Seawater can be desalinated without leaving behind toxic brine and meanwhile recover lithium. A research team at the University of Rochester demonstrated this with laser-engraved metal panels exploiting a physical everyday effect observed in your coffee cup. Nearly 100 percent of dissolved salts are captured as solids, no liquid waste. Results appeared May 31, 2026 in the journal Light: Science and Applications.
Seawater desalination and the brine problem
Conventional seawater desalination works mainly through reverse osmosis: water is forced through membranes under high pressure that hold back salts. The process is energy intensive, roughly 4 to 6 kilowatt hours per cubic meter, and produces concentrated salt brine as waste. Globally, roughly 150 million cubic meters of this brine are generated daily, discharged into seas and coastal waters. For comparison: all German rivers combined carry less than 100 cubic kilometers annually. Salt concentration in the brine is roughly twice that of normal seawater. In enclosed waters like the Persian Gulf, this damages marine ecosystems through elevated salinity and oxygen depletion.
Solar-based approaches are theoretically more attractive: no grid power needed, no chemicals. Yet so far they failed at a structural problem. Once water evaporates under sunlight, salts crystallize on the collector surface. After a few days the surface is so heavily encrusted performance drops sharply.
The coffee ring effect as unexpected solution
The team led by Professor Chunlei Guo at the University of Rochester's Laboratory for Laser Energetics exploited a physical everyday effect: the coffee ring effect. When a coffee stain dries, deposits accumulate at the edge, not the center. The reason is that evaporation transports liquid outward, carrying dissolved particles along.
The researchers transferred this principle to metal panels engraved with femtosecond lasers. The microstructures make the metal deeply black and highly water-attracting. The panel is divided into two zones: the active zone in the middle evaporates the water. In the passive rim zone salts accumulate without blocking the evaporation surface. The result is nearly 100 percent of dissolved salts in 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 of water and operates without external power. A second study in the Journal of Materials Chemistry A shows roughly 50 percent of contained lithium can be recovered from the salt residue using hydrogen titanate nanoparticles. This matters because lithium is considered a key battery material and currently requires labor-intensive extraction from salt lakes or hardrock mining.
The project receives funding from the National Science Foundation, the Bill and Melinda Gates Foundation, and the Worldwide Universities Network. Gates Foundation involvement signals intentional focus: the foundation specifically finances technologies for water-scarce regions without stable power infrastructure.
In comparison: Two approaches, one goal
Parallel to Rochester, a team at Ulsan National Institute of Science and Technology (UNIST) in South Korea works on a different approach. Professor Ji-Hyun Jang published in December 2025 in Advanced Materials a solar evaporator system with a special oxide material called CuMnCrO4 that absorbs 97.2 percent of sunlight from ultraviolet through near-infrared. A one-square-meter unit thus produces 4.1 liters of clean water hourly, seven times faster than natural seawater evaporation. The UNIST system also prevents salt encrusting through special construction with water-attracting fibers.
Both approaches share the goal of brine-free desalination but differ fundamentally in material technology: Rochester relies on laser-structured metal and uses the coffee ring effect for salt separation. UNIST relies on chemically optimized oxide material with broad absorption range. Which approach suits industrial scales remains open.
Compared to established reverse osmosis, neither procedure offers direct throughput advantage. Large reverse osmosis plants produce hundreds of thousands of cubic meters of drinking water daily on comparatively small footprint. Solar-thermal systems need sunlight and land at scales limited in densely populated coastal regions. Their advantage lies elsewhere: they could function without infrastructure and without grid power in remote regions where large desalination plants don't exist.
From lab to 785 million people without clean water
785 million people worldwide lack access to basic water services according to UN figures. Four billion experience water scarcity at least one month annually. Both technologies currently remain in lab and prototype stage. Until field deployment three hurdles must be overcome: scaling panel area beyond few square meters, reducing manufacturing costs for specialty materials, and integrating into power-free supply systems.
A single square-meter panel producing several liters of drinking water daily suffices for one person's needs. For small communities without water systems in coastal regions of North Africa, Southeast Asia, or Pacific island states, even multiples would be realistically deployable. Whether the path forward runs through cost reduction of laser manufacturing at Rochester or mass production of CuMnCrO4 material at UNIST is the deciding open question.