Etulipa’s displays are based on its patented 2nd generation Electro Wetting Display technology. The first product based on this technology is a B/W 8 x 4-foot outdoor display that consumes less than 3 watt and runs ceaselessly on a solar panel and battery. Electronic-paper (e-paper) displays like these use the ambient light that falls on the display surface and reflects back to the eye of the observer, resulting in excellent readability under all conditions. Since reflective displays do not emit light but reflect it, they create almost zero light pollution and are not intrusive.
Electro wetting makes use of the surface tension of the liquids. A display consists of many tiny cells and each cell contains a transparent polar liquid and a colored oil that covers a hydrophobic surface. By applying a low voltage to the cells, the oil contracts into a small droplet. This creates an optical switch, which can be opened or closed. Since the displays are driven by voltage, without current flow, they are highly energy efficient. That makes the Electro Wetting Displays ultra low power.
In Etulipa’s EWD technology, the color displays are created by stacking three layers of cells above each other, with cyan, magenta and yellow respectively. Each layer has pixels that can be switched to an absorbing or a non-absorbing state. The whole surface area reflects the appropriate component of the light and this results in more saturated colors and better contrast than any other available color e-paper technologies.
Alternative e-paper technologies typically use an RGB approach. In the figure above, an example is shown in which red light is reflected from a simplified RGB-based display, and from a CMY stacked electro-wetting display. In the CMY approach the full area reflects incoming light, whereas in the RGB case only one third of the area reflects incoming light. The RGB approach will yield non-saturated colors.
Etulipa’s EWD technology has been specially developed for outdoor use. The displays can operate in all weather conditions, varying from extreme cold in the winter to very hot in the summer. Etulipa has tested Electro Wetting Display modules for their performace in outdoor applications according to the strict guidelines defined by Mil. Std. 810G*. Critical tests that are conducted involve performance and compliance at temperatures from -40 oC up to +70 oC to simulate conditions in everything from severe winter to hot summer weather, including induced heating from the sun.
* Mil. Std. 810G, Department of Defense Test Method Standard, Environmental Engineering Considerations and Laboratory Tests, 31 Oct 2008.
To enable high quality video displays, a high frame rate is required. EWD technology has the intrinsic capability to switch the droplets at high speed, which enables video displays to be produced.
There has been a long quest for digital outdoor displays that can be as abundant as paper-based ones. Up to now, light pollution and energy consumption meant that such displays were prohibited from fulfilling that role. This whitepaper explains why Etulipa’s Electro Wetting Display technology is at the forefront of this change. It gives a short overview of the basics of Electro Wetting Display technology, and goes on to explain why EWD technology will be successful where other technologies have failed so far.