A research team at University of Rochester developed a solar-powered method that extracts drinking water from real seawater without generating brine. The study was published May 27, 2026, in the journal Light: Science & Applications.
Two-thirds of world population faces water scarcity
According to the study authors, globally growing freshwater demand coupled with declining natural supply leaves two-thirds of the world population facing severe water scarcity. According to UN estimates, 2.2 billion people lack access to safely managed drinking water supplies. Communities from California to the Middle East depend on desalination plants for freshwater. Common methods like reverse osmosis and thermal distillation are energy-intensive, require water pre- and post-treatment, and leave concentrated brine that harms marine life when returned to the sea because it increases salinity and lowers oxygen levels.
How the black metal panel pulls water and sorts salt
Using femtosecond laser processing, researchers created a superwicking black metal panel (SWBM) that pulls a thin water film upward across its surface, absorbs nearly all solar radiation, and self-directs crystallized salts from active to passive regions for self-cleaning. According to the authors, the panels are created in a single processing step from thin aluminum foil of 200 micrometers, with four variants produced using different laser powers and groove depths between approximately 80 and 150 micrometers. At 1.2 watts laser power, the surface achieved approximately 98 percent solar absorption at maximum radiation and approximately 92 percent across the full solar spectrum. The strongest capillary-action sample pumped water upward at an initial velocity of 8 centimeters per second.
Self-cleaning relies on the so-called coffee ring effect and salt creep, amplified by deeper and wider grooves. As Guo explained via University of Rochester, "When coffee drops on a surface, water eventually evaporates and leaves a ring of concentrated coffee particles at the outer edge. We use the same principle to transport salts to the passive region."
According to Guo, other researchers' solar-thermal desalination techniques work well in laboratory tests using simulated seawater with only water and sodium chloride because salt crystallizes into granular, porous form. Real seawater contains magnesium and calcium compounds that crystallize into crust-like, non-porous form and clog the surface. To prevent this, Guo's team etched grooves in the black metal with such precision that salts and minerals from real seawater simply fall away.
One week continuous operation without maintenance
In testing, the system tracked the sun and continuously treated real seawater for one week without maintenance. Average evaporation rate was 1.76 ± 0.04 kilograms per square meter per hour, corresponding to approximately 74 percent evaporation efficiency, while salt recovery rate reached 61.74 ± 2.46 grams per square meter per hour, representing nearly 100 percent salt extraction. In a separate two-hour test under simple sun exposure, two tested panel variants remained consistently clean and achieved stable evaporation rates of approximately 1.84 and 1.70 kilograms per square meter per hour, while a weaker-processed sample showed a decline in initial evaporation rate of more than 45 percent within two hours because its surface was covered with salt crystals.
Compared to reverse osmosis and multi-effect distillation
According to the study, widely used reverse osmosis and multi-effect distillation methods achieve recovery rates of 0.42 and 0.22 respectively and generate 0.6 to 6.7 kilograms of CO2 per cubic meter of desalted seawater. Due to low recovery rates, these systems discharge 58 to 78 percent of incoming water as waste brine into bodies of water like lakes, rivers, or coastal areas, underground injection, or land application. An ideal process would achieve zero brine discharge, commonly termed Zero Liquid Discharge (ZLD), where solid salts remain as byproduct instead of liquid waste, exactly targeting the researchers' new method.
Salt as raw material: lithium extraction is also possible
According to the study, seawater contains vast quantities of valuable minerals, hundreds of times more than on land, many of which are scarce and high-value. In a related publication in Journal of Materials Chemistry A, Guo and colleagues demonstrated how to separate lithium from other salts using the same panels by embedding hydrogen titanate nanoparticles into the metal surface grooves. Using water samples from the Great Salt Lake, researchers extracted approximately 50 percent of lithium from the salts remaining after desalination. "Mining lithium from the earth has proven very burdensome for energy and environment, so direct extraction from salt water could be a very important future path," Guo said. This lithium test derives from a separate experiment using Great Salt Lake water and a separate publication, not from the seawater system itself described here.
Tested only at small scale so far
According to Guo, the superwicking desalination technology has so far only been demonstrated in proof-of-concept experiments at small-scale laboratory devices. He nonetheless considers it fundamentally scalable and sees potential to improve global access to drinking water and build more sustainable supply chains for valuable minerals. The research was supported by the National Science Foundation, the Bill & Melinda Gates Foundation, and the Worldwide Universities Network. Whether the laboratory success leads to a facility actually contributing to global water supply remains open, as the technology has only been tested at small-scale proof-of-concept levels according to Guo.