A remotely controlled material created by MIT researchers can change its colour, texture and fluorescence on demand, providing perfect camouflage.
Inspired by the ability of octopuses, squid and cuttlefish to change the colour and texture of their skin within seconds to blend perfectly into the environment and escape the attention of predators, the material could serve in military applications but could also be used to produce large flexible display screens.
The pioneering study, led by Massachusetts Institute of Technology (MIT) assistant professor of Mechanical Engineering Xuanhe Zhao and Duke University professor of chemistry Stephen Craig, was published in the latest issue of the journal Nature Communications.
Zhao said the material is based on readily available components and consists essentially of a layer of electro-active elastomer, a flexible, stretchable polymer that could be quite easily adapted to standard manufacturing processes.
“It changes its fluorescence and texture together, in response to a change in voltage applied to it – essentially, changing at the flip of a switch,” said MIT postdoc Qiming Wang.
The team has first discovered the ability of elastomers to change surface texture and colour in reaction to applying voltage in 2011.
“The texturing and deformation of the elastomer further activates special mechanically responsive molecules embedded in the elastomer, which causes it to fluoresce or change colour in response to voltage changes,” explained Prof Craig. “Once you release the voltage, both the elastomer and the molecules return to their relaxed state – like the cephalopod skin with muscles relaxed.”
The team believes the availability of the material makes it a more economic contender for a future military camouflage material than other technologies that are assembled from individually manufactured electronic modules.
In its initial proof-of-concept demonstrations, the material can be configured to respond with changes in both texture and fluorescence, or texture and colour. In addition, while the present version can produce a limited range of colours, there is no reason that the range of the palette cannot be increased, said Prof Craig.
Cephalopods achieve their remarkable colour changes using muscles that can alter the shapes of tiny pigment sacs within the skin – for example contracting to change a barely visible round blob of colour into a wide, flattened shape that is clearly seen.
“In a relaxed state it is very small,” Zhao said, but when the muscles contract, “they stretch that ball into a pancake, and use that to change colour. The muscle contraction also varies skin textures, for example, from smooth to bumpy.”
While troops and vehicles often move from one environment to another, they are presently limited to fixed camouflage patterns that might be effective in one environment but not in another. Using a system like this new elastomer, Zhao suggests, either on uniforms or on vehicles, could allow the camouflage patterns to actively respond to the surroundings.
“The US military spends millions developing different kinds of camouflage patterns, but they are all static,” Zhao said. “Modern warfare requires troops to deploy in many different environments during single missions. This system could potentially allow dynamic camouflage in different environments.”
The material could also serve as anti-fouling coating on the hulls of ships, which are vulnerable to accumulating microbes and barnacles. Earlier experiments have shown that even a brief change in the surface texture, from the smooth surface needed for fast movement to a rough, bumpy texture, can quickly remove more than 90 per cent of the biological material.
The project was supported by the US Office of Naval Research, the US Army Research Laboratory and Army Research Office, and the National Science Foundation.