A research team led by the University of California, Irvine has discovered the cellular structures that enable squids to change their appearance. By studying squid skin cells in three dimensions, they identified the role of iridophores or iridocytes in squid mantle tissues. These light-manipulating cells contain columns of platelets made from a protein called reflectin, which function as Bragg reflectors to selectively transmit and reflect light at specific wavelengths.
The findings were published in Science, where researchers detailed how these natural mechanisms inspired them to create a multispectral composite material with adjustable visible and infrared properties. Alon Gorodetsky, UC Irvine associate professor of chemical and biomolecular engineering, explained: “In nature, many animals use Bragg reflectors for structural coloration.” He noted the remarkable ability of squids to transition from transparent to colored states due to specialized subcellular structures.
Roger Hanlon from the Marine Biological Laboratory provided access to squids and assisted in understanding the anatomy of iridophore-containing tissues. “These are longfin inshore squids – Doryteuthis pealeii – that are native to the Atlantic Ocean,” said Gorodetsky.
The team employed holotomography, a microscopy technique combining low-intensity light with quantitative phase imaging, revealing structural features within squid iridophore cells. Georgii Bogdanov, a UC Irvine postdoctoral researcher, stated: “Holotomography used the high refractive index of reflectin proteins to reveal sinusoidal refractive index distributions.”
Inspired by these discoveries, Gorodetsky’s team developed flexible materials capable of changing appearance using nanocolumnar sinusoidal Bragg reflectors and augmented them with infrared capabilities through nanostructured metal films. Aleksandra Strzelecka highlighted that these bioinspired materials can dynamically adjust appearances in response to stimuli.
Gorodetsky emphasized that insights gained from this study could enhance various optical technologies such as lasers and sensors. “This study is an exciting demonstration of the power of coupling basic and applied research,” he remarked.
The research received funding from the Defense Advanced Research Projects Agency and the Air Force Office of Scientific Research.
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