Display Technology Researchers Make Representations Tangible

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Researchers at UC Santa Barbara have developed an innovative haptic display technology: The screens are equipped with tiny pixels that expand outward when illuminated. This allows animations to be displayed that can both be seen and felt.

This technology could one day enable high-resolution visual-haptic touchscreens for automobiles, mobile computers, or intelligent architectural walls. It was developed at the RE Touch Lab of UC Santa Barbara, and the results were recently published in the journal Science Robotics.

How Does the Tactile Display Work?

• The core of the technology involves thin display surfaces integrated with arrays of millimeter-sized (a few hundredths of an inch) optotactile pixels.
• The pixels are individually controlled by projected light from a low-power laser, a form of optical addressing.
• The same light source powers the pixels, which contain an air-filled cavity and a suspended thin graphite film.
• The film absorbs the incoming light and quickly heats up, which in turn warms the trapped air.
• The air expands, causing the top of the pixel to bulge outward by up to a millimeter (0.04 inches)—creating a slightly perceptible elevation over the illuminated pixel.

High Speed Enables Dynamic Representation

The process is so fast that by sequentially scanning many pixels with a beam of light, dynamic graphics—contours, moving shapes, characters—are created, which can be both seen and felt. The refresh rate is high enough to continuously display animations, just like conventional video displays.

Since the light is responsible for both illumination and power supply, no embedded wires or electronic components are required in the display surfaces. Instead, a small laser scans the surface at high speed, illuminating each pixel for a fraction of a second.

The technology is also scalable: The team has presented devices with more than 1,500 independently addressable pixels.

System Can Generate A Variety of Tactile Content

The researchers also examined what users perceived when interacting with the displays. By touch, participants in their study could pinpoint the position of individual illuminated pixels with millimeter accuracy, accurately perceive moving graphics, and easily distinguish spatial and temporal patterns. The researchers emphasize that these results indicate the system is capable of generating a wide variety of tactile content.

The Idea Has Been Pursued Since the 19th Century

The researchers point out that the idea of converting light into mechanical motion has remarkable precursors: In the 19th century, Alexander Graham Bell and others used focused sunlight, modulated by the blades of a rotating fan, to produce sound in air-filled test tubes.

These visual-tactile displays could be applied in many areas:

• For the production of touchscreens for cars that mimic physical controls,
• for e-books with tangible illustrations that come to life on the page, or
• for mixed reality surfaces that bridge the gap between the digital and physical world.

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