Because the system is pressurized, the pressure information can itself be used as an input, Harrison says. For example, if the screen were used to control an MP3 player, a person could press a button harder to scan through radio stations or songs faster. While many touch-screen displays can also register different levels of pressure, the glass or rigid plastic used doesn't provide any tactile feedback.

Rob Miller, a professor of electrical engineering and computer science at MIT, says that this type of interface is particularly likely to find its way into car dashboards. "When you're driving a car, you're situationally impaired," he says. "Your eyes need to be on the road, not hunting for the right button and watching whether you pressed it right."

In a small user study involving the Carnegie Mellon display, testers found the pneumatic buttons as easy to use as static ones while taking a simulated driving test. They also glanced at the pneumatic buttons only as often as they glanced at the physical buttons.

Due to its pneumatic nature, the system is currently fairly large, but Harrison says that he is trying to find ways to shrink it. "You can't get a pump inside a cell phone," he says, "but one possibility is to have a balloon and squeeze it using a conventional motor."