Engineer Alon Gorodetsky remembers the precise moment he decided to drop everything and start studying cephalopods. This class of sea animals includes squid, cuttlefish and octopuses.
“I saw this amazing video by (a biologist named) Roger Hanlon of an octopus suddenly appearing out of an algae-covered rock,” Gorodetsky says. The amazing now-you-don’t-see-it-now-you-do ability of the animal “made me think, I have to work on this.”
Ever since, Gorodetsky’s lab at the University of California at Irvine has been trying to make what he calls “technologically valuable things” based on cephalopods’ camouflaging skills. They’ve finally succeeded in creating a material that will let people, not disguise themselves as rocks and algae, but regulate how warm or cool they feel. The UCI team built this material using biomimicry — watching how a biological organism behaves, then imitating it.
Cephalopods have a layer of skin that’s packed with pigment-containing cells called chromatophores. When you can’t see the cephalopod, it’s expanding and contracting its chromatophores between little upright points and big, flat disks. Think about drawing dots on a piece of plastic wrap, says Gorodetsky, then stretching the plastic so that those dots get much bigger.
In the case of the cephalopod, that action changes how light is reflected off its skin. This lets it change its appearance. The UCI team used it as inspiration to lay little pieces of copper tightly together on top of a rubber sheet. When the sheet is relaxed, the copper absorbs and retains heat. When the sheet is stretched, the copper pieces are pulled apart so that spaces appear between them. Heat then escapes from those spaces.
A simple process
It’s a simple process that could let people change their own temperature rather than the temperature of a room they’re sitting in — Gorodetsky imagines how this could help buildings save money and energy on heating and cooling. He points out that no two people experience hot and cold the same. His team highlighted this in a demonstration.
“We made sleeves from the material and had three people wear them,” he says. “One person’s arm started sweating uncontrollably,” so they simply stretched the sleeve to feel relief. “One person was fine. A third person felt cold” and could put on an extra sweater rather than turning up the thermostat.
In addition to cephalopods, inspiration for the material was from the original thin, metal-coated space blanket designed by NASA in the 1960s. It works well in one set of conditions — when you’re cold and need to warm up. But its properties are static, meaning they can’t change as conditions do. UCI’s material is dynamic — able to change to meet shifting needs; it can be stretched thousands of times without losing this ability.
The next step for Gorodetsky and the UCI team is figuring out how to put the material into actual fabric, then to create rolls of it that can be used to fashion shirts, sheets, tents and window coverings.
“There’s a world of applications for this material,” Gorodetsky says. “We just have to convince people to wear it and use it.”