I've played with some tech demos that used electrostatic stiction (I may be remembering the name wrong) to create friction on a glass touch panel. The high vol

I've played with some tech demos that used electrostatic stiction (I may be remembering the name wrong) to create friction on a glass touch panel. The high voltage needed makes it a no go for most/all portable devices. I played with some other "cl controllable friction" tech but don't remember the basis of it. Iirc one actually made small indentations in the screen to simulate buttons. Had a bunch of limitations, I think the button placement was baked in at time of manufacturing, but it's been awhile and I don't trust my memory on the topic.