E-paper electronic tattoo implant

Unfortunately I have not succeeded in connecting the display to the old adapter board, and this really frustrates me.
I think some of the pads on the board are bent or damaged, so I will order a custom PCB with longer pads to make soldering easier.
This also gives me the opportunity to get started with the storage solution I found.
I really hope I haven’t fried the display yet, it still looks in good condition but you never know.

Just wanted to let you know that I’m still working on this, I simply did not have anything interesting to post here yet.

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Thanks for the constant updates!

It’s nice to see someone putting good effort into a project they believe in! :grin:

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This is the new adapter board I came up with, I will look through everything tomorrow and check for mistakes, but this is the basic idea:


Notice the double 6 pin sockets, these are for interfacing with a NTAG I2C Test Card.
The pins next to the large pin block is for interfacing with the microcontroller of choice, the other 6 pin socket next to it will be used to slot in the NTAG I2C Test Card directly over the board.
This devboard also has the storage chip on it (in a larger package, the final storage solution will be wafer level) to get used to it.
The solder bridge that you can see is to enable or disable power harvesting from the test card (this can be used to test if the expected current draw does not overload the NFC power harvesting)

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I did not order the devboard yet but I will soon.
Could not find the time yet to make sure I got everything right, plus since I am still a student I would like to wait until next payday😅
Other than that: a new idea for a feature came to mind:


This is a pieroelectric disk, it vibrates when a current is applied to it.
This technique can also be used for energy harvesting, but that is not my intention for this component.
Since it only pulls 1mA I feel like this would be an excellent way to give feedback to the user for the placement of the phone/NFC reader.
Would this idea be feasible, or does this not comply with biocompatibility rules since vibrations can disturb surrounding tissues?

The white ceramic in those disks contains lead IIRC. And I don’t think that those would be very useful if encapsulated properly.

It’s probably easier to stimulate nearby muscles and could potentially require less energy as that feature would be mostly powered by the user’s body.

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I was not aware of this, seems like a accident waiting to happen if inplanting a lead disk this large.
I also have not really figured out yet which chemicals are inside the displays themselves, seems like there are many possibilities.
It is always possible to ask the supplier, but I don’t think they will tell me much since it is probably IP.

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If this has already been properly addressed, I apologise, as I have not yet read the entire thread, however, regarding temperature, this article on the national library of medicine website, indicates that “Studies show that a temperature of 52 degrees C (125 degrees F) can cause a full-thickness skin burn in 2 minutes and a temperature of 54 degrees C (130 degrees F) can result in a full-thickness skin burn in 30 seconds.”, so if the temperature is hot enough to damage the screen, you’ll need a hospital before the screen gets damaged.

As for saunas, it’s much the same way that if you’re in an ice bath that the water around you is actually kept at a safer temperature if you’re not moving, or only moving very little, because your body regulates by (in the case of the sauna) producing a layer of sweat on you to protect the skin, hot tubs aren’t normally kept hotter than 40C, or 120F, and (in the case of ice baths), it heats a very thin amount of the water around your body, that’s against your skin, as a barrier between you and the colder water, and also by increasing how much heat it’s producing to ensure it can maintain that layer of warmth. Both situations involve an increased heart rate.

Please note that the article I linked does specifically reference studies regarding children and burns, so adults may be capable of tolerating slightly hotter temperatures, but I can assure you that it is not much higher.

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Thank you for your input!
Temperature rise and decrease has been a topic of discussion for some time.
In this case the display (because it is even deeper than skin surface) should always be within safe operating bounds, that is good to know!

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I don’t know if this has been addressed yet, as I have not read the entirety of the thread yet, but if the display is reaching a temperature where the liquid inside of it can freeze, the skin above it will have also frozen solid, and if that happens, you’re either dead, or going to be soon, or going to lose the limb that was exposed for that long.

I have many piercings, and live where it’s below -30C for 4 months, sometimes longer, sometimes colder. We wear parkas, snow pants, mittens, toques, etc, because it’s not safe otherwise, so the implant would definitely be covered, unless someone was doing a polar bear swim, or something, but those don’t tend to last very long, certainly not long enough to cause the implant to go lower than -10C, or even close to that.

