Solar stills use the sun to evaporate dirty or salty water and condense the vapour into safe drinking water, but large expensive stills can only produce enough water for a family.

However, researchers have now developed a new material that speeds the process of evaporation and thus enables small stills to provide the entire water requirements of a family.

If the tech could prove cheap enough, it could provide an answer to the growing water crisis and give access to clean water to millions of impoverished people around the world.

Guihua Yu, a materials scientist at the University of Texas in Austin, and colleagues has found a way around this limitation.

Their method involves hydrogels, polymer mixtures and a water-absorbent polymer called polyvinyl alcohol. It also has a light absorber called polypyrrole (PPy)—which they placed atop the water’s surface in a solar still.

According to the report published in Science Advances, the mechanism of the apparatus sees the water molecules inside the gel being bonded tightly to the PVA, each forming multiple chemical links known as hydrogen bonds.

With most of their bonding ability tied up to the PVA, the bound water molecules manage to only loosely bind with other water molecules and share fewer bonds with their neighbours, thus creating 'intermediate water' that evaporates faster and more readily than regular water.

On evaporation, they are immediately replaced by other water molecules in the still.

Yu's technology saw double the theoritical limit of water being produced using the apparatus.

Yu and his colleagues have also managed to mix in a third polymer, called chitosan, which also strongly attracts water.

Adding chitosan to the mix created a gel that could hold even more water and increased the amount of intermediate water as a result, thus produced almost 12 times the amount produced by today's commercially available versions. The results of the study were reported in Science Advances.