Electro-wetting display (EWD) is based on controlling the shape of a confined water/oil interface by an applied voltage. With no voltage applied, the (colored) oil forms a flat film between the water and a hydrophobic (water-repellent) insulating coating of an electrode, resulting in a colored pixel.
When a voltage is applied between the electrode and the
water, the interfacial tension between the water and the coating changes. As a
result, the stacked state is no longer stable, causing the water to move the
oil aside.
This makes a partly transparent pixel, or, if a reflective
white surface is under the switchable element, a white pixel. Because of the
small pixel size, the user only experiences the average reflection, which
provides a high-brightness, high-contrast switchable element.
Displays based on electro-wetting provide several attractive
features. The switching between white and colored reflection is fast enough to
display video content.