New heat-regulating fabric feels fluffy like cotton—but doesn't get wet (opens in new tab)

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.