[alted]

A WiFi/BT/NFC tag system has an antenna, and a radio circuit attached to the antenna.

It's almost possible to inkjet print circuitry with transistors in research applications; see [1]. 20 micrometer resolution is relatively easy, so a WiFi/BT or NFC antenna (~millimeter scale) is very possible. I agree, the tricky bit is making (a) enough transistors to for the radio at (b) sufficiently high frequencies. As in [1], inkjet-printed transistor circuits have at most ~10 transistors as of yet (and NFC chips, with > 512 bit memory, need at least hundreds if not thousands). According to [2], inkjet printed organic transistors are in the range of MHz frequencies; NFC (~13 MHz) may be possible; WiFi (~2.2 GHz) may not be for a while yet.

[1] https://news.ycombinator.com/item?id=24129506 [2] https://doi.org/10.1021/acsnano.6b06041