US Patent 7548363 Bi-stable electrowetting optical element and driving method therefor

An optical element used, e.g., in an electrowetting display device having a number of pixels, is arranged in an array. Each optical element includes a cell filled with a polar conductive fluid, such as a water solution, and a non-polar fluid, such as an oil. The cell further includes first and second planar electrodes covered with first and second hydrophobic layers. By applying a voltage between the first fluid and alternately the first or second electrodes, the oil is forced to migrate between the first and second hydrophobic layers. Thus a bi-stable, energy efficient optical element is provided.