Windows and mirrors embedded with liquid crystals can hide images that appear only when the right kind of light is shined on them. The technique, inspired by a 4000-year-old trick for building “magic mirrors”, may be a step towards developing better displays for 3D images.
A magic mirror or window looks transparent until a light is shined onto it to reveal a secret image. Craftspeople in ancient China and Japan made magic mirrors out of bronze that similarly hid images, but physicists only began to understand how they work around 15 years ago.
Felix Hufnagel at the University of Ottawa in Canada and his colleagues used those insights to build a new type of magic mirror and window. Their versions contain a state of matter known as a liquid crystal. While liquids flow freely and crystal atoms are organised in stiff grids, liquid crystals split the difference: their molecules are both fluid and arranged in patterns. READ MORE...
