At the heart of the technology are thin display surfaces that integrate arrays of millimeter‑sized optotactile pixels. The pixels are individually controlled by projected light from the low-power laser, a form of optical addressing. The same light source powers the pixels, which contains an air‑filled cavity and a suspended thin graphite film. The film absorbs incoming light, and rapidly rises in temperature which, in turn, heats the captive air. The air expands, and the pixel’s top surface deflects outward by as much as one millimeter — yielding an easily perceptible bump above the illuminated pixel.
The process is so fast that scanning a light beam across many pixels in succession yields dynamic graphics — contours, moving shapes, characters — that can be both seen and felt. The refresh rate is fast enough to enable animations to look and feel continuous, as with familiar video displays.
Because light provides both illumination and power delivery, the display surfaces require no embedded wiring or electronics. Instead, a small scanning laser sweeps the surface at high speed, illuminating each pixel for a fraction of a second.
The technology is also scalable: the team has demonstrated devices with more than 1,500 independently addressable pixels — significantly more than comparable tactile displays reported to date, Linnander said. Far larger formats are possible, he added, including displays that leverage modern laser video projectors.
The researchers also studied what users perceived when interacting with the displays. Using touch, participants in their study were able to accurately report the location of individually illuminated pixels with millimeter precision, could accurately perceive moving graphics, and were easily able to discriminate spatial and temporal patterns. The researchers emphasize that these findings indicate the system is able to produce a wide variety of tactile content.
While the team’s findings stand out among prior display technologies, Visell noted that the idea of turning light into mechanical action has noteworthy antecedents. In the 19th century, Alexander Graham Bell and others used focused sunlight, modulated by the blades of a rotating fan, to excite sound in air-filled test tubes. The same physical principles underlie the optotactile pixels have now been applied to a digital display technology.
These visual‑tactile displays could find uses across many domains. Visell envisions that the technology could be used to create automotive touchscreens that emulate physical controls, electronic books with tangible illustrations that come to life on the page, and architectural surfaces for mixed reality, bridging the digital and physical worlds.
Whatever the future may hold, the technology his team has invented embodies a simple, intriguing idea: anything you see, you can also feel.
