Touch Screens that Touch Back

Forget putting your phone on vibrate. A novel “high-definition” touch-feedback display can give a touch screen the feel of a textured surface. The technology was developed for mobile devices by the San Jose CA-based company Immersion, and is a step toward mimicking the feel of physical buttons on flat screens.

Simple haptic interfaces have been used in cell phones for years, to create silent alerts or provide limited tactile feedback when an onscreen button has been pressed. But such interfaces typically rely on elliptical vibration motors to create a shaking sensation, an approach that is slow and imprecise. Immersion believes this can be greatly improved by switching to a piezoelectric actuator.

Piezeoelectric materials produce mechanical stress in response to an applied voltage, or vice versa. They do this at great speed, which means piezoelectric actuators can respond quickly when a screen is being touched, says Steve Kingsley-Jones, Immersion’s director of product management.

A prototype device featuring the technology was demoed two weeks ago at the Mobile World Congress in Barcelona, Spain. When activated, a piezoelectric strip placed along one edge of a touch screen causes the screen to move from side to side, a slight movement that is felt by a finger touching the screen. A suspension system holds the screen in place, ensuring that the case does not move.

Traditional motors can oscillate at about once every 50 milliseconds, but the piezoelectric actuator lets the screen move back and forth 100 micrometers every millisecond. Kingsley-Jones says it is possible to run a finger over the screen and “feel” individual on-screen buttons. “You can actually feel the edges,” he says.

Better haptics could make touch screens easier to navigate, and reduce the need to look at the screen, says Vincent Hayward, a professor at the University of Pierre and Marie Curie in Paris, and a leading expert in the field. Hayward, who cofounded a company called Haptec that was later acquired by Immersion, says it is possible to use vibrations to trick a person into feeling all manner of sensations. “You have the uncanny experience that the flat surface has relief,” he says. “The glass can become tangible.”

Immersion is experimenting with making the digit at the center of the virtual dial pad feel as if it stands out more than the other keys. This would make it easier for the user to feel where the other keys are, says Kingsley-Jones.

What’s most interesting about Immersion’s approach, according to Hayward, is the lateral movement of the screen. Because it’s difficult for nerves to distinguish the direction of such movement, it’s possible to trick the senses into feeling upward pressure where there is none, he says.

Immersion is also developing software to record the feel of a real button and replicate that on-screen. In blind tests, subjects were unable to distinguish between pressing a real button and a simulated one, says Kingsley-Jones.

Immersion is talking to handset manufacturers and expects the first devices incorporating the technology to appear toward the end of the year.