Scientists developed a new type of water purifier powered by sunlight that solves a major problem with previous solar water purifiers: salt buildup. The innovation uses special light-sensitive materials that change how they interact with water depending on whether it’s sunny or dark. When salt builds up on the surface in the dark, the material becomes more water-loving and washes away the salt. When the sun shines, it becomes water-resistant again, focusing on pure water production. This smart material could help provide clean drinking water in coastal regions and reduce reliance on traditional energy-intensive desalination methods.