US Patent 7724136 Revealable RFID devices

The antenna of a radio frequency identification (RFID) tag may be detuned by applying a conductive material in radio frequency (RF) contact with the antenna, such that the RFID tag is not operable. This material may later be removed, or the conductive effect of the material eliminated, thus re-tuning the antenna to its design specifications and restoring the RFID tag to an operable condition. In this manner, RFID tags may be manufactured in an inoperable state, to be subsequently made operable through the occurrence of an event, such as scraping off the conductive material.