The United Nations estimates that 2.2 billion people lack safely managed drinking water, and communities from California to the Middle East rely on desalination plants to convert ocean water to fresh water. Common desalination techniques such as reverse osmosis and thermal distillation are energy-intensive, require pre- and post-water treatment, and leave behind a concentrated saltwater byproduct called brine that wreaks havoc on sea life when it’s deposited back into the ocean by raising the salt level and lowering oxygen in the water.
But a novel approach developed at the University of Rochester offers a way to overcome these drawbacks. Researchers at URochester’s Institute of Optics developed a new solar-thermal desalination process to produce fresh water in an energy-efficient way that does not leave behind brine and requires no chemical additives to pre-treat the water. A team led by Chunlei Guo, Professor of Optics and Physics, Senior Scientist, URochester’s Laboratory for Laser Energetics, described their method in a paper published in Light: Science & Applications.
The technology uses solar panels made of black metal etched with femtosecond lasers to make the surface super light absorbing and superwicking — or extremely attractive to water. The panels have a laser-treated active region that pulls a thin layer of water across the surface, absorbs nearly all solar radiation, distills the water, and deposits the leftover salts and minerals into the panel’s untreated sides or “passive” region so that the salt does not clog the active region and disrupt continuous desalination.
Guo says other researchers have developed solar-thermal desalination techniques that work well in lab experiments using simulated seawater made of only water and sodium chloride. As the water evaporates, the sodium chloride crystalizes in a grainy and porous fashion allowing water to pass through to dissolve the salt and the solar panels can be easily cleaned.
But real ocean has a much more complex composition, and these systems tend to encounter issues when tested in the field. Unlike sodium chloride, many other components in seawater such as magnesium- and calcium-based materials crystallize in a crusty and non-porous fashion on the solar panel’s surface, clog it, and eventually water can no longer seep through. This is the same phenomenon as your shower head clogging up over time or your tea pot lined with scales, except that seawater contains hundreds of times more salts than your tap water.
To keep their solar panel surface from gumming up in a similar way, Guo’s team precisely etched the black metal’s grooves so the various salts and minerals in ocean water would simply slough off. They also leveraged a physical phenomenon that has plagued clumsy javaphiles for centuries: the coffee ring effect.
“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,” said Guo. “We use that same principle to advance the salts to the passive region.”
Testing their solar-thermal desalination technique using samples of water from the Pacific, Atlantic, and Indian Oceans, Guo and his team were able to make the surface self-cleaning so that it extracted freshwater and directed the remaining salts to the passive region where they could be later collected without reducing the panel’s efficiency.
One of the new method’s distinct advantages is that instead of leaving behind brine that must be disposed of or processed, it extracts nearly 100 percent of the salts in solid form. This could not only produce an abundant supply of table salt, but it could also be used to extract more precious minerals, including lithium, which is used in the lithium-ion batteries that power electric vehicles and other electronics.
In a related paper in the Journal of Materials Chemistry A, Guo and his colleagues showed how they can use the same superwicking solar panels to separate lithium from the rest of other salts in desalination. Embedding nanoparticles made of hydrogen titanate in the tiny grooves of the black metal surface isolates the lithium from other salts and minerals.
“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,” said Guo.
Using water samples from Great Salt Lake, the researchers were able to extract about 50 percent of the lithium from the salts left behind by the desalination process.
Guo said now that the superwicking desalination technology has been demonstrated in proofs of concept on small-scale devices, he sees the technology inherently scalable, capable of improving global access to drinking water and building more sustainable supply chains for precious minerals.
Here is an exclusive Tech Briefs interview, edited for length and clarity, with Guo.
Tech Briefs: What was the biggest technical challenge you faced while developing this solar-thermal desalination process?
Guo: The biggest technical challenge was making the system work with real seawater, not just simple simulated saltwater made in the lab. Real seawater contains many minerals, such as magnesium and calcium, that can form hard scale and clog a desalination system. Our key advance was introducing our black superwicking surface to solar desalination. This wicking, self-cleaning surface moves salts away from the evaporation area, allowing the system to continue operating at high efficiency.
Tech Briefs: Can you please explain in simple terms how it works?
Guo: We use a black superwicking surface invented in my lab using ultrafast laser processing. The surface absorbs sunlight very efficiently and also pulls a thin layer of water uphill across itself. Sunlight evaporates the water, which is then collected as fresh water. Meanwhile, the salts are moved away from the black wicking area and collected separately as solids rather than discharged as waste brine. This approach also allows us to recover valuable minerals, such as lithium.
Tech Briefs: Do you have any updates you can share?
Guo: For this technology, the underlying materials and fabrication methods are scalable, and we are actively exploring that path while also welcoming industrial partnerships.
Tech Briefs: Do you have any set plans for further research/work/etc.? If not, what are your next steps?
Guo: We are working on scaling up the technology. At the same time, we are also expanding the platform by integrating the desalination technology with other mature systems, such as photovoltaic solar cells. In that direction, we have demonstrated that the desalination process can be used to cool the solar cells, improving electrical output while simultaneously producing freshwater. This creates a synergistic water-energy system in which sunlight generates both electricity and clean water at the same time. Here are some of our recent efforts in that direction.
https://doi.org/10.1016/j.xcrp.2025.102734
https://doi.org/10.1002/adsu.202500857
Tech Briefs: Do you have any advice for researchers aiming to bring their ideas to fruition?
Guo: I would be hesitant to tell other researchers how to conduct research. Science advances because people bring diverse perspectives and approaches to solving problems. One lesson from our own work is that many technologies perform well under ideal laboratory conditions but encounter challenges when exposed to real operating environments. In our case, we deliberately moved beyond simulated seawater widely used in the research community and developed our technology with real ocean water. That experience revealed important challenges and ultimately led to a more practical and robust solution.
Tech Briefs: Is there anything else you’d like to add that I didn’t touch upon?
Guo: We see our technology as more than a desalination method; it is a possible platform for clean water production, renewable energy support, and sustainable resource recovery.
