So how is such sorcery even possible? The researchers realized that the sensation of feeling a bump on a surface largely came from the skin on a fingertip being pulled and stretched as it moved across the raised area. And it turns out that this same sensation can be artificially created on a perfectly flat surface using electrovibration to generate electrostatic forces that create friction against a moving finger.
The other half of this breakthrough is a custom algorithm developed by Disney's research team that generates these frictional forces on the fly, based on what's being displayed on screen. So a stack of DVD cases would feel like a series of bumps, where as a ball would feel more like a large gradually curved surface. The technique is basically fooling the brain into thinking its experiencing something it really isn't, but the results are apparently remarkably convincing.
And the applications for this technology go well past just a cute interactive picture book that kids can also touch. This could make typing or playing joystick-based games on a phone or tablet actually enjoyable, and it would most definitely revolutionize how those with visual impairments use mobile devices. More here.