Wear a patch, get your personal thermostat

■ The goal is to combine patches for smart clothing

Los Angeles, May 19: Scientists have developed a soft wearable patch that cools or warms a user’s skin to a comfortable temperature, an advance that may help save energy on air conditioning and heating.

The device is powered by a flexible, stretchable battery pack and can be embedded in clothing. It could provide personalised cooling and heating at home, work, or on the go, researchers said.

The soft, stretchy patch cools or warms a user’s skin to a comfortable temperature and keeps it there as the ambient temperature changes.

“This type of device can improve your personal thermal comfort whether you are commuting on a hot day or feeling too cold in your office,” said Renkun Chen, a professor at University of California (UC) San Diego who led the study.

“If wearing this device can make you feel comfortable within a wider temperature range, you won’t need to turn down the thermostat as much in the summer or crank up the heat as much in the winter,” Chen said.

Keeping a building’s set temperature 12 degrees higher during the summer, for example, could cut cooling costs by about 70 per cent, he said in a statement.

There are a variety of personal cooling and heating devices on the market, but they are not the most convenient to wear or carry around. Some use a fan, and some need to be soaked or filled with fluid such as water.

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 device physically cools or heats the skin to a temperature that the wearer chooses.

“You could place this on spots that tend to warm up or cool down faster than the rest of the body, such as the back, neck, feet or arms, in order to stay comfortable when it gets too hot or cold,” said Sahngki Hong, a UC San Diego who worked on the project as a PhD student in Chen’s lab.

The researchers embedded a prototype of the patch into a mesh armband and tested it on a male subject. Tests were performed in a temperature-controlled environment.

In two minutes, the patch cooled the tester’s skin to a set temperature of 32°C. It kept the tester’s skin at that temperature as the ambient temperature was varied between 22°C and 36°C.

The ultimate goal is to combine multiple patches together to create smart clothing that can be worn for personalised cooling and heating. So engineers designed a soft electronic patch that can stretch, bend and twist without compromising its electronic function.

The team is now working on patches that could be built into a prototype cooling and heating vest. They hope to commercialise the technology in a few years.

■ The patch is made of thermoelectric alloys — materials that use electricity to create a temperature difference and vice versa — sandwiched between stretchy elastomer sheets.