New heat-regulating fabric feels fluffy like cotton—but doesn't get wet

Once cotton gets wet, it pulls heat from your body. This is helpful when you're exercising or outside on a hot day, but dangerous in the bitter cold. Now, researchers reporting in ACS Energy Letters have created an ultralight synthetic fiber material with cotton-like fluffiness that also repels water. The prototype fabric outperformed regular cotton in both retaining heat in the cold and releasing heat at room temperature.