Stuffing An RFID Card Into A Finger Ring

[Benjamin Blundell] loves wearable technology — but isn’t very happy with commercial offerings — at least not yet. He wanted to take one of his personal RFID cards, and fit it into a much smaller form factor, a 3D printed RFID ring.

The cool thing with most RFID cards today is they are made of a plastic that is quite easily dis-solvable in Acetone. Simply soak the card for about 30 minutes (depends on the card) and the plastic will simply peel away, revealing the microchip and copper antenna coil. It kind of looks alive when it’s melting…

The problem is, the antenna coil is generally the size of the card — how exactly are you going to fit that into a ring? [Benjamin] managed to find some surrogate RFID key tags, with a much smaller antenna coil. A little bit of solder later and he was able to attach his RFID microchip onto the new antenna! He mentions it is possible to wind your own antenna… but to get the frequency just right might be a bit challenging.

With his working RFID circuit complete, he quickly designed a ring in Blender and sent it off to Shapeways to be printed. It all fit together, and works perfectly!

This isn’t the first time we’ve seen a clever RFID transplant, [Becky Stern] transplanted a transit pass into her cellphone, and [Zach Charat] did too! What are you waiting for?

16 thoughts on “Stuffing An RFID Card Into A Finger Ring

  1. RFID can easily be embedded in smaller and the coil is not that important, look at the MOBIL “EZ-pass” RFID devices. when you take the keyfob apart it’s a small glass capsule. when I used it, I had my ezpass stuffed in a watch band. Use the right type of RFID to begin with and making a ring is not hard.

    What I wonder is why have we not seen “programmable” RFid’s yet? one that has no information on it and you could program it to duplicate an existing one? Take your RFID easy-tap credit card and clone it to a capsule so you can have it in a ring or watch band.

    1. The coil is definitely important but you’re correct that more compact RFID devices can by made by using cylindrical antennas. If you’d like to buy the capsules directly look up “PIT tags” which are widely used to mark wildlife and ID lost pets. Most of these are 134.2 kHz but you can find 13.56MHz versions if you look around.

      “Programmable” versions probably don’t exist commercially because they’d pose/expose a huge security risk, something that the companies making these aren’t exactly eager to do. That being said, it has been done:

  2. Hey guys, John McLear here from the NFC Ring project.

    We actually offer 20mm x 6mm ISO 14443 inlays you can put into a 3d printed ring and we provide STL files and tinkercad templates to design your own 3d printed ring.. They are the ideal form factor for a ring.

    If you don’t wanna purchase an inlay from us then you can actually get free 17mm x 12mm smartrac midas inlays as samples from Smartrac. Just use some of those social engineering skills you got on a sales rep and they will send you free samples ;) They aren’t the ideal form factor for a ring but they work great!

    We also provide the source code and spec sheets for all of our projects up on our organization page on github:

    Awesome to see more people hacking on this, keep up the great work guys! :)

    *Inserting semi-offensive plug to help grow our project.. PS you can pre-order an NFC Ring on

    1. If you wanted your project to grow you shouldn’t have mentioned Amal Graafstra on your kickstarter, We’re all crazy here, a little needle ain’t gon hurt too much.

        1. I jest, of course. I think it’s brilliant that you put the effort into the NFC ring, it really has changed how the average person is looking at NFC these days.

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