Seawater can now be desalted without leaving toxic brine behind and while recovering lithium in the process. A research team at the University of Rochester demonstrated this using laser-etched metal panels that exploit an everyday physics effect observed in coffee cups. Nearly 100 percent of dissolved salts are collected as solids, no liquid waste. Results appeared May 31, 2026, in the journal Light: Science & Applications.
Seawater desalination and the brine problem
Conventional seawater desalination relies primarily on reverse osmosis: water is pushed under high pressure through membranes that retain salts. The process is energy-intensive, requiring 4 to 6 kilowatt-hours per cubic meter, and produces concentrated brine as waste. Globally, about 150 million cubic meters of this brine are generated daily and discharged into seas and coastal waters. For comparison: all German rivers combined carry less than 100 cubic kilometers annually. The salt concentration in brine is roughly double that of normal seawater. In enclosed bodies like the Persian Gulf, this damages marine ecosystems through elevated salinity and oxygen depletion.
Solar-based approaches are theoretically attractive: no grid power needed, no chemicals. Yet they have failed at a structural problem. When water evaporates under sunlight, salts crystallize on the collector surface. After days, the surface crusts so heavily that performance collapses.
The coffee-ring effect as unexpected solution
Professor Chunlei Guo's team at the University of Rochester Laboratory for Laser Energetics exploited a everyday physics effect: the coffee-ring effect. When a coffee stain dries, deposits gather at the edge, not the center. The reason: evaporation transports liquid outward, carrying dissolved particles along.
The researchers applied this principle to metal panels engraved with femtosecond lasers. The microstructures make the metal deep black and strongly water-attracting. The panel is divided into two zones: an active middle zone where water evaporates, and a passive edge zone where salts collect without blocking the evaporation surface. The result is nearly 100 percent of dissolved salts as solid form, no liquid waste.
What the laser plates deliver
The system was tested with water samples from the Pacific, Atlantic, and Indian Oceans. It requires no chemical pretreatment and operates without external power supply. A second study in the Journal of Materials Chemistry A shows that roughly 50 percent of lithium in the salt residue can be recovered using hydrogen titanate nanoparticles. This matters because lithium is critical for batteries and is currently extracted laboriously from salt lakes or hard rock.
The project is funded by the National Science Foundation, the Bill and Melinda Gates Foundation, and the Worldwide Universities Network. The Gates Foundation involvement signals priority: the foundation specifically funds technologies for water-scarce regions without stable power infrastructure.
In comparison: two approaches, one goal
In parallel, a team at South Korea's Ulsan National Institute of Science and Technology (UNIST) is pursuing a different approach. Professor Ji-Hyun Jang published a solar evaporator system in Advanced Materials in December 2025 using a special oxide material called CuMnCrO4 that absorbs 97.2 percent of sunlight from ultraviolet to near-infrared. A one-square-meter unit produces 4.1 liters of clean water per hour, seven times faster than natural seawater evaporation. The UNIST system also prevents salt crusting through special construction with water-attracting fibers.
Both approaches share the goal of brine-free desalination but differ fundamentally in materials science: Rochester uses laser-structured metal and exploits the coffee-ring effect for salt separation. UNIST relies on chemically optimized oxide material with broad light absorption. Which approach suits industrial scale remains open.
Compared to established reverse osmosis, neither method offers direct throughput advantage. Large reverse osmosis plants produce hundreds of thousands of cubic meters of drinking water daily on relatively small footprints. Solarthermal systems need sunlight and area on a scale limited in densely populated coastal regions. Their advantage lies elsewhere: they could function without infrastructure and grid power in remote regions lacking large desalination plants.
From the lab to 785 million people without drinking water
785 million people globally lack access to basic water services, according to UN data. Four billion experience water shortage for at least one month yearly. Both technologies currently exist at lab and prototype stage. Scaling to field deployment requires three hurdles: expanding panel area beyond square meters, reducing manufacturing costs for specialty materials, and integration into off-grid supply systems.
A single square meter of panel producing liters of daily drinking water meets one person's needs. For small villages without water supply in coastal North Africa, Southeast Asia, or Pacific island states, even multiples would be feasible. Whether the path forward lies in Rochester's cost reduction of laser manufacturing or UNIST's mass production of CuMnCrO4 material is the crucial open question.