Drinking Water From the Sea, Without Brine or Chemicals
According to the UN, 2.2 billion people on Earth today lack access to safely managed drinking water. Climate change is making the situation ever more dramatic: in the Mediterranean, falling rainfall and increasingly intense droughts are straining water supplies, while Spain, Cyprus and Malta already rely heavily on turning seawater into freshwater. But conventional desalination methods – reverse osmosis and thermal distillation – come at a serious price: their energy-intensive operation, need for chemical treatment and the ecological burden of the concentrated brine they produce have long been unsolved. With results published in May 2026, researchers at the University of Rochester have shown that these limits can be overcome all at once.
71% of the Earth's surface is water – yet according to the UN, 2.2 billion people today have no access to safe drinking water. Turning seawater into freshwater seems a logical answer, but existing technologies have suffered from two fatal flaws: they guzzle energy, and at the end of the process they pour concentrated brine back into the ocean. In spring 2026, researchers at the University of Rochester presented a system that uses only sunlight, needs neither chemicals nor external energy – and turns the salt into a raw material rather than waste.
When sunlight does the work
At the heart of the system presented by Tang et al. (2026a) in Light: Science & Applications is a special panel: a blackened metal surface treated with a femtosecond laser. This process – using light pulses lasting 10⁻¹⁵ seconds – builds two key properties into the surface at once. The panel absorbs almost all incoming sunlight, and it exerts an extremely strong capillary effect: the researchers describe it as a super-wicking surface.
The wicking effect draws a thin layer of seawater onto the panel's active zone. Heated by sunlight, the layer evaporates, and the vapour condenses into clean, drinkable water. At the same time, dissolved salts and minerals – instead of accumulating on the active surface – migrate to the panel's passive zones, where they are deposited in solid form.
The process is self-regulating: the salts are forced out of the working area, so drinking water is produced continuously without chemical pre-treatment or an external energy source.
The coffee-ring effect as an engineering solution
Treating seawater is a much more complex task than laboratory experiments first suggest. In simplified test water – containing only sodium chloride – salt crystallises in a loose, porous structure through which water can flow. Real ocean water, however, also contains magnesium, calcium and many other minerals: these form a hard, dense crust that eventually blocks the water's path and stops desalination. The phenomenon resembles the way limescale gradually reduces a kettle's efficiency – except that in seawater the mineral concentration is many times that of tap water.
Professor Chunlei Guo's team found the solution to this problem in the well-known coffee-ring effect. They created microscopic grooves on the metal surface that steer the salts towards the passive zone before they can settle.
“If you drop coffee on a surface, eventually the water evaporates and there's a ring left at the outer edge that is the concentrated coffee particles. We use that same principle to advance the salts to the passive region.”
Tests with water from the Pacific, Atlantic and Indian Oceans all confirmed that the surface really does clean itself: fresh water can be extracted continuously while the salts collect in the passive areas.
The brine problem solved
One of the most serious by-products of conventional desalination plants is concentrated brine, which in many cases is discharged straight back into the ocean. This raises the salinity of receiving waters, lowers dissolved oxygen levels and can seriously damage marine ecosystems. In the Mediterranean – where Spain, Greece and the smaller island states operate dozens of desalination plants – brine discharge is already a documented ecological problem.
The Rochester system eliminates this problem at the root: dissolved salts are recovered in solid form, and no brine is produced at all. The recovered materials are not to be treated as waste but as potential raw materials – including for table salt and valuable industrial minerals.
The hidden value of lithium
Perhaps the most surprising chapter of the research concerns lithium extraction. In a related study published in the Journal of Materials Chemistry A, Guo and his team showed that the same super-wicking panels – with a minor modification – can also selectively separate lithium from the other salts (Tang et al., 2026b).
The key to the method is that hydrogen titanate nanoparticles were embedded in the microscopic grooves of the metal surface; they selectively bind lithium ions while letting other minerals pass. In an experiment with water from the Great Salt Lake in Utah, the system recovered almost 50% of the lithium from the salts left after desalination.
