Advanced Product Tags for Recycling Steven Saar Electrical Engineering, Princeton University Princeton, NJ 08544 USA ssaar@princeton.edu Valerie Thomas Princeton Environmental Inst., Princeton University Princeton, NJ 08544 USA vmthomas@princeton.edu Abstract Capacitive or inductive radio-frequency tags could be used to support the recycling of batteries and other prod- ucts. Both types of tags can be used on metal and non- metal products in some circumstances, although range and operability can be limited.. Keywords Recycling, RFID, tags. RADIO FREQUENCY TAGS Low-cost radio frequency tags are now available from a number of companies (Figure 1). Some have batteries that allow operation at long ranges, but for low cost and low maintenance, tags have been developed that do not have batteries (“passive” tags). Manufacturers envision that these tags could replace UPC bar codes and become the standard label for all products. Current prices for radio-frequency tags are about 25¢. In the longer term, new technologies, including fabrication of integrated circuits by direct printing, could reduce the cost of radio frequency tags considerably [1, 2]. Radio frequency tags are already used in a number of applications, including baggage tracking at airports, automatic highway tolling, and personnel identification. A typical radio frequency tagging system consists of a reader, a tag, and a data processing system. The reader has radio circuitry to communicate with a tag, a micro- processor, a memory, and an antenna. Most passive ra- dio frequency tags are inductive; the tag antenna and the reader antenna are loops of conductive material. When the reader sends a signal to interrogate the tag, current in the reader antenna creates an alternating magnetic field, which in turn induces current in the tag antenna. The tag modulates this signal with the stored information, and returns the modulated signal back to the reader. Figure 1. RFID tags. Left: An inductive tag from Texas Instruments, showing the conductive loops around the tag. Center: A capacitive tag from Motorola showing the printed black antennas; the chip is underneath the black square in the middle. Right: An inductive tag from Microchip. All of the tags are flexible and about 5 cm on a side.