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I am curious why implantable RFID capsules are made of glass because they create a huge risk of breaking under the skin causing some serious trouble.

I would guess a silver/titanium encasing will be better, and, if I'm not wrong, those metals are not magnetic, so I don't see them causing a problem with the electo-magnetic fields.

I'll put the same question on a medical stack exchange, and see maybe the reason is medical not electronics related.

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    \$\begingroup\$ A capsule made of conductive material will not allow the RF signal to pass through, as it will act as a Faraday Cage, making the device pointless. Magnetic properties alone do not determine radio signal propagation. \$\endgroup\$ – Anindo Ghosh May 29 '13 at 10:33
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Glass is chosen because of it's chemical composition. Certain glass formulations are very close to the composition of bone, making it very biocompatable, and the composition can be tweaked for various behaviour (mostly regarding the way nearby tissue reacts).

Furthermore, you are far, far overestimating the issue of the capsule breaking. Any trauma sufficent to break the capsule will cause massive trauma, break or pulverize bones, and probably be a far greater issue. Basically, capsule failure of the glass tags is a non-issue from a medical standard.
A quick perusal of pub-med seems to support this, though it wasn't exhaustive. There is one interesting article looking at the survivability of RFID tags under extreme temperatures (such as autoclaving or liquid nitrogen), and only had one tag fail (and it didn't rupture or anything, it just stopped responding)after the tenth autoclaving cycle.

Basically, despite the fact that it's glass, implantable RFID tags are ridiculously durable, and far stronger then the puny human and/or pet they're normally implanted into.

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  • \$\begingroup\$ Thank you for your detailed answer. My train of though was that if there are those screws that they put in place to hold broken bones, then there is no reason why the capsule is not made from the same material. \$\endgroup\$ – Nicu Surdu May 29 '13 at 11:21
  • \$\begingroup\$ @NicolaeSurdu - Glass can be easier to work with. It's also a lot more bio-compatable. They use metal screws in bones and joints because they need the strength. \$\endgroup\$ – Connor Wolf May 30 '13 at 3:48
  • \$\begingroup\$ @NicolaeSurdu: Titanium is used in implants which are supposed to fuse with bone. If one were deliberately fastening an RFID implant to a particular place on a bone, making it out of titanium could help it stay in place. On the other hand, unless the implant was firmly held in its desired location until the body had fused it to the bone, it could end up moving and getting fused in a position which would interfere with the functioning of a joint. \$\endgroup\$ – supercat Jun 7 '13 at 15:29

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