Cephalopod skin is the inspiration of new generation camouflage clothing.
Octopuses are able to change color nearly instantly, in order to blend in with their surroundings. The animals do this both to hide from predators, as well as to sneak up on animals they are hunting.
A color-changing sheet has been developed by researchers, able to change colors in response to temperature. When cool, the material is black, turning clear when warmed above 116 degrees Fahrenheit.
Color-changing sheets were created by taking a layer of this material, and laying it on top of a silver sheet, in order to provide reflection of light. Thermal circuits, manufactured from silicon, are layered beneath these sheets, controlling heating. A layer of transparent silicone rubber underlies the whole structure, supplying support. The entire sheet measures just twice the thickness of an average human hair.
Photo receptors beneath this sandwiched device are able to read colors of light in the local environment, and direct color changes. Although the new device responds only in black and white, it is able to respond to changing conditions in less than two seconds. This is carried out autonomously, without the need for human input or direction.
Future development of the device could focus on designing new models that reflect different colors of light, or are triggered by electricity, rather than heat. The sheet consumes large amounts of energy, a cost which will have to be reduced if the invention is to become commonplace.
"This is by no means a deployable camouflage system but it's a pretty good starting point," John Rogers of the University of Illinois at Urbana-Champaign (UoI), co-leader of the study, said.
Military, consumer and industrial applications could benefit from development of camouflage derived from this new discovery. The flexible material could be used to hide equipment - or people - from observation in visible wavelengths of light.
Cephalopods carry out their color-changing behavior using a three-layer system. The bottom layer reflects white light, providing a backdrop for the biological system. The next layer reflects blue and green hues, common underwater, using cells called iridophores. Above these, controlling the entire system, is the top layer rich in chromatophores containing pigments controlled by muscles near the cephalopod skin. Also present in this upper layer are light receptors called opsins, similar to those found in human eyes. Although the purpose of these structures is not certain, most biologists believe they allow the skin of the animal to detect surrounding colors.
"Our device sees color and matches it. It reads the environment using thermochromatic material," Yonggang Huang of Northwestern University said.
Invention of the new color-changing sheet was detailed in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).
