Ikra Iftekhar
MIT researchers discovered how to use sound wave vibrations to release water molecules from a storage medium, greatly accelerating the extraction of drinking water from air.
Scientists worldwide are exploring a variety of materials—from specialized paints to spongy aerogels and substances with extremely high surface areas—to extract water from the air.
Even in arid regions, the atmosphere contains water, and tapping into it could supply clean drinking water to millions without access to freshwater or municipal systems.
The Energy Challenge in Releasing Captured Water
A major challenge with many existing methods is that once a material captures water from the air, people must apply heat to release and condense it into usable drinking water.
“Any material that excels at capturing water holds on tightly to it,” explains MIT’s Svetlana Boriskina. “Extracting that water requires a lot of energy and valuable time.”
Earlier this year, MIT researchers developed a passive water harvester that uses a bubble-wrap-like material and solar heat to evaporate the captured water, avoiding an external energy source. However, the process can be slow in producing clean drinking water.
Releasing Water with Sound Waves
Now, Boriskina, a principal research scientist in MIT’s Department of Mechanical Engineering, and her team have devised a new—and much faster—method to release water harvested from air: using sound waves.
The team built a flat-plate ultrasonic actuator with a water-saturated harvesting material at its center.. When the researchers activated the actuator, it directed ultrasonic waves—frequencies above 20 kilohertz—at the material.
The ultrasonic waves caused the material to release all its water as droplets within just two to seven minutes. The plate’s design guided the droplets through nozzles into a collection area. A visualization illustrates the process in action.
“Ultrasound breaks the weak bonds holding water molecules,” explains Ikra Iftekhar Shuvo. “The vibrations give them momentum, releasing them as droplets.”
The researchers report that the device can extract water at a rate 45 times faster than solar heating. While the ultrasonic actuator does require a small amount of electricity, it could be powered by an attached solar cell.
Versatile and Solar-Powered Water Harvesting
“The advantage of this device is its versatility—it can be paired with nearly any water-absorbing material,” says Boriskina. Once saturated, the actuator uses solar power to release water, readying the material for repeated daily cycles.
Boriskina envisions a home system using fast-absorbing material and a window-sized actuator to pull drinking water from the air.
“It ultimately comes down to how much water you can harvest each day,” she says. “Ultrasound lets us release water quickly and repeat the process multiple times, which can result in a substantial daily yield.”
Read the original article on: New Atlas
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