MIT Engineers Develop Ultrasonic Device That Shakes Water Loose from the Sky

Photo credit: Ikra Iftekhar
Engineers at MIT created a flat device that hums with sound waves too rapid for human ears to detect. These waves rattle water droplets from materials absorbed from the air, converting humidity into a constant stream of clean liquid. In areas where taps run empty and rivers remain far, this system offers a quiet revolution. There are no large factories or endless pipes necessary. Just air, a little vibration, and a few ingenious bits operating in tandem.

Svetlana Boriskina, a researcher in mechanical engineering at the school, leads the effort. She points out how air everywhere holds traces of water, even in the harshest deserts. “People have been looking for ways to harvest water from the atmosphere, which could be a big source of water particularly for desert regions and places where there is not even saltwater to desalinate,” she says. Her team combined this novel extractor with sorbents, which are sponge-like compounds that absorb moisture from the air. Older designs are adequate in trapping water, but the process of getting it out takes awhile. Heat from the sun works in theory, but it requires hours, if not days, of waiting. Boriskina’s gang desired speed without the delay.

In the center is a ceramic ring, no larger than a coaster in their early models. When you apply a jolt of electricity, it begins to quiver at almost 20,000 cycles per second. Place a damp sorbent directly on top, and the shaking will target the areas where water clings tightly. Ikra Iftekhar Shuvo, the graduate student who wrote the paper on this, explains it himself. “With ultrasound, we can break the weak bonds between water molecules and the sites where they’re sitting,” he says. “It’s like the water is dancing with the waves, and this targeted disturbance creates momentum that releases the water molecules, and we can see them shake out in droplets.” Tiny nozzles around the edges catch the drops as they fly free and direct them into a cup or basin. A small solar panel powers the whole thing, and turns on when the sorbent is full.


Tests were run in sealed chambers simulating muggy nights and bone-dry dawns. Quarter-sized chunks of sorbent were soaked overnight and then vibrated. Every last drop came out in two to seven minutes. Compare that to sun-kissed competitors and the numbers add up fast: 45 times the pull in a fraction of the time. No burning or long bake in the sun required. The sorbent dries quickly and is ready for another pull from the air. Run it four or five times a day and the yield increases fast. Boriskina nailed the math. “It’s all about how much water you can extract per day,” she says. “With ultrasound, we can extract water quickly and cycle again and again. That can add up to a lot per day.”


When scaled down to a household rig, the setup fits on a windowsill. A pane-sized sheet of sorbent absorbs moisture while you sleep. In the morning, the ring below buzzes for a few minutes and spits out enough for coffee or a rinse. Increase the size of the panels and households in hot climates could fill jugs by lunchtime. Shuvo’s background in medical devices helped him fine-tune the waves, drawing on technology that explores bodies without cutting. Co-authors Carlos Díaz-Marín and others from the mechanical engineering crew built the thing and tested it in the lab with precision equipment. Their paper is in Nature Communications and the blueprints are available for anyone with a workshop.
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