Radiative cooling is the natural process through which objects shed heat in the form of infrared (IR) radiation. All material ... s at room temperature emit infrared at wavelengths of 5–15 μm. However, the process is typically not very efficient because it is counteracted by external influences that heat the object, such as sunlight and air currents. Air, meanwhile, absorbs and emits very little radiation with wavelengths 8–13 μm. The Earth cools itself at night by emitting infrared through this “atmospheric window” into space. After receiving a $3M federal grant from the US Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) in 2015, a team at the University of Colorado Boulder (CU-Boulder) in the US developed a new metamaterial film that provides cooling without needing a power input. Made out of glass microspheres, polymer and silver, the material uses passive radiative cooling to dissipate heat from the object it covers. It emits the energy as infrared radiation and also reflects solar light. Most importantly, the material can be scalably manufactured at low-cost through roll-to-roll manufacturing processes. read more