“Using an ‘articulating frame,’ the surface of such a device would create physical bumps or dots for the user to feel when it is in keyboard mode. Those surface features would retract and disappear when the device is not being used to type. It is detailed in an application entitled’Keystroke Tactility Arrangement on a Smooth Touch Surface,'” Hughes reports. “It is similar to an application first filed back in 2007.”
“‘The articulating frame may provide key edge ridges that define the boundaries of the key regions or may provide tactile feedback mechanisms within the key regions,’ the application reads. ‘The articulating frame may also be configured to cause concave depressions similar to mechanical key caps in the surface,'” Hughes reports.
Hughes reports, “The [possibility of a] tactile feedback keyboard [may have been] revealed as one anonymous source told The New York Times that users would be ‘surprised’ how they interact with the tablet.”
Full article, with more info and patent application illustrations, here.