The paper seems to say they use 200 kHz sinusoidal waves for the field. If that translates directly into what I see in an FCC table of frequency allocations, then that is in the AERONAUTICAL RADIONAVIGATION regulated by FCC Rule Part Aviation (87) [1]. They are driving the signal at 6 Vpp (peak-to-peak), at most 0.42 mA current with the lowest-resistance spray. I don't know how to even crudely calculate radio interference from those specs, so would appreciate someone giving guidance on where to look for a start.

What worries me about this approach is the need for calibration. I don't see anywhere that indicates they've tested to see the effects of the wearing down of the topcoat and conductive spray layer upon the accuracy. It would be cool to be able to simplify a light switch installation to slap(electrodes)-spray-spray-calibrate, it would suck if I had to re-calibrate once every few years.

Now if we can figure out how to beam low-voltage, low-amperage power over building distances and through insulation, then we could remove a lot of copper runs. Beam just enough low power to drive and sense these kinds of control surfaces, and control relays sitting in front of the actual devices' electrical connections.

[1] https://transition.fcc.gov/oet/spectrum/table/fcctable.pdf