Using thin LEDs and polymer notes it would be possible to develop a layered wafer note that stores enough charge, from solar or ambient light collection, to activate RFID scanners This would allow banknotes that can be accessed electronically by retailers, allowing them to transmit advertisements to the face of the notes, as you pass within close proximity of their premises.

Advertising revenue defrays the cost of development, subsidising it while driving the public awareness campaign with their constant presence on your money.

Admittedly, this is far more likely to occur first with credit/debit cards than it is with cash. Cards tend to have a greater intrinsic value, and are already being loaded with solid state storage devices.

"Special, today only. Jamaican Coffee and Donut, just $2"