Flexible RFID Tags for a Smarter, Interconnected World

Flexible RFID Tags for a Smarter, Interconnected
World

By Kris Myny and Wim Christiaens

In a truly
interconnected world, microchips will not only be embedded in vehicles,
household appliances and health wearables, but also in cheaper consumer goods.
Smart labels – integrated into products’ packaging, for example – could be used
to track items from production till consumption, providing detailed information
on a product’s freshness, origin, or preparation instructions. By combining the
plastic RFID chips developed by imec and TNO in the frame of Holst Centre with
cost-efficient, screen-printed antennas, smart labels may soon become reality.
To explore this opportunity, imec has teamed up with Quad Industries and Agfa;
a collaboration that resulted in a security badge application that combines
plastic RFID tags with screen-printed antennas, both in the tags themselves and
in the reader.

Imec has been exploring
the domain of plastic electronics for more than a decade and launched the first
plastic microprocessor in 2012. And just last year, imec and Holst Centre
received the “Best Product” Award at the Printed Electronics Europe Conference
for a joint project with Cartamundi, a manufacturer of board games and playing
cards that specializes in giving regular games a digital edge. Together, they
developed a set of playing cards with integrated plastic RFID chips (with
regular, commercial antennas), combining the joy of a traditional card game
with the thrill of a computer game.

RFID (Radio Frequency
Identification)-chips allow close-range communication with a dedicated read-out
system. Traditional RFID chips are based on silicon CMOS technology, but imec’s
plastic chips use thin-film transistor (TFT) technologies instead. The
semiconductor, a thin film of metal-oxides (a blend of
indium-gallium-zinc-oxide) has a low temperature budget enabling direct
deposition on plastic foil, thus resulting in flexible chip technology.

This plastic technology
offers significant advantages. Kris Myny (principal member of technical staff –
imec) explains: “Because our plastic chips are ultrathin and flexible, they can
be invisibly integrated into virtually any product. You can wrap them around
your wrist, fold them, or bend them any way you want.” This flexibility makes
it possible to include electronics in products that could never be technologically
enhanced before. For instance, the plastic tags could be integrated in paper
packaging for food, in security documents or even in banknotes. Because the
tags are so thin, they can really disappear into the product’s design.

From a commercial point
of view, the main advantage of these thin-film microchips is cost-efficiency.
Kris Myny: “When introduced in large scale foundry manufacturing, plastic chips
have a unique cost advantage. This is because of the technological simplicity. Only
a limited number of steps are needed to produce these plastic circuits. When
mass produced, we see our chips evolving towards the cost of less than 1
eurocent. That’s about ten to hundred times cheaper than what you have on the
market today. Such an ambitious scaling plan would of course require a strong ‘application
pull’”, so we are working closely with application companies to define a vision
on how this new technology can grow.”

Quad Industries
specializes in printed electronics on different substrates, ranging from
plastic to textile or even paper. Wim Christiaens (R&D Director, Quad
Industries) explains: “The main advantages of printed electronics are that it’s
cost-competitive and allows for direct integration of electronics in any
material. Additive processing makes the production process faster and cheaper,
and offers a revolutionary path to make any object smart.”

Today, Quad Industries
still mainly makes use of silicon chips. Combining its technology with imec’s
plastic chips would not only reduce costs even further, but would also open up
new application opportunities because of the enhanced flexibility.

In 2015, a consortium
of Flemish companies coordinated by Agfa started a new SIM-SOPPOM[1]
project, i.e. Met@link. The project aims to use printed metallic inks for
conductive functionalities to enhance the technological and economic
feasibility of the Internet of Things and hybrid flexible electronics. The
project partners recently demonstrated an application example of such
technology, i.e. an access control system. The access badge contains one of
imec’s plastic RFID tags in combination with a screen-printed antenna.
Screen-printed antennas have been successfully implemented on top of RFID tags
before, but this time, the RFID reader also contains a screen-printed antenna.
Previously, the reader always used a standard printed circuit board (PCB)
antenna. Using a flexible screen-printed antenna instead allows optimal
integration of the reader, even on curved or 3D shaped surfaces.

