On a hot day, a car roof gets so scorching you can't touch it. Usually, cooling a surface requires air conditioning or at least some shade. But there are materials that cool themselves by simply reflecting sunlight and radiating heat into space. The problem is that such coatings are hard to apply quickly and onto uneven objects.
A new method, called solution blow spinning, solves this. Instead of a slow process requiring electricity, a stream of air pulls fibers from a solution, like spinning a web. The application speed is 8–12 times higher, and no conductive substrate is needed. The result is a porous membrane made of polymer with added yttrium oxide nanoparticles. It reflects sunlight and emits heat as infrared radiation, lowering temperatures by 7 degrees below ambient.
The best part: the material is fully recyclable. The membrane can be dissolved, purified, and remade. This paves the way for cheap, eco-friendly cooling of buildings, cars, and even clothing without energy costs.
The yttrium oxide added to the membrane is the same material used in the phosphors of old TV screens.