s applied between the coating and the water, the tension between the water and the coating changes. The tension change forces the water to move the oil aside, resulting in a partly transpar- ent pixel or, if a reflective white surface is used, a white pixel. Displays based on electrowetting have several important attributes. The switching between white and colored reflection is fast enough to display full- motion video content. Also, because electrowetting is a low-power and low- voltage technology, displays based on the technique can be made flat and thin and placed inside mobile devices with limited battery capacities. Additionally, electrowetting's reflectivity and contrast levels are better or equal to the output of other reflective display types. In fact, the technique's viewability is close to that of paper. Electrowetting allows the creation of displays that are four times brighter than reflective LCDs and twice as bright as other emerging display technolo- gies. The technique also provides a display in which a single subpixel is able to switch two different colors independently. This results in the availability of two-thirds of the display area to reflect light in any desired color. This ability THE CRITICAL LAST INCH-INPUT AND OUTPUT TECHNOLOGIES is achieved by building up a pixel with a stack of two independently control- lable colored oil films plus a color filter. The colors used are cyan, magenta, and yellow, a so-called subtractive system that's comparable to the principle used in ink-jet printing. Unlike LCDs, no polarizers are required, further enhancing the display's brightness. Electrowetting is particularly well suited for applications that require a high-brightness and contrast-rich reflective display. The technology could lead, for example, to mobile phones that fold as flat as a credit card and can be slipped into a wallet. Displays could also be literally pasted onto an automo- bile's dashboard. It's also conceivable that mobile phone and PDA displays might be woven into clothing, allowing 