The research into camouflage has been performed at Northeastern University, where researcher Professor Leila Deravi has been looking at the natural mechanisms of octopuses, squid, and cuttlefish.
The research team has been looking carefully at chromatophore organs. These resemble multi-colored freckles as found on the surface of a cephalopod’s body, in their hundreds. Chromatophores are pigment-containing and light-reflecting cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods, and they are found varying in shades of red, yellow, brown, and orange.
These organs lead to a rapid change in skin color, by opening and closing, which helps to resemble the sea creature near invisible. Underneath the chromatophores are layer of iridophores, which act as a type of mirror. The combination of chromatophores and iridophores lead to an ability of the creature to reflect all colors of visible light.
The key to the color change is pigment granules contained within the organs. The granules have special optical qualities. The researchers began their study by removing individual pigment particles from a squid, and subjecting these to analysis. The particles are very tiny, some 150 times smaller than the diameter of a human hair (500 nanometers).
According to Professor Deravi, who was speaking with Controlled Environments: “We’re showing these pigments are a powerful tool that can produce ultra-thin films that are really rich in colors.”
Hence by replicating the granules the researchers have created a series of thin films and fibers. These materials can be potentially incorporated into textiles, flexible displays, plus future color-changing technological devices. This ability is of great interest to the U.S. Army, which has supported the study through the Natick Soldier Research, Development and Engineering Center. An aim is to enable the military to create new covert capabilities for soldiers, by making them harder to spot by the opposite side in a conflict.
In a related development the researchers found that the pigments are able to scatter both visible and infrared light. The effect of this is to enhance brightness and light absorption, which happens due to the scattering light through and off the granules. This phenomenon could be replicated on the materials used to create solar cells, with the effect of increasing the absorption of sunlight and thus energy capture and storage.
The research has been published in the journal Advanced Optical Materials. The research paper is titled “Natural Light-Scattering Nanoparticles Enable Visible through Short-Wave Infrared Color Modulation.”
