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Could tomorrow’s buildings change colour like squid do?

Words:
Stephen Cousins

An ‘artificial muscle’ that changes colour in the way cephalopods do when contracting in response to light could be used as a material for screens and even wall claddings

Juvenile squid photographed at night in waters of Raja Ampat, Indonesia.
Juvenile squid photographed at night in waters of Raja Ampat, Indonesia. Credit: iStock

The chameleon-like ability of octopuses, squids and cuttlefish to camouflage themselves by changing colour and shape has been harnessed by scientists in the US to create a synthetic material that could be used in flexible screen displays or even undulating wall surface coatings or cladding.

Researchers at Rutgers University in New Jersey created an ‘artificial muscle’ in the form of 3D-printed smart gel that changes shape when exposed to light when combined with a 3D-printed stretchy material it reveals colours when light changes. The findings were reported in a study in the journal ACS Applied Materials & Interfaces

The team claims the findings support a new engineering approach whereby camouflage is added to soft materials to create flexible, colourful displays, unlike current displays that must use rigid materials, limiting how they can interface with 3D surfaces.

The process could also support the development of new types of military camouflage, or soft robotics. Applications in architectural engineering have not yet been explored, but the technology could underpin innovations here too.

It would be interesting if one could build a building with changing surface colour, perhaps depending on varying light conditions throughout a day or a year

Professor Howon Lee, senior author of the report and assistant professor in the Department of Mechanical and Aerospace Engineering, told RIBAJ: ‘It would be interesting if one could build a building with changing surface colour, perhaps depending on varying light conditions throughout a day or a year.’

Cephalopods, like squids and cuttlefish, use chromatophores distributed on their soft skin to create extremely complex skin colour patterns used for camouflage and communication.

A central sack in each chromatophore contains pigment granules. Radial muscles surrounding the sack contract causing it to expand, making the colour of the pigment more visible.

Inspired by this mechanism, the engineers incorporated a light-sensing nanomaterial into hydrogel, turning it into an artificial muscle that contracts in response to changes in light. When combined with the 3D-printed stretchy material, the smart gel changes colour, resulting in a camouflage effect.

Next steps in the research include improving the technology’s sensitivity, response time, scalability, packaging and durability. Improvements to sensitivity could enable the gel to function in outdoor applications, such as on building surfaces, says Lee: ‘The material currently works under artificial light (intense light from a digital projector), but it could be possible to use a solar light if we improve the sensitivity.’

Something to ponder next time you’re tucking into some calamari.

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