Synthetic trees could tap underground water in arid areas

They also could also help coastal residents mine fresh water from salty sources.

Synthetic trees could tap underground water in arid areas

If you put a narrow straw in a glass of water, some of that fluid will climb up the tube. But without help, that water will climb only a small distance. Now, researchers have come up with a device that can mimic trees’ ability to make water climb great heights. That could bring drinking water to communities that don’t now have enough.

Described as a “synthetic tree,” this new device could help people more easily tap into groundwater, scientists say. It might also let people in coastal areas mine fresh drinking water from the sea.

Water molecules find each other really attractive. That’s why large numbers of them come together to form round droplets. Sometimes, however, water molecules are more attracted to other substances than to themselves. That’s why they climb up the sides of a glass. (Did you ever notice that the surface of the water in a glass curves upward where it meets the side of the glass?) In a very narrow tube, water can even climb a few centimeters (a couple of inches or so), notes Jonathan Boreyko. He’s a materials scientist at Virginia Tech in Blacksburg. The process driving this climb is called capillary action. But for water to rise more than a few centimeters, that capillary action needs help.

Plants know the secret to helping, Boreyko explains. Throughout the day, water evaporates out a plant’s leaves. This creates suction inside a tissue called xylem (ZY-lem). That suction pulls water and nutrients up through the roots to nourish leaves and new growth. Such suction can lift water to the tree tops. Now, Boreyko and his teammates have designed a “synthetic tree.” They say it can help people living in dry areas harvest water from even deep underground.

The guts of the ‘tree’

Ndidi Eyegheleme is a mechanical engineer. She grew up in a small coastal village in Africa. Today she works with Boreyko at Virginia Tech. “Where we lived was surrounded by salty water,” she recalls. “So, we had a lot of challenges getting fresh water to drink.” That’s why she’s so interested in making synthetic trees. They could help people in dry parts of the world, too, she adds. Worldwide, about 2.2 billion people lack reliable access to clean drinking water, the United Nations reports. Yet in some places, water may be just a few meters (yards) below their feet.

The Virginia Tech team recently built a prototype synthetic tree inside a clear plastic box. It’s small enough to sit on a benchtop. Nineteen small plastic tubes serve as this tree’s “trunk.” The inside diameter of each tube is about six times the diameter of the lead in a pencil. Each tube carries water up from a container to a ceramic “leaf” that’s a tad larger in diameter than a soda can. Just like a real leaf, this ceramic disk has many tiny pores. Evaporation from those pores creates the suction that helps pull water up the tubes.

This leaf from a synthetic tree (at left in box, and closeup in inset) could help slurp up water through long tubes in the soil. That could let people tap drinking water from dozens of meters (yards) underground, a new study suggests. Eyegheleme et al/Applied Physics Letters 2021

The team also sprayed a coating of graphite (the material that makes up pencil lead) onto their synthetic leaf. This darkened the leaf’s surface to boost how much it heats up in sunlight or under a bright lamp. That boosted evaporation — and water suction — even more. Finally, the team added a cooling pad to chill the part of the box that holds the tree. Water vapor condenses there to create pure water.

The team described its system June 22 in Applied Physics Letters.

Imitating nature

Mimicking how a tree slurps water “is a wonderful approach,” says Xianming Dai. He’s a mechanical engineer at the University of Texas at Dallas. Synthetic trees might be able to tap water as much as 100 meters (328 feet) underground, he says. He advises bundling the tree trunk’s long fragile tubes inside a larger protective pipe. That way the team’s system should be easy to scale up to larger sizes.

Such devices also could be modified to help people generate fresh water from salty, says Dai. How? Install a membrane that removes dissolved salt from water before it enters the lower end of the tubes. That would help prevent salt crystals from forming in the tubes or clogging the leaf as water evaporates, he notes.

Key to making this tree energy-efficient was heating and evaporating only the water inside the synthetic leaf, not the entire pool of water below it, says Hadi Ghasemi. He’s a mechanical engineer at the University of Houston in Texas. “If you only have to heat a small amount of water, you have a much-reduced need for energy,” he notes.

Each square meter (about 10.8 square feet) of “leaf” could generate about 1.6 liters (0.42 gallon) of water per hour, the Virginia Tech researchers say.

This is one in a series presenting news on technology and innovation, made possible with generous support from the Lemelson Foundation.

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Cloning boosts endangered black-footed ferrets

A cloned ferret named Elizabeth Ann brings genetic diversity to a species that nearly went extinct in the 1980s.

