When we are out in cold weather, we wear warm clothes to stay comfortable. But there is a snag. Regular warm clothing can’t adjust to changes in our body temperature. If we start to sweat, we get too hot and sticky, which makes us want to remove layers. This defeats the purpose of wearing them, since we still need to stay warm.

But what if our clothes could adapt? That’s the question Xiuqiang Li at Nanjing University of Aeronautics and Astronautics in China and his colleagues set out to answer. They have developed a jacket with a filling made from a bacterial cellulose membrane that responds to human sweating.

The innovative membrane automatically adjusts its thickness based on humidity. It’s 13 millimeters thick in cool, dry conditions and shrinks to just 2 millimeters when humidity levels are high, such as when you sweat. This allows the jacket to be thick when you need to stay warm and then get thinner when you want to cool down a little.