(Frost bite begins to set in at 0.55C, so the skin would likely be irreparably damaged if the limb got cold enough to damage the implant.)

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That’s a great source!

Those studies take an average person and a full exposure to the heat, though. In which case, yes, that would cause serious damage to the skin…

But there are 2 items to take into consideration here:

  • 1: I was talking about edge cases.
    a cook can handle much higher temperatures than the average person referenced above. definitely able to handle higher than 52 degrees for short periods of time without damage to the skin.
    I do wash dishes with 70C water and have no damage from it, but that’s enough to blister someone “untempered”. Obviously I don’t keep my hands immersed in water at that temperature, otherwise I would be cooking myself :sweat_smile:.

  • 2: we need to consider the mediums.
    we’re talking about 2 minutes of constant exposure to damage skin.
    you might give it 2 hours under the same circumstance and there will be no damage done to steel or glass.
    but how long does it takes for the medium on those display’s e-ink to have their viscosity permanently affected?

Combining both factors, I remember once I got a splash of oil hitting my skin and an e-reader (years ago). I wiped the reader in less than 2 seconds and didn’t even bothered with my skin.
The reader had permanent blotches where the droplets landed on the screen and I had no damage to my skin whatsoever.

That makes me think… it doesn’t need to destroy de display. Just the slightest change in viscosity may be enough to render it useless.

Also, worth noting that I don’t know the answer to this because I don’t know the exact values where each e-ink has been tested (or not).
I just think this is something worth testing before implanting it on someone that might be within any of these edge cases.

That is a potentially misleading statement.
Even though it’s correct, it’s not always correct… ie:

I can intentionally hold a display under 0C water with my bare hands for long enough for it to be permanently damaged while my hand is still fine.

Remember, the display does not need to get frozen/destroyed. just a slight change in the fluid’s viscosity is enough to damage it.

But again, everything seems to point that you’ll need an extreme edge case for it to be damaged.
So I do think @hugovantriet 's implant will suit their use case just fine.

But this is an open forum, so I do care about avoiding potentially misleading conclusions.

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Maybe, maybe not, but if they have it patented, you can look up the patent number, and see what’s in it anyway.

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clever

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Yeah, I was gonna say, steak and veal get cooked to at least 65C, so people would cook at that temp too. I know when I was washing dishes at a restaurant, the required water temp was 81C for anything that wasn’t going to be washed with chemicals, so I had to wear thick gloves to do dishes (both b/c of the temp and the quaternary ammonium compound used for cleaning).

Well, the article says 2 minutes for a full thickness burn, or as they used to call it, a third degree burn. Lesser burns will occur in much less time than that, and I do agree that one can become tempered to exposure over the course of time. So an acclimated person’s body would also be able to protect what’s under, or in the skin much better than a person who is not acclimated, but they’re not just developing tougher skin, though callouses certainly would help, but that’s dead skin. Live skin would be developing better ways of dispersing the heat to regulate the temperature, and protect itself so it doesn’t cook. So I think the implant would be safe in either person, just that the acclimated person would be able to handle exposure for longer times, and thus so too should their implant.

I still don’t think the implant is going to reach a hotter temperature than the skin and meat surrounding it, until after that skin has increased to much hotter than the skin should be able to handle. I suppose one way of doing a test would be to expose yourself to those temperatures that you’d normally expose yourself to, in those areas, and then do a combination of an implanted xBT for internal temperature read, and a temperature sensor like the health inspectors use to see the surface temperature (like the point and click ones. Though I don’t think the results would be different from what I’m saying, and what the medical studies show, but it would be interesting all the same.

As for how it would effect the screen, it would depend on if there was a drastic change in temperature, and if there was, then the only way to know if it’s going to damage the screen would be to actually implant one, and see what happens. I don’t think any sort of external temperature tests would be equivocal because dead meat doesn’t transfer heat how live meat does, which is unfortunate for testing.

The testing another user did with being in a sauna with their xBT also evidences that the temperature change for someone in that environment is, internally, minimal.

If it was from a deep fryer, the oil is kept at around 163C, and the screen cover for the e reader are plastic, so they melt easy, and don’t have anything implemented in them to regulate that level of temperature. Your skin’s reaction being able to disperse heat that quickly to protect you should be proof enough that your skin would need to be severely damaged before anything beneath it would ever be damaged from temperature.

