To mimic the zebrafish, Rossiter and Conn constructed an artificial ink cell by mounting a flat, oval-shaped silicone display chamber between two glass microscope slides. They used a thin tube to connect a well of black ink to the display chamber; when the researchers gave the command, a small pump pushed the black fluid into the transparent chamber, turning it from clear to an opaque black. To reverse the effect, the researchers turned on a second pump, which sent a supply of clear liquid into the chamber and pushed the black fluid back into its reservoir. (The organic clear fluid and the black water-based ink do not mix.)
Just like in nature, the zebrafish-inspired chromataphores work more slowly than those modelled on the cuttlefish, but the final effect is dramatic. In just a few seconds, the transparent display chamber turns a rich, dark black.
The next step, Rossiter says, is to refine the bio-inspired chromataphores and to network more and more of them together. “We’ll put these things together to produce larger arrays and at the same time we’ll miniaturise them,” he says. By layering different chromatophores and pigment cells, engineers could create a soft material capable of a variety of sophisticated effects, including multiple colour changes and moving patterns that appear to ripple across the fabric.
Such colour-changing materials have obvious military applications, allowing soldiers to blend into different environments with the flick of a switch. But, Rossiter points out, we could also use such clothing to make ourselves more conspicuous. “In modern society,” he says, “you may want to display yourself.” Imagine, for instance, a shirt that turns bright orange when you’re walking or biking along a heavily trafficked road. Or a jacket that can flash bright colours if you get lost in the woods, making it easier for search parties to spot you.
For his part, Rossiter imagines teens coveting cuttlefish-inspired clothing simply for fun and fashion. They could even go out to a nightclub and put on colour-changing displays to impress potential mates, just like their cephalopod cousins.