Chameleons are known for concealing themselves, interact, and control their temperature through changing their colors. Two different researchers took influence from the chameleon project and created devices that can modify the material's color.
Chinese scientists made a versatile anti-counterfeiting film that varies based on stretch, pressure, or humidity. Researchers from the University of Cambridge produced large-scale interactive displays through artificial 'chameleon skin in a separate report.
Anti-counterfeiting film
Scientists presented a flexible film that changes depending on stretch, strain, or humidity. They presented their report to ACS Advanced Materials & Interfaces.
Chameleons may alter the way light absorbs from guanine crystals under the surface by tightening or relaxing their skin, creating what is known as structural coloration.
These structural colors are distinct from the pigments that lend their hues to many other species.
In different color-changing materials, scientists have imitated the crystalline nanostructures of chameleon skin, but they are usually hard to make or dependent on non-renewable petroleum supplies.
On the other hand, cellulose nanocrystals are a sustainable substance that can self-assemble with iridescent structural colors into a film.
The films, though, are usually delicate and can't be extended without cracking, unlike chameleon skin.
Fei Song, Yu-Zhong Wang, and colleagues wanted to create a highly flexible film made of nanocrystals of cellulose, which changes color when stretched.
The researchers applied a polymer named PEGDA to improve the durability of cellulose nanocrystals.
They used UV light to crosslink it to the rod-shaped nanocrystals, creating films of vivid iridescent colors varying from blue to red, depending on the volume of PEGDA.
The films were both reliable and resilient, extending until splitting up to 39 percent of their initial runtime.
One film's color steadily shifted from red to green while stretching, and then shifted again when relaxed.
According to researchers, this is the first time cellulose nanocrystal products can move and change dazzling color noticeable to the naked eye.
The film often changed color with pressure and humidity, enabling the team to reveal or cover writing created from an inkless pen.
Researchers added the latest bio-based smart skin might find applications in strain sensing, cryptography, and anti-counterfeiting controls.
Interactive displays
Researchers from the University of Cambridge produced large-scale interactive displays through artificial 'chameleon skin.'
The researchers created the substance from tiny gold particles wrapped in a polymer shell and then squeezed it into oil-based water microdroplets.
The particles bind together when subjected to heat or light, altering the appearance of the substance. In the journal Advanced Optical Materials, the findings are published.
As the substance is heated past 32C, the nanoparticles accumulate significant quantities of elastic energy in a fraction of a second when the polymer coatings remove all the water and collapse.
This has the effect of pulling the nanoparticles into small clusters to link together. The polymers take on water and grow as the substance is cooled, and the gold nanoparticles, like a spring, are firmly and rapidly forced apart.
When they bind into groups, the nanoparticles' geometry dictates what color they look as they are red when the nanoparticles are spaced apart and dark blue when they cluster together.
Though, the droplets of water often compact the clusters of particles, allowing them to shade each other and rendering the clustered state almost invisible.
Study co-author Sean Cormier said the study is a significant development in the usage of nanoscale biomimicry technologies. "We're now working to replicate this on roll-to-roll films so that we can make meters of color-changing sheets," he added.
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