In a paper presented at SID 2014, researchers from the Japanese touchscreen maker NLT Technologies disclosed how they were able to use a variant of electrovibration on a 4.1-inch-wide touchscreen prototype to create localized friction (at multiple touchpoints) and thus cause the perception of texture.
Based on what the researchers call a beat phenomenon of voltage waveforms, the company demonstrated regional electrostatic stimulation by using a matrix of transparent indium tin oxide (ITO) electrodes over the display's glass substrate, covered by an acrylic insulator layer.
By driving the X (horizontal) and Y (vertical) electrodes at varying frequencies around 1,000 Hz, the researchers were able to modulate the resulting electrostatic forces at the cross points, so as to obtain a localized stimulus in the excited regions and create different textures.
Electrostatic tactile display using beat phenomenon of voltage waveforms between electrodes.
When sliding your fingers across the display, this surface haptic effect reproduces skin sensations as if you were tracing actual objects on the display. With electrode pitches of 1.73 mm (X) and 1.75 mm (Y), the current prototype can emulate a given texture within an area covering multiple electrodes, roughly 4 x 4 mm2, to be felt correctly via skin sensation.
This multi-touch haptic effect can be synchronized with the actual image on the display, so that users can feel the texture they would expect from touching the real object.
In a press release, the company claimed that the technology could easily scale up for larger higher touch-density displays for applications ranging from texture sharing across the web to cockpit displays in autos and aircraft, and for devices aimed at the visually impaired, though Braille reading would require a finer resolution (discrete patches around 1 mm2).