Now you see them, now you don't

17 Jun 2002

Crystals that change shape and color could transform optical communications networks.

Scientists at Kyushu University in Fukuoka, Japan have discovered that shining light on single crystals of diarylethane produces two unusual reactions. Alternately shining ultraviolet light and then visible light on the crystals creates and then removes a series of tiny steps and valleys. The irradiation process also activates a reversible photochromic reaction in which the crystals' color changes from transparent to blue, and then back again.

The scientists believe that the way in which the molecules are packed within the crystal is sensitive to different wavelengths of light, and this induces the shape changes.

"The photochromic crystals are fatigue-resistant," Masashi Horichi and colleagues claimed in Science 291 176. "This means that the reversible morphological changes are potentially applicable to photodriven, nanometer-scale actuators."