A group of South Korean scientists has developed a robot capable of changing color, an ability similar to that of the chameleon and other animals in nature. The research, published in the scientific journal Nature Communications on Tuesday (10), could revolutionize the camouflage industry, especially in its military use.
The development of artificial technologies to make objects “invisible” in the environment is not exactly new. Since 1800, studies have sought to develop a camouflage for military purposes, with the aim of increasing the survival capacity of soldiers and identifying objects from a specific army.
More recent studies, however, have a broader application. The team of researcher Seung Hwan Ko, from the Department of Medical Engineering at Seoul National University, created a new strategy with nanotechnology that can be applied to clothing, artificial skin, panels and other materials, with possibilities for use in medicine and even in fashion .
Some animals, such as the chameleon, have a natural ability to mimic the colors of their surroundings. (Source: Pixabay/Anrita1705/Reproduction)Source: Pixabay/Anrita1705/Reproduction
The first to understand the color change mechanism of chameleons and other lizards was scientist Earl Perkins, in 1930. In nature, these animals have a cell in their skin called a chromatophore, which can be expanded from an invisible point to a disk colored, giving color to a corresponding portion of the skin.
Each dermal layer contains chromatophores of different colors. Brown cells are closest to the surface, red and yellow cells are below brown, and blue and green cells are in the innermost layer. To appear green, the chameleon contracts the upper layers, allowing the green chromatophores, which have been expanded, to appear on the surface.
However, animals don’t change color just to become invisible. A series of simple experiments performed by Raymond Ditmars showed that chameleons changed their color in response to temperature, ambient light levels and according to the presence of other animals.
Like the chameleon in nature, the robot uses several layers of skin to display different colors. (Source: Nature Communications/Reproduction)Source: Nature Communications/Reproduction
While the camouflage found in nature depends primarily on the mechanical action of muscle cells, artificial technology does not necessarily need to match the actual colors of the environment. Therefore, it can also incorporate different strategies.
The newly developed artificial technology, instead of bands of colored skin cells, uses layers of liquid crystal that change their color according to temperature. However, the device alone cannot achieve a high resolution setting, and color patterns can appear pixelated, detrimental to camouflage.
To overcome this difficulty, the scientists used as a strategy the integration of the “thermochromic liquid crystal layer with standardized silver nanowire heaters stacked vertically in a multilayer structure.” With this, they were able to develop a more complete device to be applied in camouflage wearable on a robot.
In the article, the researchers point out that the technology developed is more practical than previous advances in artificial camouflage. According to the scientists, the experiment can be scalable, high-performance and used in complete devices, in addition to being compatible with the environmental conditions and movements of the object.
In other works, the same team of scientists made progress with the development of a flexible and lightweight material, such as a polymer, which simulates the movement and color changes of living bodies, composed of low density polyethylene (LDPE), chloride polyvinyl (PVC) and silver nanowires.
With the feature, materials change their appearance by bending in a certain direction when heated and return to their original shape when cooled. In this way, there is a twisting or bending depending on the temperature.
Unlike conventional robots, heavy and rigid, the new technology is lighter and more flexible, as it uses different types of macromolecular blades whose coefficient of thermal expansion varies according to their physical direction, allowing free movement.
Although animals’ ability to camouflage is more efficient and complex, this is a remarkable advance with multiple applications in science and everyday life.
ARTICLE Nature Communications: doi.org/10.1038/s41467-021-24916-w