How much energy does it take to evaporate a liter of water? Quite a lot. It's the "thermal limit" that has always held back atmospheric water collection systems: excellent at absorbing humidity, terrible at releasing it. But what if, instead of heating the water to evaporate it, we shook it away with ultrasound? It's MIT's intuition: an actuator that vibrates at 20.000 cycles per second, extracting water droplets from the air in 2-7 minutes instead of the hours it takes in the sun.
The system achieves an energy efficiency of 428%, 45 times better than traditional thermal methods. Dry air hides water: you just need to vibrate it at the right frequency.
The starting problem: greedy materials that don't let go
Atmospheric water harvesting materials are ironically victims of their own success. They capture moisture with such tenacity that they then no longer want to release it.. The hydrogel, metal sponges, airgel: all very good at absorbing vapor from the air. Even in the driest deserts, there's always some atmospheric moisture to capture. The question is what happens next.
“Any material that is very good at capturing water doesn't want to separate from it,” he explains. Svetlana Boriskina, principal investigator in the Department of Mechanical Engineering at MIT. The study published in Nature Communications November 18, 2025 starts precisely from this paradox: Solar thermal systems can take hours, sometimes days, to recover the water captured by hygroscopic materials.
Too slow, too inefficient. And too dependent on the weather.
The solution: Make molecules dance and extract water from the air using ultrasound.
The turning point came from the meeting of two worlds. Ikra Iftekhar Shuvo, the study's lead author and a doctoral student in media arts and sciences, was working with ultrasound for wearable medical devices. Boriskina, meanwhile, was looking for a way to speed up the extraction of water from atmospheric materials. Boom, an explosive cocktail: the two research projects seemed made for each other.
Ultrasound is a sound pressure wave that vibrates above 20 kilohertz: invisible, inaudible, but physically powerful at the molecular level. The team designed an ultrasonic actuator composed of a flat ceramic ring that vibrates when it receives electrical voltage, surrounded by a second ring equipped with micronozzles. When the water-saturated hydrogel is placed on the device, the ultrasound breaks the weak hydrogen bonds that trap the water molecules.
“With the ultrasound we can precisely disrupt the weak bonds between water molecules and the sites where they are held,” Shuvo explains.
“It's as if the water is dancing with the waves, and this targeted disturbance creates a momentum that releases the water molecules.”
Finally, water droplets from the air fall through the nozzles into collection containers, above and below the vibrating ring.
The numbers: 45 times more efficient than the Sun
Tests in a climate chamber with varying humidity levels yielded clear results. The ultrasonic device released enough water to completely dry the absorbent material samples in 2-7 minutes. Conventional thermal systems require tens of minutes or hours to achieve the same result.
Energy efficiency speaks for itself: average consumption of 0,535 MJ/kg compared to 24 MJ/kg of thermal systems. 428% efficiency versus 9,5% solar evaporationThis is a 45-fold leap, exceeding the thermodynamic limit of the enthalpy of evaporation of water.
Practically, the system uses less energy than theoretically needed to evaporate the water, because it doesn't evaporate it at all: it shakes it off directly into the liquid state.
Multiple cycles: the real advantage
It's the extraction speed that changes everything. With solar thermal systems, you can run one cycle a day if all goes well; with ultrasound, you can run several. The hydrogel takes 40 minutes to absorb moisture from the air at 75% relative humidity. The piezoelectric actuator extracts it in 2 minutesAbsorption-extraction-absorption: continuous cycles powered by a small solar cell.
“It's about how much water you can extract per day,” Boriskina emphasizes.
"With ultrasound, we can recover water quickly and repeat the cycle over and over again. This can translate into considerable volumes over the course of a day."
Yes, but how much water can we get from the air, then?
Projections on a scaled system with 1 square meter of absorbing material suggest over 10 liters of water per day at 75% humidity. Even in the driest climates, where relative humidity drops to 30-40%, the system would maintain usable yields thanks to multiple cycles.
Water from the Air in 2 Minutes: From the Desert to Your Window (and Back Again)
“The beauty of this device is that it is completely complementary and can be added as a component to almost any absorbent material,” says Boriskina. The idea is a home application: A fast-absorbing material combined with a window-sized ultrasonic actuator. When the material reaches saturation, the actuator activates briefly using energy from a photovoltaic cell, releasing the collected water, and resetting for a new cycle.
The co-author Michael Garrett emphasizes how “by learning how our signals travel, we get valuable insights on how to design future systems.” The methods developed to model these weak signals could also be applied to astronomy, planetary defense, and environmental monitoring.
The work was supported by the MIT Abdul Latif Jameel Water and Food Systems Lab and the MIT-Israel Zuckerman STEM Fund. As I was already saying two years ago, atmospheric water harvesting is becoming a real market. Now with the ultrasound, it becomes even more so.
Air contains water. Always, even in deserts. And if we can make it "dance" fast enough, we'll have as much as we want.
