Person wearing a prototype cooling and heating patch embedded in a mesh armband.

A battery-powered cooling device can be embedded in a flexible armband. Credit: David Baillot/Jacobs School of Engineering, Univ. California, San Diego

Materials science

Air conditioner ‘in a patch’ provides portable cooling

Device exploits semiconductors to whisk heat away from a polymer skin patch.

Personal cooling could be one step closer to reality, thanks to the advent of a flexible cooling device that can be incorporated into clothing.

Thermoelectric systems use semiconductors to pump heat from one side of a device to the other, creating a cool zone and a hot zone. Such systems can provide compact, easily adjustable cooling, but getting them to efficiently dissipate heat has proved challenging.

Renkun Chen, Sheng Xu and their colleagues at the University of California, San Diego, addressed this problem by embedding multiple pillars of a semiconducting material between two stretchy polymer sheets. One sheet served as the hot zone, the other as the cool zone. This design conferred flexibility and insulated the hot and cold sides from each other, allowing the hot layer to dissipate its heat into the air.

The team added a flexible battery pack to the design, creating a patch that can cool skin temperature by more than 10ºC. The use of such devices could reduce the demand for energy to power central air conditioning by 20% in typical buildings, and enhance a wearer’s comfort outdoors, the authors say.