  • http://home.arcor.de/positiveelectron/files/logaccdata.py
    install python and the python wiicd library. and
    python logaccdata.py
    press 1+2 on the wiimote as prompted on the terminal.
    if it connects it should run a test on the rumble motor. then it should create a logfile with x,y,z data. dividing those values by 10 will get you the acceleration in m/s²
    if the battery goes low it'll rumble you aware of it.
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