Over the next several years, Israr and his colleagues traveled the world, presenting the model at technology conferences to build interest. While the technology impressed scientists and businessmen, they kept asking what else it could do. Creating textures on a screen was interesting, but could it display 3-D graphics or convey different sensations to different parts of a hand, truly mimicking the way we experience touch in our day-to-day lives? Israr decided to find out.
Reaching New Peaks
As he read up on the sense of touch, Israr learned that humans perceive dips and slopes on a surface primarily through the stretching of the skin. In places where a surface is raised, they experience increased friction on their finger. The opposite naturally occurs with a dip in the surface. Israr then surmised that a higher voltage, which would create more friction, would give the user the impression that the screen was pushing up against his finger, producing a 3-D effect. With that hypothesis, he went to work trying to create the perception of a single large bump on a flat screen.
Israr again turned to research subjects, asking them to feel a touch screen powered with varying voltages. Israr projected an image that looked like a bell photographed from above and asked test subjects what type of frictional pattern best matched the feeling they’d expect when they slid a finger over it. He tried turning the voltage off when users reached the top of the bump as well as matching the voltage to their perceived height of various parts of the image.
But neither effort felt right to users; the second one made most of them feel like the surface was raised but then plateaued. In the end, the pattern of electrovibration that felt to users most like the picture matched the frictional forces to the slope of the bump: the steeper the curve, the more voltage required to increase the friction.
While several other researchers could also create textures on tablet-size devices using vibration, Israr was the first to develop an algorithm for tactile rendering of 3-D features and textures on touch surfaces. Using the same theory he used to create his raised surface, Israr wrote an algorithm that allowed users to feel any “depth map,” a computer graphic that conveys information about the distance and surface of the object depicted. It was a breakthrough for Israr and his team.
Israr thinks the next step will involve seeing if the device can provide different sensations to each finger of a user. This would allow for another level of 3-D tactile illusions: Each finger of a hand gliding across a desk would reach the corner in succession; a piano keyboard app would allow users to feel a dip in several keys while playing a chord.
“The possibilities are huge if we could transmit signals to multiple fingers,” Israr says. “Imagine what this could be used for. We could have the potential to create 3-D interfaces for the blind. We could feel clothing before we bought it online. We could transmit touch when talking on Skype.”
The potential application for a haptic screen is perhaps best shown through one of Israr’s favorite illusions on the TeslaTouch. In his office, as Quintanilla handles the tablet, he comes upon an image of a rectangle on a grid, like something out of middle-school geometry homework. Israr guides Quintanilla’s finger to the corner of the rectangle and asks him to drag it.