Collecting clean water from air, inspired by desert life

cactus
Credit: CC0 Public Domain

Humans can get by in the most basic of shelters, can scratch together a meal from the most humble of ingredients. But we can't survive without clean water. And in places where water is scarce—the world's deserts, for example—getting water to people requires feats of engineering and irrigation that can be cumbersome and expensive.

A pair of new studies from researchers at The Ohio State University offers a possible solution, inspired by nature.

"We thought: 'How can we gather water from the ambient air around us?'" said Bharat Bhushan, Ohio Eminent Scholar and Howard D. Winbigler Professor of mechanical engineering at Ohio State. "And so, we looked to the things in nature that already do that: the cactus, the beetle, desert grasses."

Their findings were published Dec. 24 in the journal Philosophical Transactions of the Royal Society. The works were co-authored with Ohio State Ph.D. student Dev Gurera and with Ohio State engineering researcher Dong Song.

Bhushan's work focuses on finding nature-inspired solutions to societal problems. In this case, his research team looked to the desert to find life that survives despite limited access to water.

The cactus, beetle and desert grasses all collect water condensed from nighttime fog, gathering droplets from the air and filtering them to roots or reservoirs, providing enough hydration to survive.

Drops of water collect on wax-free, water-repellant bumps on a beetle's back, then slide toward the beetle's mouth on the between the bumps. Desert grasses collect water at their tips, then channel the water toward their root systems via channels in each blade. A cactus collects water on its barbed tips before guiding droplets down conical spines to the base of the plant.

Bhushan's team studied each of these living things and realized they could build a similar—albeit larger—system to allow humans to pull water from nighttime fog or condensation.

They started studying the ways by which different surfaces might collect water, and which surfaces might be the most efficient. Using 3-D printers, they built surfaces with bumps and barbs, then created enclosed, foggy environments using a commercial humidifier to see which system gathered the most water.

They learned that conical shapes gather more water than do cylindrical shapes—"which made sense, given what we know about the cactus," Bhushan said. The reason that happens, he said, is because of a physics phenomenon called the Laplace pressure gradient. Water gathers at the tip of the cone, then flows down the cone's slope to the bottom, where a reservoir is waiting.

Grooved surfaces moved water more quickly than ungrooved surfaces—"which seems obvious in retrospect, because of what we know about grass," Bhushan said. In the research team's experiments, grooved surfaces gathered about twice as much water as ungrooved surfaces.

The materials the cones were made out of mattered, too. Hydrophobic surfaces—those that allowed water to bead up rather than absorbing it—gathered the most water.

"The beetle's material is heterogeneous, with hydrophilic spots surrounded by hydrophobic regions, which allows water to flow more easily to the beetle's mouth," Bhushan explained.

The research team also experimented on a structure that included multiple cones, and learned that more water accumulated when water droplets could coalesce between cones that were one or two millimeters apart. The team is continuing those experiments, Bhushan said.

The work so far has been done on a laboratory-only level, but Bhushan envisions the work scaled up, with structures in the desert that could gather water from fog or condensation. That water, he thinks, could supplement water from public systems or wells, either on a house-by-house basis, or on a community-wide basis.

There is precedent for the idea: In areas around the world, including the Atacama Desert in Chile, large nets capture water from fog and collect it in reservoirs for farmers and others to use. Those nets might not be the most efficient way of harnessing from the air, Bhushan believes.

"Water supply is a critically important issue, especially for people of the most arid parts of the world," Bhushan said. "By using bio-inspired technologies, we can help address the challenge of providing to people around the globe, in as efficient a way as possible."


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Inspired by a desert beetle, cactus and pitcher plant, researchers design a new material to collect water droplets

More information: Dev Gurera et al, Designing bioinspired surfaces for water collection from fog, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences (2018). DOI: 10.1098/rsta.2018.0269
Citation: Collecting clean water from air, inspired by desert life (2018, December 26) retrieved 25 June 2019 from https://phys.org/news/2018-12-air-life.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Dec 26, 2018
We can always carry water bottles with us or avoid deserts. So, Rather focus more on Renewable Energy. It may be critical in some other countries, yes. Use Bulls to pull discharged batteries in thermal springs from 1 side to the other for charging them. Bulls can be eaten, when they get old. Using Vehicles to pull is wasting Fossil fuel. Use Bulls on both sides of the spring for similar purpose.
https://news.stan...114.html

