Reversible fabric capable of keeping wearer cool or warm

Reversible fabric can serve as personal air conditioning or heater

Image credit: Yi Cui Group

Materials scientists at Stanford University have developed a reversible fabric that – with no energy consumption – can keep the wearer cool or warm depending on which way round it is worn.

This project was inspired by the theory that, if people could wear clothing that allowed them to be comfortable under a range of weather conditions, they would be able to lower their energy consumption and save money by disposing with inefficient central heating and air conditioning systems.

It is estimated that 13 per cent of all energy consumed in the US is dedicated to central heating and air conditioning, but turning a thermostat down just 1°C can save a building ten per cent of its heating energy; the reverse is true for air conditioning. Reducing the necessity of indoor temperature control could significantly cut a country’s energy consumption.

Human bodies are already adept at controlling our body temperatures to a certain extent by shivering, sweating and causing our bodily hair to stand on end. Pulling on insulating woolly layers or breathable, loosely-fitted clothing can make us more comfortable. However, through much of the year, we rely on indoor temperature control.

“Why do you need to cool and heat the whole building? Why don’t you cool and heat individual people?” said Professor Yi Cui professor of materials science and engineering at Stanford University.

Previously, Professor Cui’s team had developed a highly breathable fabric inspired by cling film which allows infrared radiation emitted by the body to pass through it, cooling the skin. This fabric was opaque, and capable of keeping skin cooler than cotton by 2°C in laboratory tests.

Curious to see if they could make this process worth the other way around, the researchers stacked two layers of material with different abilities to release heat energy, and placed a layer of their cooling synthetic fabric on either side. On one side of the white fabric, a thin coating of copper traps heat between the fabric and skin, while on the other, a carbon coating releases heat from beneath the fabric.

Wearing the layers of material with the copper coating facing outwards traps heat, keeping the wearer warm, while wearing the carbon coating on the outside releases heat, keeping the wearer cool. This increases the range of comfortable temperatures to such an extent that in moderate climates, air conditioning and central heating could be rendered unnecessary.

“Ideally, when we get to the stuff you want to wear on skin, we’ll need to make it into a fibre woven structure,” said Professor Cui. A woven version of this fabric would be stronger, more elastic, comfortable, aesthetically appealing, and potentially machine washable, making it an attractive alternative to indoor temperature control.

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