Scientists have developed a new solar-powered desalination system that converts seawater into fresh water while removing nearly all the salt as a solid rather than creating harmful brine. This self-cleaning technology also has the potential to recover valuable minerals like lithium from the desalination waste, turning what was once considered waste into a useful resource. Around the world, billions of people still lack access to safe drinking water. The United Nations estimates that 2.2 billion people do not have safely managed drinking water, and regions from California to the Middle East increasingly rely on desalination plants to convert seawater into fresh water. While desalination is a critical water source, current methods like reverse osmosis and thermal distillation often require significant energy, chemical treatments, and produce concentrated brine, which can harm marine life when released into the ocean. Researchers at the University of Rochester have developed a new approach that could address several of these issues. The system, described in a study published in Light: Science & Applications, uses solar thermal desalination. It is led by Chunlei Guo, a professor of optics and physics at the university. At the heart of the technology are solar panels made from black metal treated with ultrafast lasers. These lasers create microscopic structures on the metal surface that enhance its ability to absorb sunlight and cause water to spread across the surface rather than bead up. The panels are designed to draw a thin layer of seawater across their surface, where the sunlight heats and evaporates the water, leaving behind salts and minerals. The system is designed to move these minerals away from the area where evaporation occurs, preventing the buildup of salt that can clog the system. This is a significant improvement over previous solar desalination methods, which often struggled with salt accumulation in real seawater, which contains more complex mixtures of dissolved minerals than artificial seawater used in lab tests. The researchers used a natural physical phenomenon called the "coffee ring effect" to guide the minerals to the edges of the panel, similar to how spilled coffee leaves a dark ring of concentrated particles on a surface. In addition to producing fresh water, the system collects the remaining salts in solid form, which could be valuable resources. For example, lithium, a key component in batteries for electric vehicles and electronics, can be extracted from the leftover salts. In a related study, the team demonstrated that the same panels can be modified to recover lithium from seawater. This innovation could reduce the environmental impact of traditional lithium mining and provide a sustainable way to extract valuable minerals. While the technology is still in the early stages, the researchers believe it has the potential to be scaled up to address both the global need for fresh water and the demand for sustainable mineral resources.