The colors on the liquid crystal display (LCD) can be controlled electrically, without the use of complex color filters, argue the chemists and physicists of the Military University of Technology. It is the only center in Poland where a specific electro-optical effect is investigated. In the future, it may be used in energy-saving TVs or smart windows.
On the glass of the smart window, you can display the lagoon or change its color to save energy. Such windows, as well as LCD with even better colors, obtained in a technologically simpler way — these are distant, but possible applications of the so-called cholesterics with an oblique helix.
“The effect of controlling an oblique helicoidal structure using an electric field” is investigated by Dr. Eng. Mateusz Mrukiewicz. The scientist brought this knowledge from Kent State University in Ohio and — as the only specialist in this field of research in Poland — he develops it at the Faculty of New Technologies and Chemistry of the Military University of Technology.
“Until ten years ago, material reflected only light of a given wavelength — that is, only green light, for example. And if we wanted red light, we had to heat the material or chemically modify it. We couldn’t do it immediately. There were simply no materials that would allow to obtain colors from ultraviolet to infrared in a very simple way”- explains Dr. Mateusz Mrukiewicz. Around 2010, a new class of liquid crystal materials with a bend shape — resembling bananas — was created. The mixtures of these molecules resulted in a spring structure, professionally known as an oblique helix. Previously, this spring could not be controlled. Today scientists are able to push and stretch it. By changing the electric field applied to such a material, it is possible to control the color of the reflected light In the materials produced at the Military University of Technology, researchers control the reflection of light using an electric field. In this way, they obtain a very wide range — from UV radiation to infrared. New materials must switch to different colors as quickly as possible. For now, this time is too long and strongly depends on the temperature. Dr. Mrukiewicz decreased the phase transition temperature in the liquid crystal and selected the composition of the mixture so that this effect could be obtained at room temperature. Scientists are on track to overcome this barrier and significantly reduce the response time of such a medium.
fot. Mateusz Mrukiewicz