According to the World Wildlife Fund, some 1.1 billion people around the world do not have access to safe drinking water. To address this issue, scientists from the University of Princeton have developed an affordable solar panel water purifier that’s inspired by the pufferfish’s ability to absorb water.

Resembling a large sponge, the solar-powered hydrogel device soaks up water while leaving contaminants behind. To collect the filtered water, the user only has to place the saturated sponge in the sun. The water-filtration process was inspired by the pufferfish, which takes water in when it’s threatened and releases it once the danger is gone.

“To me, the most exciting thing about this work is it can operate completely off-grid, at both large and small scales,” said Rodney Priestley, the device’s co-inventor. “It could also work in the developed world at sites where low-cost, non-powered water purification is needed,” he added.

The gel-based sponge can be placed in a water source in the evening and then placed under the sun during the day to release the water. The device is able to filter out petroleum and other oils out of the water, get rid of metals like lead, and filter out pathogens like yeast.

The process works thanks to the hydrogel’s ability to change properties in different temperatures. Simply put, at room temperature, the gel acts as a sponge soaking up water. But when the temperature reaches 33C (91F), the gel changes its properties to repel water molecules, thus releasing the liquid.

The research team is now exploring ways to make the technology widely available, hoping that the low-cost, off-the-grid water purification system could soon provide clean drinking water to communities worldwide.