“Mining lithium from the Earth has proven to be very taxing from an energy and environmental standpoint, so pulling lithium directly from saltwater could be a very important future route.”
Industrial demand for lithium is unprecedented. Conventional mining – mainly in South America and Australia – comes with a huge ecological burden and local protests. If extracting lithium from seawater or salt lakes becomes feasible at industrial scale, it could fundamentally change the supply chain for critical raw materials.
The European context
On Europe's southern edge, water shortage is everyday reality. According to the European Environment Agency, the Mediterranean is one of the world's most vulnerable regions to water stress: most of Cyprus's drinking water comes from desalination plants, Spain operates hundreds of such facilities, and demand is growing further as the climate changes.
These systems face exactly the pain points the University of Rochester's solution addresses: energy-intensive operation, the cost of chemical pre-treatment and the ecological burden of brine discharge. The Mediterranean's abundant sunshine also creates ideal conditions for solar desalination – if the new system proves workable at industrial scale, the southern EU member states could be natural early adopters of the breakthrough.
A promising innovation
The result of the University of Rochester team – published by Tang et al. (2026a) in Light: Science & Applications and funded by the NSF, the Bill & Melinda Gates Foundation and the Worldwide Universities Network – should for now be considered a laboratory proof of concept. Many engineering and economic questions remain to be answered before industrial use. But the system demonstrated in principle offers something desalination has never offered before: solar-powered, chemical-free and waste-free drinking water production from which lithium and other valuable minerals can also be recovered. Global water scarcity, European water stress and the raw material needs of the energy transition can be connected in a single system – and that intersection is where the real weight of the breakthrough lies.
Researchers at the University of Rochester have developed a solar system with a black metal surface treated by femtosecond laser that turns seawater into drinking water without chemical pre-treatment or toxic brine waste. The super-wicking surface draws a thin layer of seawater onto the active zone, where sunlight evaporates the water, while the salts migrate through microscopic grooves – using the coffee-ring effect – to the passive zone, where they collect in solid form. The system has been tested successfully with water from the Pacific, Atlantic and Indian Oceans. Valuable minerals – including lithium – can be extracted from the recovered solid salts: in experiments, 50% of the lithium in the salts was recovered. Growing water stress in the Mediterranean and the electric car industry's demand for lithium make the result, published by Tang et al. (2026) in Light: Science & Applications, particularly topical.
According to the UN, 2.2 billion people live without access to safe drinking water, and the situation is becoming more urgent as the climate changes. A research team at the University of Rochester has developed a solar desalination system with a black metal surface treated by femtosecond laser that turns seawater into drinking water without chemical pre-treatment or toxic brine. The metal surface absorbs almost all incoming sunlight while drawing in a thin layer of seawater through an extremely strong capillary effect. In the active zone, sunlight evaporates and distils the water, while salts and minerals migrate through microscopic grooves to the passive zone, where they are deposited in solid form.
One of the system's main innovations is the engineered use of the coffee-ring effect: the magnesium and calcium in seawater can form a hard crust that blocks the water's path – the carefully designed surface pattern prevents this. Tests with water from the Pacific, Atlantic and Indian Oceans confirmed that the system works continuously and self-regulates, with no brine waste.
The recovered solid salts are a potential raw material. In a related experiment using hydrogen titanate nanoparticles, the system recovered 50% of the lithium as a by-product of desalination – a strategically important development for the electric car industry and consumer electronics, since conventional lithium mining is extremely energy-intensive and environmentally burdensome.
Growing water stress in the Mediterranean, the EU's increasing need for desalination capacity and the energy transition's raw material shortages together make this result particularly topical. The study by Tang et al. (2026) in Light: Science & Applications was funded by the NSF, the Bill & Melinda Gates Foundation and the Worldwide Universities Network.
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