Cloning boosts endangered black-footed ferrets

On December 10, 2020, a new baby black-footed ferret came into the world. Her species is one of the most endangered in North America. Named Elizabeth Ann, she quickly grew up into a chattering, tumbling, nipping ball of energy. This little girl doesn’t know it, but she could be key to saving her species.

Kimberly Fraser is an education specialist at the National Black-footed Ferret Conservation Center in Wellington, Colo. And she knows Elizabeth Ann well. “She loves getting in tubes and boxes and paper bags. I would say she’s very happy,” Fraser says.

Elizabeth Ann is a clone who brings much-needed genetic diversity to her endangered species. In the coming years, her handlers hope that she will have babies of her own and will spread her special genes through the black-footed ferret population. USFWS National Black-footed Ferret Conservation Center

What makes this little ferret special is that she is a clone. She’s a genetic copy of an animal that died decades ago.

More than five million black-footed ferrets once lived on the great plains of North America. They were cunning hunters that preyed almost entirely on prairie dogs. When European settlers moved to the area and built farms, they destroyed these animals’ habitats. They also poisoned and killed prairie dogs, leaving many black-footed ferrets without food. A plague also spread through the populations of both species. In 1979, experts declared the black-footed ferret extinct.

But then, in 1981, there was “an electrifying announcement,” recalls Oliver Ryder. A farmer in Wyoming had discovered a small community of wild black-footed ferrets! Ryder, now a genetics expert at San Diego Zoo Wildlife Alliance in California, was elated. Conservationists captured the wild ferrets and began a captive-breeding program. They hoped to save the species.

Ryder had the foresight to ask for cell samples from several of the animals that were captured. “It will be useful for reasons we don’t know,” he recalls saying. For each animal, he received a little glass vial containing a tiny piece of skin. The cells from this skin were preserved in a way that makes it possible to revive and grow them.

Back then, he couldn’t have imagined how very useful these preserved cells would turn out to be.

Rebuilding a population

The captive-breeding program was challenging. The plague still threatened prairie dogs and ferrets. Over time, though, scientists have been able to reintroduce wild ferrets to parts of Wyoming, Montana, South Dakota, Arizona, Mexico and elsewhere. Scientists also developed a vaccine for the plague. The wild population now numbers around 350, with around 300 more still living in captivity.

A cloned ferret named Elizabeth Ann is bringing genetic diversity to a species that nearly went extinct.

However, only seven of that original captured ferret population had pups that survived to have babies of their own. That meant every black-footed ferret in the world was closely related. They all had very similar genes. With each generation, offspring were more likely to have genetic problems. They needed genetic diversity to survive, says Samantha Wisely. She is a genetics expert who studies conservation at the University of Florida in Gainesville.

Enter Elizabeth Ann. She is a clone of Willa, one of the ferrets whose cells Ryder preserved back in 1986. Until 2020, Willa had no living descendants. So her genes were quite different from the rest of the species. Elizabeth Ann’s birth was “a leap of hope” for the species, says Fraser. Wisely was also excited. “I was over the moon,” she says.

a diagram shows the process for cloning Elizabeth Ann the black-footed ferret
Elizabeth Ann’s genetic information was copied from one black-footed ferret. Here is how the cloning process worked. A domestic ferret acted as a surrogate mother for Elizabeth Ann.Journal of Heredity

In the cloning process, scientists removed the entire nucleus, or middle, from Willa’s cells. This nucleus contains genes that are akin to a recipe for creating an animal identical to Willa. Researchers also took egg cells from a domestic ferret and removed their nuclei. Then they transferred Willa’s nuclei into these egg cells. The egg cells began to divide, becoming embryos. The researchers then put the embryos into another domestic ferret. This ferret carried the babies until they were born.

The only embryo to survive the entire process was Elizabeth Ann. Her birth showed that it is possible for DNA from a creature that died many years earlier to live again — and potentially boost an entire species.

Meanwhile, Ryder continues to collect cells from as many animal species as possible. He thinks this work is important because, “We love the world we live in and we want to protect it.”

The collection he works on is called the Frozen Zoo. It has samples from more than 1,100 different animal species so far. Almost all are mammals, birds, reptiles and amphibians. But at least 13,000 of these types of animals are threatened or endangered with extinction. He hopes that researchers will donate cells from as many of these species as possible. And then maybe someday, someone will use those cells to save another species.

Genetics researcher Oliver Ryder holds up a test tube sample of animal cells
Genetics researcher Oliver Ryder holds a sample of animal cells that were donated to the Frozen Zoo in San Diego, Calif. Cells like these can allow genetic engineers to rescue an endangered species. Someday, they may even resurrect extinct ones. San Diego Zoo Wildlife Alliance
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