Gradient refractive indices enable squid structural color and inspire multispectral materials.

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Title: Gradient refractive indices enable squid structural color and inspire multispectral materials.
Authors: Bogdanov, Georgii, Strzelecka, Aleksandra Anna, Kaimal, Nikhil, Senft, Stephen L., Lee, Sanghoon, Hanlon, Roger T., Gorodetsky, Alon A.
Source: Science. 6/26/2025, Vol. 388 Issue 6754, p1389-1395. 7p.
Subjects: Structural colors, Refractive index, Iridescence, Optical interference, Bragg gratings
Abstract: The manipulation of light by means of materials with varying refractive index distributions is widespread among natural systems and modern technologies. However, understanding how animals leverage refractive index differences for dynamic color changes and then translating such insight into tunable optical devices remains challenging. We experimentally and computationally demonstrated that iridescent cells (iridophores) containing Bragg reflectors with sinusoidal-wave (rugate) refractive index profiles enable squid dorsal mantle tissues to reversibly transition between nearly transparent and vibrantly colored states. We then drew inspiration from these findings for the design and development of iridophore-inspired multispectral composite materials with tunable visible and infrared functionalities. Our study provides insight into squid dynamic structural coloration mechanisms and furnishes a technology for camouflage, heat management, display, and sensing applications. Editor's summary: Squids and octopuses are known for their rapid adaptive coloration, an ability that enables them to effectively camouflage and that is also used for communication. Bogdanov et al. performed a detailed examination of the cells (iridophores) and cell clusters (splotches) that produce these colors (see the Perspective by Shawkey). There was a complex distribution of cells and other components that exhibit gradient refractive indices arising from their constituent winding platelet columns, resulting in structural color. Computational modeling of this system supported the design of artificially fabricated nanostructures that show tunable visible and infrared spectral responses. The authors implemented these structures in complex materials such as fabric and clothing. —Marc S. Lavine [ABSTRACT FROM AUTHOR]
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Database: Psychology and Behavioral Sciences Collection
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Abstract:The manipulation of light by means of materials with varying refractive index distributions is widespread among natural systems and modern technologies. However, understanding how animals leverage refractive index differences for dynamic color changes and then translating such insight into tunable optical devices remains challenging. We experimentally and computationally demonstrated that iridescent cells (iridophores) containing Bragg reflectors with sinusoidal-wave (rugate) refractive index profiles enable squid dorsal mantle tissues to reversibly transition between nearly transparent and vibrantly colored states. We then drew inspiration from these findings for the design and development of iridophore-inspired multispectral composite materials with tunable visible and infrared functionalities. Our study provides insight into squid dynamic structural coloration mechanisms and furnishes a technology for camouflage, heat management, display, and sensing applications. Editor's summary: Squids and octopuses are known for their rapid adaptive coloration, an ability that enables them to effectively camouflage and that is also used for communication. Bogdanov et al. performed a detailed examination of the cells (iridophores) and cell clusters (splotches) that produce these colors (see the Perspective by Shawkey). There was a complex distribution of cells and other components that exhibit gradient refractive indices arising from their constituent winding platelet columns, resulting in structural color. Computational modeling of this system supported the design of artificially fabricated nanostructures that show tunable visible and infrared spectral responses. The authors implemented these structures in complex materials such as fabric and clothing. —Marc S. Lavine [ABSTRACT FROM AUTHOR]
ISSN:00368075
DOI:10.1126/science.adn1570