T-shirt keeps wearers both cool and warm

Researchers have developed a sustainable fabric that can cool off and warm up the wearer, depending on which side is worn facing out

Spotted: We’ve all done it – dressed for one temperature, only to find the weather changing mid-afternoon and instantly regretting our choice of clothing. As weather patterns become more unpredictable in the wake of global warming, this is likely to happen more and more. However, a team of Chinese researchers may be able to help. They have developed a fabric, dubbed Janus, that can both cool the wearer down and warm them up.

The t-shirt was created by layering polymer and cotton fibres with materials that absorb or reflect solar energy. On the warm side, the material is covered in zinc and copper nanoparticles, which absorb solar energy to provide heat. On the cool side, the fabric is covered with a very thin layer of aluminium, that reflects solar energy to cool the wearer down. This layer is also porous, to allow body heat to escape.

Wear the t-shirt one way, and it will keep you 11 degrees cooler than a comparable plain white cotton t-shirt. Flip it around, and it will keep you 14 degrees warmer than a plain black cotton shirt. On top of this, the researchers embedded a thermoelectric generator inside the fabric. This harvests energy from the temperature differential between the hot and cold side of the t-shirt. The power generated can be used to power small sensors.

In their paper, published in Nano Letters, the research team describes the shirt as useful for dealing with the many challenges of “personal thermal management.” They also claim “the eco-friendly passive nanostructured textile which harvests energy from the sun and the outer space” can help in providing optimal localised heating and cooling.

Technical fabrics like Janus are becoming not only more popular, but more technical too. At Springwise, we have seen innovations in this space develop a range of new fabrics, including a breathable fabric made from recycled plastic and a hemp-based fur that mimics the structure of animal-based fur, without the cruelty.

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