MIT Extracts Clean Water from Air 45x Faster with Ultrasound

Using ultrasound, MIT has created a powerful technique to extract and transform moisture in the air into clean water.

Recently published in Nature Communications, engineers at Massachusetts Institute of Technology (MIT) have developed a method to rapidly extract water from a material used for atmospheric water harvesting.

Instead of relying on the sun for water evaporation, the team uses ultrasonic waves to dislodge the water. 

Even in arid environments, a certain degree of humidity can be absorbed and extracted using appropriate materials, yielding clean drinking water. In recent years, researchers have created a variety of innovative sponge-like materials for this process, known as "atmospheric water harvesting."

However, extracting water from these materials typically requires both heat and time. Current designs depend on solar energy to evaporate water from the materials and subsequently condense it into droplets. This process, however, can span several hours or even days.

The researchers have created an ultrasonic apparatus that vibrates at a high frequency.

When a water-collecting material, referred to as a "sorbent," is positioned on the apparatus, it emits ultrasound waves specifically calibrated to dislodge water molecules from the sorbent.

The team discovered that the apparatus can recover water within minutes, in contrast to the tens of minutes or hours needed by thermal systems.

In contrast to heat-based designs, this device necessitates a power source. The team anticipates that a compact solar cell could provide the necessary power, while also functioning as a sensor to determine when the sorbent has reached its capacity.

Additionally, it could be programmed to activate automatically once a material has absorbed sufficient moisture for extraction. Consequently, this system could continuously absorb and release water from the air multiple times throughout a single day.

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. Now we have a way to recover water quickly and efficiently.

Svetlana Boriskina, Principal Research Scientist, Department of Mechanical Engineering, Massachusetts Institute of Technology (MIT)

Precious Hours

Boriskina’s team at MIT is engaged in the development of materials that interact with the environment in innovative ways.

The team investigated atmospheric water harvesting (AWH) and the design of materials that can effectively absorb moisture from the air. The objective is that, if these systems can operate reliably, AWH technology would greatly benefit communities where conventional sources of drinking water, and even saltwater, are limited.

Similar to other research groups, Boriskina’s laboratory had typically presumed that an AWH system deployed in the field would capture moisture at night, subsequently using solar heat during the day to evaporate the water and condense it for collection naturally.

Any material that’s very good at capturing water doesn’t want to part with that water. So you need to put a lot of energy and precious hours into pulling water out of the material.

Svetlana Boriskina, Principal Research Scientist, Department of Mechanical Engineering, Massachusetts Institute of Technology (MIT)

Boriskina came to understand that there might be a more efficient method for recovering water after Ikra Shuvo became a member of her team. Shuvo had experience using ultrasound in the context of wearable medical device applications.

As he and Boriskina brainstormed potential new projects, they recognized that ultrasound could serve as a means to accelerate the recovery phase in atmospheric water harvesting.

“It clicked: We have this big problem we’re trying to solve, and now Ikra seemed to have a tool that can be used to solve this problem,” recalled Boriskina.

Water Dance

Ultrasound, also known as ultrasonic waves, refers to acoustic pressure waves that propagate at frequencies exceeding 20 kilohertz (20,000 cycles per second). These high-frequency waves are neither visible nor audible to humans. Furthermore, the team discovered that ultrasound vibrates at an optimal frequency to dislodge water from a material.

With ultrasound, we can precisely break the weak bonds between water molecules and the sites where they’re sitting. 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.

Ikra Iftekhar Shuvo, Graduate Student, Massachusetts Institute of Technology (MIT)

Shuvo and Boriskina have developed a novel ultrasonic actuator aimed at extracting water from a material used in atmospheric water harvesting. Central to this device is a flat ceramic ring that vibrates upon the application of voltage.

This ring is encircled by an outer ring featuring numerous small nozzles. Water droplets that are dislodged from the material can fall through the nozzles into collection vessels positioned both above and below the vibrating ring.

The team conducted tests on a previously developed atmospheric water harvesting material. Utilizing quarter-sized samples of this material, they initially positioned each sample within a humidity chamber, which was adjusted to various humidity levels.

As time progressed, the samples absorbed moisture and reached saturation. Subsequently, the researchers placed each sample onto the ultrasonic actuator and activated it to vibrate at ultrasonic frequencies. In every instance, the device successfully expelled sufficient water to dry each sample within just a few minutes.

The researchers estimate that, in comparison to using solar energy, the ultrasonic design is 45 times more effective in extracting water from the same material.

“The beauty of this device is that it’s completely complementary and can be an add-on to almost any sorbent material,” said Boriskina, who envisions a practical, household system that might consist of a fast-absorbing material and an ultrasonic actuator, each about the size of a window.

Once the material reaches saturation, the actuator will momentarily activate, using energy from a solar cell, to expel the water. Subsequently, the material will be prepared to collect additional water, undergoing several cycles within a single day.

“It’s all about how much water you can extract per day. With ultrasound, we can recover water quickly and cycle again and again. That can add up to a lot per day,” added Boriskina.

MIT engineers design an ultrasonic system to “shake” water out of an atmospheric water harvester. The new design can recover captured water in minutes rather than hours. Video Credit: © Ikra Shuvo /MIT

Journal Reference:

Shuvo, I. I., et al. (2025) High-efficiency atmospheric water harvesting enabled by ultrasonic extraction. Nature Communications. DOI:10.1038/s41467-025-65586-2.