Inspired by the small but extremely deadly blue-ringed octopus, researchers have created a new technology that can rapidly change color and appearance in various lights for camouflage and signaling. This technology is expected to be used in fields such as military, medicine and robotics.
The great blue-ringed octopus (Hapalochlaenalunulata) uses split-second muscle contractions to change the size and color of its colorful skin patterns to camouflage itself, hide from potential predators, and send warning signals to other animals. This contraction stretches or compresses the chromaffin cells, the small balloon-like pigment sacs in the skin.
Inspired by cephalopods' ability to deceive and signal, researchers at the University of California, Irvine (UCI) have created a technology platform that mimics it.
Alon Gorodetsky, corresponding author of the study, said: "We are fascinated by the mechanism by which the blue-ringed octopus rapidly switches skin markings between hidden and exposed states. In this project, we strived to mimic the octopus's natural abilities with a device made from a unique material that we synthesized in the laboratory. The result is an octopus-inspired deception and signaling system that can be directly fabricated, function for long periods of time under continuous operation, and even self-repair when damaged."
The technology is structurally very similar to the rings of a blue-ringed octopus: a transparent proton-conducting polymer electrode on top, a nonene-based active layer (in which a wrinkled blue ring surrounds a flatter brown circle), an underlying acrylic membrane, and a transparent proton-conducting polymer electrode on the bottom. Nonene-based designer molecules help give the platform some functionality.
"In this device, we conceived and designed a non-olefinic molecule with a unique structure," said Preeta Pratakshya, first author of the study. "Ene is an organic hydrocarbon molecule with a range of advantageous properties, including ease of synthesis, tunable electronic properties, and controllable optical properties. Our non-olefin molecules are the best among the olefins because they can be stored in air for years and survive continuous exposure to strong light in air for more than a day. No other expanded olefin displays such comprehensive long-term stability under such harsh conditions."
In addition to being highly tolerant, these molecules endow the technology with other important blue-ring-inspired properties, including tunable spectral properties, direct fabrication on the desktop using minimal equipment, and ambient-atmospheric stability under light.
The system continues to reliably change its visible light appearance approximately 500 times, with minimal to no functional degradation under environmental conditions. It demonstrates its capabilities in the ultraviolet-visible-near-infrared (UV-Vis-NIR) region of the electromagnetic spectrum, including the ability to modulate visible color brightness, change near-infrared contrast, and adjust multispectral fluorescence intensity. The researchers say this capability would allow the technology to camouflage other objects without being detected, or covertly signal to observers. Unexpectedly, the researchers found that the technology can also repair itself autonomously without user intervention.
"The photophysical robustness and general processability of our nonene-like molecule - and presumably its variants - opens up opportunities for future studies of these compounds in conventional optoelectronic systems such as light-emitting diodes and solar cells," Gorodetzky said.
The researchers say their easy-to-make technology could have applications in military, medicine, robotics and sustainable energy fields. Its scalability means it can be used to cover large areas such as vehicles, billboards and even buildings.
The study was published in the journal Nature Communications, and the video below, produced by Gorodeski's team, compares the color-changing abilities of the blue-ringed octopus with bio-inspired technology.