Living Photonic Crystals: These scanning electron microscope images of tiny diatoms have been digitally colored. But in real life, their glass-like skeletons have a special property of interfering with light waves, reflecting light in different colors depending on the viewer’s angle, much like an oil slick on water. This is because the array of tiny holes studding the diatom surface match the wavelength of visible light and behave as photonic crystals.
• Photonic crystals are optical nanostructures which affect the path of photons just as semiconductors affect electrons. They have periodic (repeating) changes in dielectric constant. Photons pass through this structure – or not – depending on their wavelength. The repeating pattern of solid and water filled holes on diatoms make them natural photonic crystals.
• Diatoms could be used to make iridescent cosmetics, paints and fabrics and even credit card holograms. They are cost-effective and biodegradable. Up to 1 tonne of diatoms can be made per day, starting with only a few cells. Diatoms are microscopic, photosynthesizing single celled microorganisms. Did you know that they produce a quarter of the oxygen that we breathe?
Images: Diatoms looking like various artifacts, from a pill box to a peanut were selected from http://www.flickr.com/photos/galfaye/