That's fascinating. Here's my best shot at an application: I have a mouse with a switch on the bottom, the switch lets me change the scroll wheel between free

That's fascinating. Here's my best shot at an application: I have a mouse with a switch on the bottom, the switch lets me change the scroll wheel between free spinning mode and clicky mode. I wonder if you could achieve a sort of soft-clicky-mode with three discs, printed with the right electret pattern and arranged so that the middle one is free-spinning. There would be preferred and not-preferred orientations, and you'd get a small force pushing the middle disc into a preferred location (providing tactile feedback). You could probably also embed some wires in the outer disc and use information about the currents induced to detect whether (and in which direction?) the wheel was spinning.