various questions (mostly RFID and magent related)
  • So I've been lurking a few weeks now and I have a few questions I couldn't find on the wiki or forums (may not have looked hard enough though, apologies in advance). I'll try to keep this organised so try to bear with me here, I feel that these questions may warrant multiple posts but since I'm new I don't want to post a whole lot of stuff and clog up the new threads page. Let me know if I need to/ought to/can change this later.

    1] what is the highest storage capacity passive device currently being made that's reasonably implantable?

    2] do implantable magnets 'die' or fully loose function over long periods time/use? I read some posts about people saying there magnets died a few years after implantation and want to know if that's normal/common. (answer probably wont phase me from wanting some, just curious)

    3] Are there any advancements towards powered sub-dermal/internal powered electronics? In terms of surgically implanted power sources that rely on life span outlasting their host I know pace makers use uranium batteries but from what I understand they're super bulky as all hell, and in terms of non radioactive batteries I've heard of passive powering (nfc/rfid, currently inefficient for powering advanced devices) and /I think/ I heard about the possibility of thru dermal contact charging.

    4] I know this is more of a theoretical, but is there any chance that in the next few decades there will be displays flexible enough for sub-dermal implantation? I'm not talking about displays as complex as multi-color pixel based systems, but more of like a digital clock display where it has parts that in different combinations can make basic characters like letters, numbers, and punctuation. I'm picturing a sort of simple sub-dermal display that projects light thru the skin (say on the inner part of the lower arm) that reads out things like current time, internal body temp, blood pressure, etc.
    like, imagine that classic red number alarm clock display, only it's staring up at you through your skin and powered internally.

    I know its a lot, and If I need to split it into separate posts just let me know. I'm kind of a noob when it comes to this kind of stuff, in fact, I actually just ordered my first implantable and am waiting for it to arrive. Its a dangerous things xEM tag. IM SUPER EXCITED!!!
  • Welcome welcome, @Radon86.

    1)    The passive off-the-shelf device with the largest storage would be the flexDF from Dangerous Things but that is still in beta testing. That has 8K of EEPROM.
    2)    I have heard the same thing about magnets. In fact, I thought my own magnet had done that but it turned out that it was damaged and covered in scar tissue. Here’s a more detailed explanation. [LINK]
    3)    It sounds like you’re up to date when it comes to subdermal power. There are up-and-coming technologies that we all hope will change that.
    4)    Flexible displays are already a thing. OLEDs, in particular, might fit the bill of what you’re talking about. Have a look at those and let us know what you’re planning.
    Hopefully, other experts will chime in here and correct anything I'm misstated.

  • Some additions:

    3) Batteries: you can get rechargeable batteries with lifetimes surpassing your own. There are companies specializing in space and medical battery applications. Enersys is one of them. Those usually are expensive but no surprise there I guess. 2nd best option would be industrial grade stuff. I'm currently investigating NiMH coin cells. There are pretty robust variants out there, reasonably sized and good enough for a number of applications. Consumer batteries fall a bit short on lifetime and general quality, so I would not exactly recommend them, maybe with a few exceptions but generally better avoided. Things you should stay away from under any circumstances are no-brand random unknown quality batteries. Not in your body, not near your body either.

    Internal power sources: There are a couple of radioactive based batteries. They aren't quite as bulky as one would imagine. Like regular DIP and SMD packaging is available for easy integration into circuits. Last time i checked they were about 4k pre piece and the power output is pretty low. They are good enough to power a heart rate monitor or time keeping, but as soon as something requires actual processing power they are too weak.

    External power and charging: Resonance inductive coupling power transfer is currently the most reasonable choice. This is done for charging smartphones too but for use as implant you'd want to use a smaller scale version with less total power output for safety reasons. Quite a fun thing to build and toy around on a workbench.

    4) looks like you'd want something like a 14-segment display. They are available as single package per digit, or you can create led-arrays yourself on a flexible PCB and get it coated in flexible silicone etc bla bla.  The reason why subdermal displays aren't a big thing is cause they eat energy for breakfast. Like even a single small low power led can easily eat several hundred times more power than the rest of the implant combined. Which means you need bigger batteries etc. The better solution would be to directly interface with the body via low current pulses. It's way more energy efficient and does not require you to actually look at 
  • The low current pulse idea reminded me of an idea I had that I never tried yet.

    I would recommend experimenting with a wearable device before considering implanting anything but that's just my own preference.  Wouldn't need to be biosafe and size wouldn't be as big of a concern.  Once perfected, you could then work on making it smaller and coating it in something implantable.

    I have used a TENS device and noticed that different frequencies or patterns have distinct feelings to them.  My untested idea was to make an array of contact points and control which points are activated.  I think you could learn to interpret the pattern similar to braille.