Definitely not a misleading statement. There’s an extreme difference between you holding a display in your bare hand, and a display being implanted under your skin in that same hand. There’s an even bigger difference when you move that display further up the arm, for the same reason your body is more capable of warming your arms than it is of warming your hands, because they’re closer to the body’s core where it produces heat (same reason why when you warm a person up, it’s faster if you put heat packs under their arms than it is if you put them in/on their hands). And since we’re talking about implants, and not about things people are holding outside, it makes no sense to reference data for something outside of the body. Your hand is incapable of forming a perfect seal, whereas your skin is perfectly sealed unless it’s damaged.

The display is capable of operating at -10C, and the inside of your skin is never going to reach that temperature unless you’re dead, being tortured, or doing something that will likely result in loss of limb due to frost burn. If the temperature of the display when it’s under the skin, has reached below -10C, or even to -10C, the water in your skin is going to be crystalised, which means it’s dead, blood is not flowing through it, and it’s not going to be possible to save that tissue, and that’s going to happen long before your skin reaches -10C.

If the display when implanted, were to reach -10C before the skin did, then you’d have a lot of people with frozen meat under their skin, needing hospital help where I live, but that’s not how skin works. I can appreciate your interest in avoiding misleading conclusions, but that’s not what I provided. The confusion you’ve encountered is because you’re conflating things you’ve done with things outside the body, as being equal to what would happen to something inside of the body.

As an aside, I hope what I’ve said hasn’t come across as rude, as that’s not my intention, however I am aware that I tend to say things in a manner that comes off as such. Anyway, what I mean to say is that what I’ve said is, face value, no hidden meaning, no tone, no subtext, no interpretation. Anyway, I suck at conversation, so I’m gonna stop.

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Hello again,

The last few months were unfortunately very busy for me.
I got a new job (as a R&D employee), I had to finished the last projects for my studies and I went on a family vacation.
Unfortunately I did not have much time to continue with this project, but today I’m happy to say that I am back at it!
I just ordered the custom development board I showed here before, and now I am waiting for it to arrive (It will probably take around 2 weeks).
Since I have a new job and I don’t work in the food industry any more, I think it is time to get my first xSIID implant.
When I order my stuff from here I will also get the NTAG I2C test card to start developing with the NFC part as well.

I am happy to be back and sorry for ghosting this thread for so long without saying anything.

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Congrats on the new job!!

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I got mail! Time to get to work…
IMG20230911170842

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While writing the SPI driver for the memory IC, I unfortunately found out about an issue I need to fix in order for this to work.
The microcontroller I had in mind for moving data from memory to the display has only 1 SPI controller port.
Normally, this isn’t a big deal, we just need another ‘chip select’ signal to switch between the 2 devices.
The issue is, if you deselect a device, it will drop all the data that has been written to it and not confirmed.
I would normally copy the image into RAM memory and then write it in one go to the display, but I only have 2KB to work with.
This means I need to find a new microcontroller with more RAM, or with dual SPI ports so it can keep 2 connections active at once.
The current microcontroller was chosen for its tiny size, but it seems like I am forced to look for a bigger one, while trying to keep the package size as small as possible.
I will go back to the drawing board, and I will inform you if I have any updates.

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That’s unfortunate, this looks like a really interesting project. Are you assembling the boards or having the PCB mfg do it?

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Currently the prototype mostly lives on a breadboard.
I had the devboards I ordered also pre-assembled for my convenience.
When this gets into production (if at all), I will have it pre-assembled on a flex PCB.
Mostly because I am unable to solder such microscopic parts myself.
I will also need someone else from this forum who is more qualified to finish the production by sterilizing everything and sealing it in biocompatible materials.

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During the past days I did some research on replacement chips.
Sadly, there are none matching the form factor of the old one with more functionalities (as far as I know, suggestions are welcome).
I think that for now I need to focus on using passthrough mode on the NXP NTAG I2C chip.
This would result in having to reflash every time you want to change the image (not sure how much of a dealbraker this would be).
For now, my first priority is getting my hands on the NXP NTAG I2C for testing.

UX design question for you guys: would you mind having to reflash the image from your phone every time instead of just clicking a memory button?

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