Northeastern researcher Leila Deravi displays spools of thread that were created using squid pigment. Credit: Adam Glanzman/Northeastern University
The properties that enable squid and octopi to quickly change their appearance may inspire a new class of camouflage materials.
A team from Northeastern University has found that the chromatophore organs of cephalopods–which appear as hundreds of red, yellow, brown and orange freckles and contribute to fast changes in the animal’s skin color—have the optical qualities that could be used to make thin films and fibers. These could be incorporated into textiles, flexible displays and future color-changing devices.
“For more than a decade, scientists and engineers have been trying to replicate this process and build these devices that can color match, color change, and camouflage just like the cephalopods, but many of them come nowhere near the speed or dynamic range of color that the animals can display,” Deravi said. “Cephalopods have evolved to incorporate these specific pigment granules for a reason, and we’re starting to piece together what that reason is.”
The researchers isolated the pigment granules within the organs of cephalopods, which includes octopi, squid and cuttlefish, to get a better understanding of their role in color change. The cephalopods “freckles” open and close within a fraction of a second to give rise to a continuously reconfiguring skin color. Underneath the chromatophores is a layer of iridophores that act as a mirror. Together, the organs are able to reflect all colors of visible light.
By removing individual pigment particles—which are only 500 nanometers in size— from a squid, the researchers are able to explore the breadth of their capabilities as static materials by layering and reorganizing the particles. By doing this, the scientists found they could produce an expansive color pallet.
“We’re showing these pigments are a powerful tool that can produce ultra-thin films that are really rich in colors,” Leila Deravi, an assistant professor of chemistry and chemical biology at Northeastern, said in a statement.
The researchers also found that the pigments could scatter both visible and infrared light, enhancing brightness and light absorption and affecting how a final color is perceived. When they engineered a system that included a mirror to mimic the layout of organs that squids have naturally, the researchers were able to further enhance the perceived color through scattering light through and off the granules.
The process could possibly be replicated on functional materials like solar cells to increase the absorption of sunlight.
“From a scientific and technical engineering perspective, understanding how light scattering affects color is very important, and this is an exciting new development in the field of optics in biology,” Richard Osgood, a collaborator from the U.S. Army Natick Soldier Research, Development, and Engineering Center, said in a statement. “This is an unusual harnessing of optics and physics knowledge in scattering to understand biological systems.”
“For more than a decade, scientists and engineers have been trying to replicate this process and build these devices that can color match, color change, and camouflage just like the cephalopods, but many of them come nowhere near the speed or dynamic range of color that the animals can display,” Deravi said. “Cephalopods have evolved to incorporate these specific pigment granules for a reason, and we’re starting to piece together what that reason is.”
