Researchers have found a strange state of matter called "disordered hyperuniformity," in chicken eyes. This is the first time that this type of matter has been discovered in a biological system. The research could help advance optic circuits and create self-arranging materials.
Disordered hyperuniformity is when a matter behaves both like a crystal and a liquid. It is a crystal in a sense that the density of particles within the matter is same over large distances. However, at smaller distances, the particles behave like liquids by displaying same physical properties in all directions.
The presence of matter with disordered hyperuniformity in chicken eyes is nature's way of cramming several light-sensing cells or cones in a tiny space, researchers say. The arrangement has helped chickens develop "impeccable" vision.
The study was conducted by researchers at Princeton University and Washington University in St. Louis.
"Disordered hyperuniform materials possess a hidden order," explained co-corresponding author Salvatore Torquato, a Princeton professor of chemistry.
The state of disordered hyperuniformity was first described by Torquato and Frank Stillinger in 2003. Since then, the unique state of matter has been discovered in liquid helium and simple plasmas.
Now, Torquato and team have found disordered hyperuniformity in the eyes of chicken. Researchers studied cones or light-sensitive cells in the eyes of chickens.
Chickens have four types of cones for color- red, blue, green and violet- along with a fifth type that detects light levels. Each cone is different in size. The cones are packed into a layer of the eye called retina.
In other creatures, the packing is quite even with cones being arranged in a specific shape. However, in chicken eyes these cones seem to be scattered. The unusual arrangement was first spotted by Joseph Corbo, an associate professor of pathology, immunology, and genetics at Washington University in St. Louis, and colleagues.
Torquato and colleagues then developed a computer model to mimic the arrangement of cones in chicken eyes, Livescience reported.
Researchers found that each type of cone has an exclusion area around it that prevents similar cones from getting too close to each other. This selective separation leads to a pattern that might look scattered, but is in fact highly ordered.
"Because the cones are of different sizes it's not easy for the system to go into a crystal or ordered state," Torquato said in a news release. "The system is frustrated from finding what might be the optimal solution, which would be the typical ordered arrangement. While the pattern must be disordered, it must also be as uniform as possible. Thus, disordered hyperuniformity is an excellent solution."
The chicken study not only shows the presence of disordered hyperuniformity in biological systems, but also shows that birds have more advanced multi-hyperuniform structures in their eyes.
"You also can think of each one of these five different visual cones as hyperuniform," Torquato said. "If I gave you the avian system with these cones and removed the red, it's still hyperuniform. Now, let's remove the blue - what remains is still hyperuniform. That's never been seen in any system, physical or biological. If you had asked me to recreate this arrangement before I saw this data I might have initially said that it would be very difficult to do."
The study can help researchers create self-arranging materials that form hyperuniform states. Scientists could also take inspiration from chicken-eyes to create light detectors sensitive to only certain wavelengths, Livescience reported.
The study was funded by National Science Foundation, National Cancer Institute, the National Institutes of Health and the Simons Foundation.
The study was published in the journal Physical Review E.