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.