Introducing a screen-printed, flexible antenna for RFID devices

By Gary Elinoff, contributing writer

A partnership including Quad Industries, Agfa, IMEC, and TNO has developed an RFID tag and readout system based entirely on screen-printed circuitry. Notably, the readout unit’s antenna is also screen-printed, allowing the device as a whole to be melded to any type of surface regardless of its geometry, allowing users tremendous flexibility in deployment.

A flexible antenna for the interrogator, too

While screen-printed antennas have already been successfully utilized in RFID tags, successfully deploying this technology into the interrogator, or reader as IMEC describes it, has proved challenging. Because of the poor Q-factor inherent in previous printed antennas, manufacturers have heretofore been forced to rely on more rigid reader antennas. The antenna demonstrated in this system was screen-printed by Quad Industries, utilizing printing inks developed by Agfa.

Flexible screen-printed antenna. Source: IMEC.    

This system is a demonstration project, a demonstrator not intended, at least at this point, to be a commercially available product. The application showcased here was specifically targeted for badge security. Other potential applications for this technology include smart packaging, wearables, gaming and the Internet of Things (IoT).

The access badge, or tag, includes a 12-bit RFID tag and exploits IMEC’s metal-oxide thin-film transistor (TFT) technology. Composed of 438 TFTs and utilizing a bendable plastic substrate, it is flexible as is the credit-card-sized antenna.

In security applications, it is, at times, necessary for an individual to be able to verify herself, even if she doesn’t have the necessary identity badge on her person. To this purpose, the reader includes a touchscreen interface with a numerical keypad, allowing the user to verify her identity by entering the proper sequence of numbers. As is everything else in this demonstrator, this subsystem, too, is screen-printed and, as such, is also flexible.

Nanoparticles are the key

Previous screen-printed antennas have suffered from not only from poor Q-factors, but also from high electrical resistance, making them inappropriate for use in RFID readouts. This required the use of antennas based on more rigid technologies, precluding reader flexibility. Silver (Ag) inks based on nanoparticles produce structures that can alleviate both issues, making flexible antennas with much wider applicability.

It is expected that the combination of the flexible antennas made possible by the new nanotech silver inks, combined with flexible TFT transistors, will have many new applications in which physical flexibility and low manufacturing costs are paramount.