UC Irvine Researchers Discover Squid's Color-Changing Abilities

By examining squid skin cells three-dimensionally, a University of California, Irvine-led team has unveiled the structures responsible for the creatures' ability to dynamically change their appearance from transparent to arbitrarily colored states.

The group of scientists found that in vibrantly colored squid mantle tissues, light-manipulating cells called iridophores or iridocytes contain stacked and winding columns of platelets from a protein called reflectin, with the columns functioning as Bragg reflectors that selectively transmit and reflect light at specific wavelengths.

In a paper published today in Science, the researchers discussed how they took inspiration from the cells and their internal columnar structures to develop a multispectral composite material with adjustable visible and infrared properties.

Co-author Alon Gorodetsky, UC Irvine associate professor of chemical and biomolecular engineering, said, \"A squid's ability to rapidly and reversibly transition from transparent to colored is remarkable, and we found that cells containing specialized subcellular columnar structures with sinusoidal refractive index distributions enable the squid to achieve such feats.\"

Co-author Roger Hanlon, a senior scientist with the Marine Biological Laboratory, provided Gorodetsky's UC Irvine team with access to squids, and his laboratory helped unravel the coloration and anatomy of the iridophore-containing tissues.

The team used holotomography, a microscopy technique that combines low-intensity light with quantitative phase imaging to create 3D images of clustered and individual cells.

Co-lead author Georgii Bogdanov, a UC Irvine postdoctoral researcher in chemical and biomolecular engineering, said, \"Holotomography used the high refractive index of reflectin proteins to reveal the presence of sinusoidal refractive index distributions within squid iridophore cells.\"

Co-lead author Aleksandra Strzelecka, Ph.D. candidate in chemical and biomolecular engineering, mentioned, \"These bioinspired materials go beyond simple static color control, as they can dynamically adjust both their appearances in the visible and infrared wavelengths in response to environmental or mechanical stimuli.\"

Gorodetsky highlighted that the insights gained from studying squid skin can be leveraged for improving optical technologies such as lasers, fiber optics, photovoltaics, and sensors.

The research was funded by the Defense Advanced Research Projects Agency and the Air Force Office of Scientific Research.

About the University of California, Irvine: Founded in 1965, UC Irvine is a member of the prestigious Association of American Universities and is ranked among the nation's top 10 public universities by U.S. News & World Report.

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