Squid skin: Infrared biomimetic nanoparticles

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  • Published: Mar 1, 2018
  • Author: David Bradley
  • Channels: Infrared Spectroscopy
thumbnail image: Squid skin: Infrared biomimetic nanoparticles

Pigment pallet

Researchers made spools of fibers from the squids’ pigment particles and are now exploring uses for the material. The fibers are so visually interesting that it’s not difficult to imagine weaving them into fabric for clothing or other art forms. But perhaps the most exciting possible application is wearable, flexible screens and textiles that are capable of adaptive coloration. Photo by Adam Glanzman/Northeastern University

Nanoparticles that mimic the properties of squid skin can modulate electromagnetic radiation in the visible to short-wave infrared region, according to British scientists. Leila Deravi of Northeastern University and her colleagues recognized that cephalopods, such as cuttlefish, octopuses, and squid can be very efficient at camouflaging themselves from both prey and predator. Colour changing their skin allows them to match their surroundings very rapidly but science is yet to reproduce this evolutionary trick. Deravi and her team have swum a little closer to being able to do so.

The multicoloured spots, the chromatophores, in the surface of a cephalopod's skin underpin the animals' ability to change skin colour quickly. Writing in the journal Advanced Optical Materials, the team group explains how they have isolated the pigment granules within the skin colour organs. The idea being to better understand their role in colour change.

The chromatophores come in different hues: red, yellow, brown, and orange. These spots can open and close within a fraction of a second to give rise to a continuously shifting pattern of skin colour. Beneath the chromatophore layer is a later of iridophores which act as a mirror. Together, these organs reflect all colours of visible light. By removing individual pigment particles from the squid, Deravi was able to explore the breadth of their capabilities as static materials. One particle is only 500 nanometres across. The researchers layered and reorganized the particles and found they could produce an expansive colour pallet.

Granular scattering

The team found that the granules have some additional intriguing optical qualities and they have now used them to fabricate thin films and fibres. Such materials or derivatives thereof might one day be incorporated into wearable technology, flexible displays, and future colour-changing devices. "We're showing these pigments are a powerful tool that can produce ultra-thin films that are really rich in colours," Deravi explains.

Moreover, the team has demonstrated that these pigments can scatter both visible and infrared light. This enhances brightness and light absorption and affects how the final colour is perceived in the animal's skin but also in the laboratory materials. When they constructed a system that also embedded the mirror-mimicking layout, they could enhance further the colour depth through light scattering through and off the granules. The team suggests that this phenomenon might be used in on functional materials, such as light-trapping panels for photovoltaic solar cells.

Fashionable technology

The fibres are rather visually appealing in an aesthetic sense and so might be used by textile makers, fashion designers, and perhaps even artists. Of course, at the intersection of those disciplines, lies the potential for weaving such fibres into the very fabric of wearable technology. Such technology might exploit the optical properties for a new "look" but could also be used for military camouflaging perhaps. Indeed, the Northeastern team collaborated with the US Army Natick Soldier Research, Development, and Engineering Center on the research.

"For more than a decade, scientists and engineers have been trying to replicate this process and build these devices that can colour match, colour change, and camouflage just like the cephalopods, but many of them come nowhere near the speed or dynamic range of colour that the animals can display," Deravi explains. "Cephalopods have evolved to incorporate these specific pigment granules for a reason, and we're starting to piece together what that reason is."

Related Links

Adv Opt Mater 2018, online: "Natural Light-Scattering Nanoparticles Enable Visible through Short-Wave Infrared Color Modulation"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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