WHY THIS MATTERS IN BRIEF
We already have invisibility cloaks thanks to metamaterials, and now phase change materials will hide you from infra red sensors to turn you completely invisible.
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If you don’t want to be found then there’s good news for you. Recently I showed off the world’s first real invisibility cloak, and now, in an effort to create the ultimate cloaking device researchers at the University of California San Diego have announced they’ve “developed a wearable technology that can hide its wearer from heat-detecting sensors such as night vision goggles,” even when the ambient temperature of the environment they’re in changes. In short not only could you make yourself invisible from people but now you could hide your heat signature aswell.
The battery powered device, which can be embedded into any fabric and controlled by a wireless circuit board, has a surface that can quickly cool down or heat up in order to match the ambient temperature, thereby camouflaging the wearer’s body heat, and thereby them, from anyone who wants to find them, and it’s surface can go from 10 to 38C, or 50 to 100F, in less than a minute while the inside of it remains comfortable cool.
In order to build the device the team used a phase-changing material that’s similar to wax but with more complex properties. The melting point of the material is 30C, or 86F, the same temperature as the surface temperature of human skin, and if the temperature on the outside of it is higher than that then the material will melt and stabilise, insulating the wearer, and if it’s colder it’ll slowly solidify, still acting as an insulating layer.
The team, led by UC San Diego mechanical and aerospace engineering professor Renkun Chen, detailed their work in a recent issue of the journal Advanced Functional Materials.
At the core of the device though are materials that can create heating or cooling effects when the ambient temperature changes, and flexible electronics that can be embedded into clothing. The outside layer of the device is driven by a technology that Chen and colleagues detailed in a paper in Science Advances made of thermoelectric alloys — materials that use electricity to create a temperature difference — sandwiched between stretchy elastomer sheets, and the device can physically cool or heat itself to a temperature that the wearer chooses.
Current state of the art heat stealth technology consists of a surface coating that changes how much heat clothing emits at the surface. The coating absorbs the heat from the wearer’s body and reflects only enough energy to match the ambient temperature. However, the coating only works at a predetermined temperature so if the ambient temperature rises or falls it no longer works so the teams new device is a breakthrough in camouflage technology. And you can probably guess where it will end up going…
Now though the researchers’ biggest challenge is to scale it up and their ultimate ambition is to create a jacket with it, but under current conditions the garment would weigh 2 kilograms or 4.5 lbs, be about 5 millimeters thick and only function for one hour, so the team will be looking to find lighter, thinner materials so it could weigh two or three times less.
