Robots Now Have Chameleon Skin?
Although this may not be the first colour-changing material that responds to movement, such as bending and twisting, it is the first that can be printed and programmed to display different patterns. The film would be coated onto the machines which would allow the robots to communicate with humans quickly, simply by altering its shade. The team achieved this film by significantly reducing the size of the gold nanoparticles.
In our case, we reduced gold to nano-sized rods. We knew that if we could make the rods point in a particular direction, we could control their colour. Facing one way, they might appear red. Move them 45 degrees, and they change to green.
An example would be a camouflaged robot entering underwater crevices. If the robot changes colour due to the pressure of the water, biologists could learn how animals are able to live in these environments.
However, a problem that the research team were tasked with was the goal of taking millions of gold nanorods floating in a liquid solution and guiding them to the same direction to display a uniform colour.
The solution to this issue was the fusion of smaller magnetic nanorods onto the larger gold ones and compress them both in a polymer shield. This would allow the orientation of both rods to be controlled by the magnets.
Just like if you hold a magnet over a pile of needles, they all point in the same direction. That’s how we control the colour.
Once dried into a thin film, the orientation is fixed in place and no longer responds to the magnets.
Other materials such as butterfly wings can also change colour when observed at different angles. However, those materials rely on precisely ordered microstructures which is difficult and expensive to make for larger areas. This novel film is both inexpensive and convenient to make; it can be engineered to coat the surface of any sized objects just as easily as applying spray paint.
New material with programmable colorimetric responses can behave more like animal skins. Image Credit: Phsy.Org
This film can be used in many different ways. UC Riverside chemist, Zhiwei Li, the first author on this paper, explained that the film can be integrated into cash as an authentication feature. Under standard lighting, the film is grey, but when you see it through a polarised lens, complex and elaborate patterns can be identified. In addition, the colour contrast of the film may change drastically if the film is twisted.
Artists could use this technology to create fascinating paintings that are wildly different depending on the angle from which they are viewed. It would be wonderful to see how the science in our work could be combined with the beauty of art.
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