alt Hacker News> How close are we to smart dust I wonder? How small can we make wireless communications?
There's two limiting factors for 'smart dust': power (batteries are the majority weight and volume of this vape), and antennae (minimum size determined by wavelength of carrier wave).
I believe you can fit an NFC module in a 5x5mm package, but that does externalize the power supply.
RFID tags are powered wirelessly, one could imagine powering smaller particles when operating on higher frequencies (RFID is on 13.something MHz requiring relatively large coils). A directional antenna could send a pulsed beam to power a subset of the particles in the area and afterwards receive their signals.