The cooperation between
the Met@link partners was essential to make this demo possible and to overcome related
hurdles. A first issue that needed to be tackled was the energy-efficiency of
plastic chips: they are more power-hungry than regular silicon chips. Moreover,
printed antennas typically have a higher resistance and suffer from high energy
loss. Thus, the imec researchers first had to enhance the energy-efficiency of
their plastic chip. The energy-efficiency advances of such plastic chips have
been presented at ISSCC 2017, the flagship conference on circuit design, where
a power consumption of only 7.5mW was exhibited for a complete plastic NFC bar code
chip in contrast to an extrapolated power consumption of 250mW of previous
work. Agfa, in turn, developed a new kind of ink consisting of silver
nanoparticles. Because this advanced nanoparticle-based silver ink is a better
conductor, it became easier for Quad Industries to print antennas that can
function with imec’s plastic chip. All components then returned to Holst Centre
where the antennas and chips were assembled to create complete RFID tags. The result
is a flexible chip combined with a credit-card size antenna printed on plastic
foil that is so thin that it can disappear into almost any product.

The next step is to use
this combination of plastic RFID tag and a reader device with screen-printed antennas
to develop new, more advanced applications. On top, the new approach also makes
existing production processes more cost-efficient. Wim Christiaens “For Quad
Industries this is an important step forward to simplify our production
process. Using screen-printed antennas allows us to immediately print both our
customized touchscreens and the antennas on the same plastic substrate. This
way we can just print everything in one go.”

Cheaper technology
means more widespread technology. Smart supermarkets, for instance, might
become reality soon. Plastic RFID tags with screen-printed antennas could
bridge the gap between online and offline shopping. Online shops are able to
track consumers’ thinking process: they can see what you’ve bought in the past,
what you’ve clicked on and how many times, what you’ve moved to your virtual
shopping cart and then removed again. This is valuable information that
physical shops miss out on. A company like Quad Industries could, for instance,
develop a smart shelf with an integrated RFID reader. If you then use cheap and
flexible plastic RFID tags with screen-printed antennas in products’ packaging,
you can track how many times each product is picked up and put back. It also
makes it easier to monitor a shop’s stock or to check whether there are any
items past the expiry date. Because plastic electronics can be mass produced
via large-area manufacturing, this would hardly affect the products’ price. Thus,
plastic RFID tags could become retailers’ new bar codes.

At the moment, imec’s
plastic chips only contain a unique identifier that can be read by a custom
read-out system or a smartphone. The next step is to integrate sensors,
batteries, programmable memories and displays into these plastic tags. Once
these extra functionalities have been added, we can really start to imagine a
world where even every-day objects have become smart. For instance, one
possible application is the creation of smart blisters – with small plastic
RFID tags being integrated into pharmaceutical packaging. The chips could then
track whether or not you’ve taken your daily medication and could send
reminders to your smartphone if necessary. This kind of tag could also be used
to track individual products throughout the entire transportation process:
using sensors to monitor temperature and freshness. “The possibilities are
almost endless. Because plastic electronics are so much cheaper and can be
invisibly integrated into virtually any product, we can really let our
imagination run wild,” says Kris Myny.

To pave the way for
this Internet of Things, strategic partnerships between research and industry
partners are essential. Kris Myny: “Quad Industries can integrate our
technology in new, practical applications. They have the experience and
customer base to do this.” Wim Christaens adds: “As a technology provider, we
need to stay one step ahead of the market to provide innovative solutions to
our customers. That’s why the cooperation with imec is so important to us.
We’re both in Flanders, so working together is easy and we’re a good fit. The
advantage of a project like Met@link is also that we’ve become acquainted with
each other’s needs and possibilities. So we’re definitely interested in looking
into future collaboration opportunities with imec.”