Inspired by the natural design of the Hercules beetle, researchers have created a film that changes colour according to the ambient humidity.
In muggy weather, microscopic pockets in the insect's shell trap water, transforming the beetle (Dynastes hercules; pictured) from khaki-green to black. Seung-Yop Lee and Jungyul Park of Sogang University in Seoul and their colleagues generated porous plastic films with a structure similar to that of the beetle's cuticle. At 25% humidity, the material appears blue-green, but at 98% it changes to red.
A sensor made from the material would not need electricity and could be used in small medical or agricultural devices.
AM. INST. PHYS.