Solar stills have been around for a long time. These devices use the sun’s heat to evaporate water, leaving salt, bacteria, and dirt behind. Then, the water vapor cools and returns to a liquid state, at which point it’s collected in a clean container.

The technique has many advantages. It’s simple, and the power source—the sun—is available just about everywhere. But unfortunately, even the latest solar still models are somewhat inefficient at vaporizing water.

Gan’s team addressed this challenge through a neat, counterintuitive trick: They increased the efficiency of their evaporation system by cooling it down.

A central component of their technology is a sheet of carbon-dipped paper that they folded into an upside-down "V" shape, like the roof of a birdhouse. The bottom edges of the paper hang in a pool of water, soaking up the fluid like a napkin. At the same time, the carbon coating absorbs solar energy and transforms it into heat for evaporation.

More information about this fascinating device and some high definition photos can be found on the full Futurity article available online.