Antenna-less RFID tags designed to work where others don't – on metal objects
Radio frequency identification (RFID) tags are definitely a handy way of tracking shipments. Instead of simply crossing their fingers and hoping for the best, importers and exporters can check the location and condition of shipped items in real time, by remotely accessing the data being transmitted by RFID tags attached to those items. Unfortunately, many such tags don't work on metal objects such as shipping containers or oil drums, as the metal interferes with the functioning of the tags' antennas. A new tag developed at North Dakota State University gets around that limitation, however - it uses the metal object as its antenna.
Typically, when an RFID tag is to be attached to metal cargo, the antenna is placed on a spacer to keep its electromagnetic field from being affected by the metal. This results in the tags having a total thickness between 0.5 and 3 centimeters (0.2 to 1.18 inches), depending on the type of tag being used. In a rough-and-tumble shipping environment, such protruding tags can be damaged or ripped off.
The North Dakota tags, however, are less than 3 millimeters thick, and are applied directly to the metal - they could even be recessed into it. This thinness is due partly to the fact that they have no antenna of their own, but also because of a unique material used in their construction. This material is highly electrically permeable, allowing the tags' integrated circuits to receive current from the metal upon which they're mounted.
The university is currently looking for corporate partners interested in licensing the technology.
Source: North Dakota State University