By Josh Perry, Editor
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Engineers from the University of California San Diego designed a flexible, lightweight wearable patch that cools or heats the skin to maintain a comfortable temperature despite changes to the ambient environment, according to a report from the school.

Prototype of the cooling and heating patch embedded in a mesh armband.
(David Baillot/UC San Diego Jacobs School of Engineering)

The proof-of-concept has a stretchable battery pack and can also be embedded in clothing, according to the article. Researchers believe this could save on energy costs, as users would not need to spend as much on home heating or cooling.

“The patch is made of thermoelectric alloys—materials that use electricity to create a temperature difference and vice versa—sandwiched between stretchy elastomer sheets,” the article explained. “The device physically cools or heats the skin to a temperature that the wearer chooses.”

In lab experiments with the patch embedded into a mesh armband, the device took two minutes to cool the skin to 89.6°F. That temperature was maintained even as the ambient fluctuated between 71.6-96.8°F.

“The researchers built the patch by taking small pillars of thermoelectric materials (made of bismuth telluride alloys), soldering them to thin copper electrode strips, and sandwiching them between two elastomer sheets,” the article continued.

The elastomer sheets were composed of a mixture of Ecoflex and aluminum nitride powder. They were designed to conduct heat and to be flexible. An electric current moved from one sheet to the other, pulling heat along with it, making one side of the patch warm and the other cool. Depending on the flow of the current, the sheet nearest the skin can warm up or cool down.

Researchers create a patch that was 5 cm by 5 cm and uses 0.2 W of power. They estimate it would require 144 patches and 26 W to keep an individual cool on a hot day, but this is far less than the tens of kilowatts that a conventional air conditioning system in an office would require.

The research was recently published in Science Advances. The abstract stated:

“Thermoregulation has substantial implications for energy consumption and human comfort and health. However, cooling technology has remained largely unchanged for more than a century and still relies on cooling the entire space regardless of the number of occupants. Personalized thermoregulation by thermoelectric devices (TEDs) can markedly reduce the cooling volume and meet individual cooling needs but has yet to be realized because of the lack of flexible TEDs with sustainable high cooling performance.

“Here, we demonstrate a wearable TED that can deliver more than 10°C cooling effect with a high coefficient of performance (COP > 1.5). Our TED is the first to achieve long-term active cooling with high flexibility, due to a novel design of double elastomer layers and high-ZT rigid TE pillars.

“Thermoregulation based on these devices may enable a shift from centralized cooling toward personalized cooling with the benefits of substantially lower energy consumption and improved human comfort.”