Colloidal photonic crystals for displays?
The NewScientist is reporting on colloidal photonic crystals consisting of dispersions of magnetic iron oxide particles with a charged surface coating, developed by Yadong Yin and colleagues at the Department of Chemistry at University of California, Riverside.
The charged particles repel each other but their packing can be influenced by applying a magnetic field. Tuning the spacing of the particles in the colloidal crystal, by varying the magnetic field strength, changes the wavelength of the reflected light.
The crystal reflects brilliant colours from red to violet as the magnetic field strength increases (see image, right). But, when the field is switched off, the crystal reverts back to its original brownish colour.
“This is the first report of a photonic crystal that is fully tuneable in the visible range of the electromagnetic spectrum,” says Yin.
“We see applications in various areas, including sensors, optical switches and flexible colour displays,” he told New Scientist. “For example, the system can be used to make extra-large displays or posters to replace expensive LCD monitors. And, because the colour is based on reflection, it is better for outdoor applications than current LCD displays that perform poorly in direct sunlight.”
The work was reported in Angewandte Chemie International Edition.