Each cell can be turned off by bringing together the two layers using an electromechanical switch. (When there is little space between the layers, no visible light is amplified, making the cell appear black.) The switch moves after a pulse of voltage and stays in place until another pulse moves it back. As a result, the display is bi-stable, using little energy except to change the image.
By combining different sets of colored cells as subpixels, researchers can get any color of the spectrum, says Cathey. These MEMS devices are very robust, he says, and have been demonstrated to be reliable for more than 12 billion cycles.
“I personally think this technology is very cool,” says Arsenault. But because of the fabrication processes used to create MEMS devices, there is a constraint on how big such displays can be made, he says, which is the reason that Qualcomm is targeting small mobile displays.
What’s more, the energy savings will only apply when the display is used to view static, not video, images,
says Johan Feenstra, one of the founders of Liquavista, a spinout from Philips Research, based in Eindhoven, the Netherlands, which is also developing e-paper capable of video rates. “Bi-stability is only useful when you have an application where you don’t change the image often,” Feenstra says.
For video, this isn’t the case because the pixels have to be switched on and off almost continuously, says Guido Aelbers, chief operating officer at Polymer Vision, also in Eindhoven. “The moment you go to high speeds, you lose the low-power advantage,” he says.
Even so, both Aelbers and Feenstra believe that having video capabilities as well as color opens up a much bigger marketplace for e-paper displays. But with LCD technology constantly improving and costing less, it could well give the new display a run for its money, says Aelbers.