From Smalley's Research Watch Blog:

"All plastic radio ID tags

One of the promises -- and perils -- of radio frequency identification (RFID) tags is that when the chips can be made cheaply enough, anyone, including manufacturers and governments will be able to tag, and therefore track, everything under the sun.

Key to making them cheaply is making them entirely of plastic. A high-speed organic diode could be the last piece of the puzzle.

RFID tags don't require a power source. They are activated when a tag reader hits them with radiowaves; the radiowaves provide the power the tags need to transmit a signal back to the reader. Plastic transistors are fast enough to carry out the task of transmitting a tag's ID codes, but the rectifier, which converts alternating current produced by the reader's radio signal to the direct current needed by the tag's circuits, is another matter. The researchers' organic diode rectifier -- at 50 megahertz -- is fast enough to do so. (50 MHz rectifier based on an organic diode, Nature Materials, August, 2005)"

The above quote is from the August 15, 2005 posting on the Smalley's Research Watch Blog. I have reproduced the entire post, something I normally do not do, because the blog does not offer individual permalinks by date. It is a fascinating blog covering a wide variety of technology and science topics and I urge you to click through and check it out.

By the way, Smalley's is seeking reader contributions in order to be able to continue publishing its Technology Research News. It seems like a worthwhile publication and I hope they find the necessary funding.