The intersection of nature and technology has inspired many advanced 3D printing projects, from Lilian van Daal’s 3D printed Biomimicry chair to these 3D printed water-cleaning robots inspired by real bugs. Taking biomimicry and bio-inspired science to the next level, students from Wuhan University in China and Georgia Institute of Technology have created a mechnical chameleon robot, encased in a 3D printed shell, that can actually change its color to blend into its surroundings. Future applications include allowing military vehicles or even body armor to seamlessly camouflage with their backgrounds, just as they would with a real-life invisibility cloak.
The chameleon robot consists of a 3D printed ABS shell, created with a Da Vinci 1.0 desktop 3D printer, covered in plasmonic displays. In physics, plasmons play a large role in the optical properties of metals and semiconductors, and plasmonic metamaterials, produced from the interaction of light with metal-dialectric materials, can achieve optical properties not usually seen in nature.
“Optical invisibility represents one of the greatest challenges in military and biomimetic research,” said the researchers. “We report a method based on the combination of bimetallic nanodot arrays and electrochemical bias, to allow for plasmonic modulation. Importantly, our approach permits real-time like manipulation readily matchable to the color setting in a given environment. We utilize this capability to fabricate a biomimetic mechanical chameleon and an active matrix display with dynamic color rendering covering almost the entire visible region.”
Essentially, tthe researchers created plasmonic nanostructures based on highly ordered gold (Au) and silver (Ag) nanodomes, which exploit the interactions between nanoscale structures and electric fields.
Let’s start with the nanoscale structures. To create these, the researchers took a glass sheet and covered with a grid of miniscule holes, each of which was filled with gold nanoparticles. Thus, each hole contained its own gold 'nanodome'. The glass sheet was then placed inside a casing filled with an electrolyte gel containing silver ions. Light hitting the gold nanodomes produces the plasmons, which determine the glass sheet’s reflective and absorbing properties.
Next, by applying an electric field to the plasmonic display, (which can later be reversed), silver ions are deposited onto the gold nanodomes, modifying their properties and producing different colors. Several sensors are embedded onto the body of the robot chameleon, which can detect the color of the surroundings and translate that information to the microcontrol system, which applies the correct voltage to the corresponding plasmonic field and effectively changes its color to match the background.
It is, undoubtedly, a very complex technical phenomenon, however the video below speaks for itself: the robot moves from a red background to a green one, adapting the color of its surface in real-time from front to back, with no color switching until the sensors fully moves into the next color background. The same process is repeated as it moves from a green background to a blue one. “Evidently, the mechanical chameleon possesses every fundamental feature that is needed for realistic active camouflage,” said the researchers.
Though the current sensors can only recognize three primary colors (red, green and blue), the researchers have said that their technology can interface with a complex environment and provide a new approach for artificial active camouflage, and that more technically advanced autonomous systems could capture and simulate the entire color patterns of a given environment, “fully merging the mechanical chameleon with the surroundings.”
This method of combining 3D printing, bimetallic plasmonic displays and electrochemical bias could eventually be used in military applications, and to help further biomimetic research. The full details of the research were published in a paper titled “Mechanical Chameleon through Dynamic Real-Time Plasmonic Tuning,” in the ASC journal Nano. The authors are Xuechen Chen and Sheng Chu of Sun Yat-Sen Univeristy in Guangzhou; Guoping Wang and Sheng Liu of Wuhan University, and Chingping Wong of the Georgia Institute of Technology.
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