It’s not difficult to see why people think the squiggly uprising is upon us. Apart from being ludicrously intelligent and incredibly adaptable, a number of cephalopods are also able to change color, which gives them remarkable camouflage abilities.
Inspired by such sneaky huge-changing shenanigans, a team from the University of California, Irvine (UCI) has manufactured their very own camouflage device. No, it’s not quite the Invisibility Cloak from Harry Potter, but to infrared (heat-seeking) scanners, using this material will make you appear to disappear, just like an octopus slipping out of sight on the seafloor.
The quite literal nature of the beast is brought up early on in the team’s Science paper, delineating how a color-changing squid, for example, is able to use its skin’s sophisticated architecture to both become practically invisible, as well as signal its compatriots.
Such critters possess both color-generating chromatophore pigment cells and light-reflecting iridocyte cells. The former are expanded and contracted on timescales of hundreds of milliseconds, allowing them to function as filters that absorb and reflect specific wavelengths of visible light. The latter, which take tens of seconds to morph, change how light is bent through them.
The combination of both gives these cephalopods what the team refers to as a “dynamic bioelectronic display,” one which has inspired plenty of artificial, optics-based contraptions. Camouflage is no different, but so far, nature’s pipped us to the post, and bioengineering has come up short. This research team hoped to change that – at least, for part of the electromagnetic spectrum.
This type of color-changing ability can be mimicked using an elastomer membrane sandwiched between electrode panels. Changing the voltage can trigger various physical changes, like the thickness and area of the elastomer. Give the elastomer a pigment, or structures that can alter the passage of light, and boom, you have a fake color-changing beastie.
It’s not that simple, though. Actually making this work effectively and efficiently is mechanically very tricky. The materials often wear down, they only work in specific environments, and they often require a lot of energy to operate.
What we do have now, however, is a relatively effective way to hide from the infrared section of the electromagnetic spectrum. Taking inspiration from these cephalopods, this team's created both artificial chromatophore pigment cells and iridocyte cells and spliced them into a specialized, electrically conductive membrane coated with an infrared-reflecting area.
Depending on what type of electrical current is passed through these membranes, the chromatophores absorb varying amounts of infrared light, and the iridocytes reflect varying amounts of light, both comparable to their living inspiration. Their device ready, they tested its ability to conceal itself from infrared cameras.
When heated by a thermal source, the radiation emitted and reflected by the artificial cephalopod “skin” in its deactivated state allowed infrared cameras to detect it. Upon activation, the skin began to morph, and the pseudo-cells within it began to absorb and reflect the thermal radiation differently.
With just the slightest of electrical and physical changes, its surface temperature was altered by a couple of degrees, and the skin disappeared from view on the thermal cameras.
The applications of such a device are abundantly clear. Security services concealing themselves from heat-seeking cameras – or even weapons – would love to get their hands on this; in more benign arenas, this skin could help reduce wasteful heat loss from buildings.
For those pining for a true Invisibility Cloak, don’t fret. The study notes that, although this applies to infrared for now, “in principle they could be adapted for functionality within the visible” region of the electromagnetic spectrum.
Senior author Alon Gorodetsky, an assistant professor at UCI’s Department of Chemistry, confirmed to IFLScience that “we are pursuing both autonomous thermoregulatory technologies and adaptive camouflage that function in the visible as our next steps.”
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