In one hint of the future, Apple Inc. has been issued a series of U.S. patents including No. 8,378,797 for a “Method and apparatus for localization of haptic feedback.”
This system would allow for the localized delivery of a vibration to one point on a touch screen in order to produce a more natural sensation of typing. But this crude vibration cue is only the first step. There are an entire series of technologies under development that can render synthetic touch with increasing fidelity. Local shape and texture can be displayed using an array of pins activated by electrical signals that move up-and-down or side-to-side. These tiny movements can be achieved using various present-day actuator technologies including shape memory alloys, pneumatic devices, microelectromechanical systems (MEMS) and piezoelectric elements. Crucially, these actuator devices are very fast allowing them to respond dynamically to the user’s exploration. Depending upon the application, these mobile pins can be covered with a thin elastic membrane to create a smoother contact with the skin. The arrays of dynamically-controlled pins that form a touch display can either lie on a flat surface, like a present day touchscreen, allowing for tactile exploration by the user or they can be embedded into a roller mechanism and scanned over the fingertip. Yet another touch display under development, which may be able top impart even more subtle sensations, uses an array of tiny surface electrodes to pass miniscule electrical currents into the skin and thereby activate nerve endings artificially.