Electrowetting display
Originally developed by Philips Research Laboratories, electrowetting modifies the wetting properties of a hydrophobic (water repellent) surface using an electric field. Two immiscible liquids are sandwiched between a glass top layer and a reflecting electrode. The hydrophobic surface is on the lower electrode, and is covered with a layer of polar liquid and a layer of dark oil.
Fast switching
With no voltage across a cell, surface tension prevents the polar liquid from wetting the hydrophobic surface, which is covered by the dark oil and so reflects no light. A voltage greatly increases the wettability of the surface, and within 10 ms the polar liquid pushes away the oil to make the pixel reflect light.
The effect is capacitive and the currents involved are very small, so the mirror draws much lower power than conventional dimming mirror devices (less than10 mW versus more than 200 mW). Pixels are typically just 200µm across.
Fast switching
With no voltage across a cell, surface tension prevents the polar liquid from wetting the hydrophobic surface, which is covered by the dark oil and so reflects no light. A voltage greatly increases the wettability of the surface, and within 10 ms the polar liquid pushes away the oil to make the pixel reflect light.
The effect is capacitive and the currents involved are very small, so the mirror draws much lower power than conventional dimming mirror devices (less than10 mW versus more than 200 mW). Pixels are typically just 200µm across.