Printing Transistors in RFID Tags

Radio-frequency identification (RFID) tags have made paying toll fees and public transit fares a breeze. But the tags, which are made of silicon, are still too expensive to replace ubiquitous barcodes to similarly speed up grocery store checkout lines by remotely scanning a product while it's still in the basket.

Cheap plastic RFID tags could soon change that. Researchers in Sunchon, South Korea, have printed RFID circuits on plastic films using a combination of industrial methods: roll-to-roll printing, ink-jet printing, and silicone rubber-stamping. They use inks containing various materials--silver, carbon nanotubes, and a nanoparticle-polymer hybrid--to deposit the circuit's components, such as capacitors and transistors, layer by layer.

Gyoujin Cho, a professor of printed electronics engineering at Sunchon National University, who led the work, estimates that the tags cost three cents apiece. To replace barcodes, RFID tags will need to cost a penny or less. But Cho says this should be achievable if all the layers on a tag can be deposited with a roll-to-roll process.…