FLEXIBLE ELECTRONICS
Thin flexible tags capacitively
transfer their data to touch screens
By IJulien Happich n cooperation with card and board games global manufacturer Cartamundi, nanoelectronics
research centres imec and TNO have developed a flexible capacitive
identification tag that can communicate with capacitive touch screens.
The C-touch tags described in a Nature Electronics paper “Touchscreen tags
based on thin-film electronics for the Internet of Everything” consist in flexible chips
built around thin-film transistors that can be easily integrated in paper and plastic
products such as tickets, certified documents, payment cards, or playing cards as the
demonstrator shows.
Each tag encodes a unique identifier
which can be capacitively read out
by a smartphone app via any capacitive
touchscreen, turning whatever object it
conforms to into a smart product whose
identifier can then be matched in a database
online to trigger a specific action.
The 12-bit thin-film capacitive identification
tags are powered by a thin-film battery
or even better, a thin-film photovoltaic cell that converts light from the touchscreen,
powering the mere 38nW required to support data transfer rates up to 36bps (at a
0.6V supply voltage).
Smart cards or other objects with embedded C-touch tags could securely interact
with the 4.5 billion mobile phones used worldwide, as well as with the large number
of touch screens now being integrated in cars, booths, walls, coffee machines and all
sorts of everyday objects.
These tags offer security thanks to the
very short communication range; general
compatibility thanks to the presence
of capacitive touchscreens everywhere;
and the potential to be produced at low
cost thanks to the 0.8cm2 monolithically
integrated antenna. Compared to existing
RFID technologies such as NFC, the new
C-touch tag does not require an external
antenna, making the tag much smaller compared to current NFC tags. The C-touch
tags could become an alternative in all those use cases where interaction via touchscreens
is feasible, but RFID/NFC tags are either too large or too expensive or where
contactless reading is a disadvantage.
For example, in board games where cost is a discriminator, to provide higher security
in payment cards, or to replace difficult to service and manage hardware readers
and access control points with easy to service and update apps on standard mobile
devices, etc.
“Our C-touch tag paves the way to a multitude of new applications compared to
standard RFID or NFC solutions as it takes advantage of the widespread availability
of touchscreen readers compared to the limited amount of NFC readers,” says Kris
Myny, principal scientist and R&D team leader at imec. “We are testing the tag system
and communication method using a range of different touchscreens from a variety of
brands, including Apple, Samsung and Huawei.”
“Our next steps will be to further improve the performance of the tags, enable new
features such as bi-directional communication with touchscreens, and work with
companies in developing solutions based on C-touch tags in different application domains”,
explains Prashant Agrawal, program manager for thin film electronics at imec.
Although for this demonstration, the researchers have used 12-bits codes programmed
during fabrication, such tags would not be limited to 12-bit, as kbit memories
have already been demonstrated in flexible thin-film electronics. What’s more, the
technology could be developed to make re-writable tags.
“The C-touch tags will enable us to even further blur the boundaries between
digital and physical gaming and unlocks exciting new consumer experiences”, commented
Cartamundi’s CTO, Steven Nietvelt involved in the project.
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