Physics

Technology you can wear

Imagine a monitor, as thin and flexible as paper, that you could take everywhere you go and could use as your daily newspaper or your TV screen. William Skene, Associate Professor in Université de Montréal’s Department of Chemistry, heads a research group working to develop polymer structures, an essential ingredient of this new generation of screens known as Organic Light Emitting Diodes (OLED).

From computer and portable telephone screens to ad panels and revolutionary textiles, “the sky’s the limit when it comes to the applications of this new screen,” states the chemist, enthusiastically. The screen can take on a number of forms and is impervious to changes in temperature, thanks to its high resolution, ultra-thinness, low energy consumption as well as flexible and easy-to-transport format. The result: the screens can be applied to curved surfaces without losing the image when they bend. The technology opens the door to a whole new world of clothes, books and film.

“People won’t be walking around with TV screens on their shirts next week, but this technology is going to take off in the next 10 years,” states this materials specialist. OLED is composed of an emitting layer placed between two transparent electrodes; a current passes between the electrodes and the recombination of charges causes a colour emission, the result of an electrochemical reaction. In other words, the screen’s components generate the colour. Companies like Kodak, Phillips, Pioneer and Dupont are keeping a close eye on this technology and funding much of the research.

First-generation screens used cathode-ray tubes, a large, cumbersome and heavy technology that was employed in the very first TV sets and home computer screens. The current technology uses liquid crystals. Liquid crystal displays abound and can be found in flat screens and laptop computers, as well as calculator screens and electronic agendas, such as Palm Pilots. This technology, in which liquid crystals are applied to a hard surface and backlit, represented a major leap forward, but has two major drawbacks: its brittleness and unidirectional light emission. If the viewer is not directly in front of the screen, the image becomes fuzzy.

The development of a third generation of screens has created a lot of enthusiasm in the technological world. OLED works on the basis of organic materials such as carbon, hydrogen, oxygen and sulphur. Its revolutionary dimension, explains William Skene, comes from it being based on a chemical reaction, much like a battery. This reaction produces an energy emission in the form of light. “Based on the wavelength on the spectrum and the chemical composition, we can deduce the colour that will be emitted,” explains the researcher.

One of the hurdles that still needs to be overcome is the energy loss that occurs between the surface of the screen and the electrical layer. One way to improve its energy efficiency is to add a ‘hole injection layer’. This is where William Skene has now set his sights. His approach is to “take a series of little steps, instead of one big leap”. This additional layer is composed of the new polymers that act as conductors, something plastics have been unable to do. Unfortunately, we’re going to have to sit tight—this revolutionary breakthrough won’t be perfected for another decade.