Or would they be invisible?
There are no implantable RFID tags made of conductive polymers. Conductive polymers are used on some ultrahigh-frequency (UHF) antennas, but implantable transponders are passive low-frequency (LF) devices, which require a coiled metal antenna.
—Mark Roberti, Founder and Editor, RFID Journal
Are There Any Wireless RFID Antennas on the Market? »