Camouflage sheeting changes colour on demand
Designers in America have built flexible material
Using the camouflage abilities of octopuses as a starting point, engineers have built a flexible material that changes colour to match its surroundings.
The new design developed in the USA features a grid of 1mm cells, containing a temperature-driven dye that switches colour on demand.
So far it only responds in black-and-white, but the team hopes that the principles of their design will have commercial applications.
Senior author Prof John Rogers, from the University of Illinois, said the new sheet was the fruit of a collaboration between experts in biology, materials, computing and electrical engineering.
"Animals in the natural world - particularly cephalopods: octopus, squid and cuttlefish - have really spectacular colour-changing capabilities," he said..
Rogers' team set out to see what could be learned from such natural examples, and build a new material based on those insights.
In particular, they copied the three-layer design seen in the skin of these animals: the top layer contains the colours, the middle layer drives the colour changes, and the lower layer senses the background patterns to be copied.
Each component in the new sheets, however, does its job quite differently from the three layers that do the same job in an octopus's skin.
The bottom layer in the engineered system contains a grid of photosensors, which detect changes in light and transmit that pattern to "actuators" in the layer above.
These actuators take the place of muscles within octopus skin, which control colour-changing organs in the surface layer.
The uppermost layer in the artificial version uses a temperature-sensitive pigment, which goes from black to transparent at precisely 47C. That temperature change has to be produced by a current from the actuators underneath.