    No doubt a lighted display would be way cooler but you wouldn't need to look at a pulse of electricity to get the feedback.  Even an hourly pulse might be useful.  Like a chime on a watch except nobody but you would hear or feel it.
  • 2. On it's own, NdFeB magnets should hold their magnetism long after you die. The core of the magnet itself should never be receiving damage or misalignment to it's lattice. :D

    Scar tissue buildup can create less nervous tissue to sense with, this might degrade sensation... But the magnet itself isn't getting any weaker ^^'

    If the coating is compromised and the actual neodymium is exposed, the body will degrade it; this will cause heavy metal poisoning and probably a lot of painful reactions... as well as a slight degrading of magnetic performance due to the metal being broken down and the lattice being decomposed. :v

    Extremely strong magnetic fields could also damage the magnet, but you will probably have worse things to worry about. The same is true with heat exposure. ,x_x

    If all things are proceeding happy, I don't think there's any reason the magnet itself should 'die'... But that's not considering the body trying to adapt to it, either. 
  • shame your experimental magnet failed McSTUFF, that scar tissue piece looked pretty gnarly.

    surprised that radioactive batteries are smaller than I first assumed, too bad they can't do much.

    In terms of 'wireless' or contact charging I think it would be interesting to see how far you could go with something like the batteries used in smart watches (used to own a moto 360 before the battery wouldn't hold consistent charge  *^* ) the battery lasts a good 8 hours before it needs recharging, I imagine a low power sub-dermal circuit could last a while on that kind of power, but i'm not sure if contact charging would work through the dermis and I'd be a bit iffy about using the same brand of battery seeing as that was the failure point on my watch and this is more something you'd want in at lest semi permanently (few years at least). If it did work though, I could see some type of recharging device, like a contact charging bracelet, that the user would wear at night during sleep.

    Sad to hear sub-dermal displays would eat too much power to be plausible but hey, who knows where technology will end up in a few decades. Saw a post where a guy was trying to implant a passive nfc powered led with a long wire extending between the led and the circuit, wonder if in the future that could be augmented/enhanced by routing the light through little fiber optic cables, like those little fiber optic lamps I some times see, to make a sub-dermal design that only lights up when powered. 

    My main interest in the idea of a sub-dermal display is less personal and more out of general interest. While I'd probably never get one, it would be interesting thinking about what type of application it could benefit, like maybe a fully internal heart monitor that constantly outputs bpm of the heart on a display through the forearm. In all reality it probably wouldn't ever /have/ a practical application. It'd probably only lend its self to some bizarre future aesthetic trend that no one would be a part of or more likely a bad sci-fi element. Anything a sub-dermal display could do a smart wrist display or phone could probably do better without going under the knife. 

    although... I remember reading a while back about a similar concept where there was a procedure you could undergo where you could get a re-writable tattoo. It was probably fake as I haven't heard about it since but it looked like the concept was that you get a big square tattoo of special ink that was comprised of a magnetic particle (or something like that) that showed up black or transparent when deactivated. The concept was something like you use a wand connected to your computer and you wave it over the area where your ink is and it changes it to what ever black and white or transparent and black image you load into the accompanying software. So the tattoo could be any solid single color image (black) that fits the programs constraints, or you could fully turn off the ink and your tattoo would be 'gone' as if it was just blank skin.

    Again probably fake, I haven't  about it since. If it is real, or you know a page that explains it let me know.

    Found an interesting post on here about someone experimenting on a high memory wireless comunicating sub-dermal implant. will have to keep up with that.
  • @Radon86
    Here's a thread about those tattoos.

    Yes, it is fake but would be cool if someone actually figured out how to do something similar.
  • Quick additions on betavoltaic batteries. sells those things. Smallest model is LCC44 (about 16x16x5mm). Their output power is somewhere up to 5 microWatts. That's good enough to keep the RAM of an attiny intact when the cpu is halted, but it's not even enough to power the watchdog timer, or any other oscillator for that matter.

    Inductive coupling easily gets you several, up to dozens of milliWatts. Even with silly simple and inefficient circuits such as a modified joule thief. Demonstrated in this example:

    As for how long you can go on a single charge. The coin sized NiMH batteries I play with have 43mAh at 1.2V. That's about good enough to light a small LED for a few hours. Alternatively you can have an attiny running for about a week on it (with the cpu actually beeing active). Using electrode outputs instead of fancy led displays you can buzz yourself the time as morse code every few minutes and hardly reduce that overall runtime.

    Subdermal led displays can be friggin cool looking. Imagine strings of blue-ish or green led running below the skin with simple animation. Like deep-sea creatures and their biolumini-spectacle. Someone in on this? building it would be stupid easy. Just led's in teflon tubing  and a tiny battery compartement.