It could be the perfect answer for people who fight over the thermostat in the office or at home.
Scientists have created an armband which works as a ‘personal thermostat’ to keep people who are always warm or cold at a constant temperature.
The patch inside works for more than eight hours and can lower someone’s skin temperature by up to 10C (50F).
Its inventors say it is a simpler solution than central heating or air conditioning, which have to change the temperature of an entire building to keep a few people comfortable.
That creates arguments when one person who is always cold turns the thermostat up, leaving others sweating.
The armband works using thermoelectric alloys – materials which use electricity to create a temperature difference – sandwiched between heat-conducting stretchy sheets and connected to a small battery pack.
Tested on one person at background temperatures ranging from 22 to 36C (72 to 97F), it stayed at a constant 32C (90F).
Professor Chen, who led the study from the University of California San Diego, said: ‘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.
‘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.’
More than 10 per cent of the energy consumed globally goes on heating and cooling buildings, which makes a personal thermostat the holy grail.
But the options for this are few, including clothes with built-in fans or bulky vests with circulating coolant and water packs.
Researchers built their patch by taking small pillars of thermoelectric materials, soldering them to thin copper strips of electrodes and putting them between the two stretchy elastomer sheets.
An electric current from the battery moves across the pillars, driving heat from one sheet to the other.
If the heat goes to the sheet closest to someone’s skin, they warm up. If it is transferred to the sheet furthest away, warmth is removed from their skin and they cool down.
The flexible, lightweight square-shaped patch is five centimetres (two inches) in diameter.
The researchers, writing in the journal Science Advances, estimate about 100 of them are needed in a vest to cover parts of the body like the back and neck which are at risk of overheating or getting cold.
This would use an estimated 26 watts of power on a hot day, which is less than half of what a laptop needs. However it would still cost hundreds of pounds to manufacture – a cost which researchers hope they can bring down with further research.
On a male volunteer, the patch achieved its target temperature in two minutes and stayed there. It is hoped to be available commercially in a few years.
Professor Chen said: ‘We’ve solved the fundamental problems, now we’re tackling the big engineering issues – the electronics, hardware, and developing a mobile app to control the temperature.’