Transforming touchscreens into tag readers

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Imec has teamed up with TNO and Turnhout-based physical and digital gaming specialist Cartamundi to develop a flexible capacitive identification tag. The tags are thin flexible chips that can be integrated in a wide range of paper and plastic based objects, like tickets, payment cards, passports and board games, and are able to communicate with standard capacitive touch (C-touch) screens. These tags can then connect to the Internet simply by being placed on the screen or vice versa. The results, developed in the framework of Holst Centre, were published in this week’s Nature Electronics.

The new C-touch tag is based on thin-film transistor technology and is powered by a thin-film battery or a thin-film photovoltaic cell that converts light from the touchscreen. The 12-bit thin-film capacitive ID tag achieves up to 36 bit/s data transfer rates at 0.6 V supply voltage, which is compatible with commercially available touchscreen devices without requiring modifications. The flexible thin-film integrated circuit has a 0.8 cm2 on-chip monolithic antenna and dissipates only 38 nW of power at 600 mV supply voltage.

C-touch tags have a unique identifier that can communicate via any touchscreen and are very secure thanks to the very short communication range. Smart cards or other objects with embedded C-touch tags can securely interact with the 4.5 billion mobile phones used worldwide, as well as with the large number of touchscreens now being integrated in cars, coffee machines and all sorts of everyday objects – requiring no additional hardware, reconfigurations or additional costs for users.

Compared to existing RFID technologies such as NFC, the new C-touch tag doesn’t require an external antenna. The tiny antenna is part of the chip itself, making the tag much smaller than current NFC tags. The small size enables integration into everyday objects. Thus, C-touch tags are 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.

“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’re testing the tag system and communication method using a range of different touchscreens from a variety of brands, including Apple, Samsung and Huawei.”