The project "Electrophoretic Displays for Urban Traffic Information and Control" is concerned with the development of new display media exploiting the technologies of electrophoresis and dynamic retroreflectivity. The investigators seek to develop bi-stable display technology that uses electrophoresis (the movement of particles under influence of an electric field) that is suitable for large-scale outdoor applications, and that is switchably retroreflective. This will result in displays that act like static traffic signs when that is desirable, but which are seemingly invisible otherwise. The project requires the development of colored retroreflective particles that can be embedded in a transparent colloidal medium, and then made to react to the presence of an electric field with both translational and rotational movements. This will enable both color changes and the activiation/de-activation of retroreflectivity. The particles must be partially silvered, and then "blackened" via various deposition processes. The protective container must consist on one side of a transparent electrode, allowing for both the generation of an electric field but also the visibility of the particles. Some samples have been constructed with indium tin oxide, and more research along these lines will be conducted as part of the current project. The initial planned application is a set of pavement markers that alternate with the setting of the traffic signal controller, and which appear to be bright and reflective to that movement with the green light, but dark and nearly invisible to any other vehicles. This will greatly improve guidance while reducing visible clutter and confusion at complicated intersections, particularly at night.
The project "Electrophoretic Displays for Urban Traffic Information and Control" is a very nice blend of information technology and civil infrastructure development. By exploiting physical phenomena that allow tiny particles to move and rotate under the influence of electric fields, signs and other forms of displays can be constructed that are dynamic, use very little power, require no form of direct illumination, and can be used in harsh environments such as embedded in pavement, yet they are visible at night and look much more "natural" than traditional garish highway signs. They do not require external illumination because they use a technology called switchable retroreflectivity to reflect light from vehicle headlamps back to drivers when it is desired to do so. As a result, they do not add to visual clutter, confusion, and the poor aesthetics typical of most highway-related nighttime illuminated signs. The basic electrophoretic technology is derived from methods used currently to produce small-scale electronic displays, wrist watches, and various forms of "electronic paper." Initially, investigators are focusing on highway-related applications such as dynamic pavement markers at complicated intersections, variable message signs, and variable pavement markings. In the future, other applications such as airfield and taxiway signage, curb paint that can change color, and messages on tunnel walls can be considered.
