Intelligent Machines
Iridescent Displays
Qualcomm uses the mechanism that gives color to butterfly wings to make low-power, full-color e-reader displays.
Workers in Qualcomm’s factory in Hsinchu City, Taiwan, operate the same kind of equipment found in other display-making factories on the island, which are the source of more than a third of the LCD panels in new computers, tablets, and smart phones. Yet displays from this plant are like no others. They create color images by borrowing an optical trick at work in the iridescent wings of some butterflies. Each pixel in the new Mirasol display is made from microscopic structures that function like imperfect mirrors, reflecting back incoming light but altering its color. Full-color images can be created even in direct sunlight.
Since these displays use reflected light rather than emitting their own as conventional displays do, they consume far less energy than LCD displays. Yet unlike other low-power displays, such as the one in Amazon’s black-and-white Kindle e-reader, these render full-color images and can refresh quickly enough to show video.
The color isn’t yet as rich as that of a conventional LCD, but because the display consumes so much less energy, devices that use it can last longer between charges. “If you use one in a similar way to a Kindle, you should expect weeks of battery life,” says Clarence Chui, who leads Qualcomm’s Mirasol division. The technology could also lead to slimmer devices, since designers can use smaller batteries.
Qualcomm is starting with 5.3-inch displays for e-reader devices that are now on sale in South Korea and China. Later this year it will open a second, much larger Mirasol factory in Taiwan, which will have enough capacity to supply some of the world’s biggest mobile-device manufacturers. Chui says that the plant will be able to make Mirasol displays in sizes suited to a variety of devices, including smart phones and full-size tablets.
After this step, workers use typical photolithography tools to make individual pixels. The tools make tiny hollow structures that will act like imperfect mirrors.
When a person is looking at the display, incoming light is reflected in these structures in such a way that when the light finally bounces back out, its color is different; the color depends on the size of each structure. The photolithographic process also forms microscopic mechanical switches that turn pixels off. They close the structures, causing the reflected light to become ultraviolet and invisible and making the pixels appear black.