Dec 26, 2018
We can always carry water bottles with us or avoid deserts. So, Rather focus more on Renewable Energy. It may be critical in some other countries, yes. Use Bulls to pull discharged batteries in thermal springs from 1 side to the other for charging them. Bulls can be eaten, when they get old. Using Vehicles to pull is wasting Fossil fuel. Use Bulls on both sides of the spring for similar purpose.
https://news.stan...114.html

https://www.nbcne...na836416

Dec 26, 2018
I like the idea of imitating natural plant processes that store/use the runoff water from nighttime fog. Following in the footsteps of Nature is a hardier way than having to lug several liters of water "over the river and through the woods" and then wondering how to get fresh drinking water once the liter bottles are empty.
Hopefully, the engineering folks will be able to closely imitate the plants to invent some nice new cones/bottles, etc. for human use wherever water is scarce.

Dec 27, 2018
We can always carry water bottles with us or avoid deserts. So, Rather focus more on Renewable Energy. It may be critical in some other countries, yes. Use Bulls to pull discharged batteries in thermal springs from 1 side to the other for charging them. Bulls can be eaten, when they get old. Using Vehicles to pull is wasting Fossil fuel. Use Bulls on both sides of the spring for similar purpose.
https://news.stan...114.html
https://en.wikipe..._battery

Dec 27, 2018
We can always carry water bottles with us or avoid deserts. So, Rather focus more on Renewable Energy. It may be critical in some other countries, yes. Use Bulls to pull discharged batteries in thermal springs from 1 side to the other for charging them. Bulls can be eaten, when they get old. Using Vehicles to pull is wasting Fossil fuel. Use Bulls on both sides of the spring for similar purpose.
https://news.stan...114.html
https://www.youtu...wyGv0nFM

Dec 28, 2018
All these ideas have been published recently in numerous publications. It seems it was published in a philosophical journal but even philosophers should know that nothing not even plants can violate the conservation of energy. How much water vapor is held is a liter of air in the Atacama Desert on an average day and how much energy does it take to convert a liter of water vapor to a liter of liquid water? I am tired of explaining. The article is an embarrassment.

Dec 28, 2018
All these ideas have been published recently in numerous publications. It seems it was published in a philosophical journal but even philosophers should know that nothing not even plants can violate the conservation of energy. How much water vapor is held is a liter of air in the Atacama Desert on an average day and how much energy does it take to convert a liter of water vapor to a liter of liquid water? I am tired of explaining. The article is an embarrassment.


Oh dear... Let's just consider two things:-
1. "The Philosophical Transactions of the Royal Society (Phil. Trans.) is a scientific journal published by the Royal Society of London. It was established in 1665, making it the first journal in the world exclusively devoted to science, and it has remained in continuous publication ever since, making it the world's longest-running scientific journal. "

2. No energy is "required" to convert water vapour to liquid water. Energy is released.

Dec 28, 2018
"Philosophical Transactions" is one of the oldest and most respected scientific journals in the history of science. Newton, Leeuwenhoek, Franklin, Darwin, Maxwell, Faraday, Turing, and Hawking have all been published in its pages. It's not "philosopy." Back in the day, what we now call "science" was called "natural philosophy."

Dec 28, 2018
flimflam's comment is an ideological tirade for altright political correctness.

If the publishing journal had been titled " Little Red Book pf Chairman Putin"?

flimflam would have swallowed the research findings.
Whole, without a second thought.

This is the reactionary assault on the Sciences & Arts.
For centuries artists were scientists, Scientists were artists.

It has been in this last century, with the corrupting influence of the pseudo-conservative, fakir-libertarian, racist evangelical. That there has been a malignant separation forced between the arts & sciences.

For those crawling through the muck of fake masculinity? The Arts seem an easy target. One they can safely attack without consequence. & now, they can safely attack the Sciences.

The Sciences are "how", we as a Society accomplish deeds. The Arts are "why" we as Humanity make the effort.

The altright-fairytails embracing irrelevancy, are the obsolete remnants of historical failures.

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