People can sleep in the most basic quarters and scrape together a meal from the most modest of ingredients. But without clean water we can not survive. And in places where water is scarce-in the deserts of the world, for example-water to people requires technical skills and irrigation that can be cumbersome and expensive.
Two new studies by researchers at Ohio State University offer a possible solution inspired by nature.
"We thought," How can we collect water from the surrounding air around us? Said Bharat Bhushan, Ohio Eminent Scholar and Howard D. Winbigler, Professor of Mechanical Engineering, Ohio State, "and so we have dealt with the things of nature that are already doing: the cactus, the beetle, desert grasses." [1
Bhushan's work focuses on finding nature-inspired solutions to societal issues, in which case his research team in the desert looked for a life that could survive despite limited access to water.
All cacti, beetles, and Desert grasses collect condensed water from the night mist, collect droplets from the air, and filter them to the roots or reservoirs that provide enough water to overflow
Drops of water collect on wax-free, water-repellent bumps on the back of a beetle and then glide on the flat surface between the bumps towards the beetle's mouth. Desert grasses collect water at their tips and then channel it through channels in each blade to their root systems. A cactus collects water from its barbed spikes before moving the conical spines down to the base of the plant.
Bhushan's team studied each of these creatures and realized that they could build a similar – albeit larger – system so that people could draw water from nocturnal fog or condensation.
They began to investigate how different surfaces could collect water and which surfaces could be the most efficient. Using 3D printers, they built surfaces with bumps and barbs and created misty environments with a commercial humidifier to see which system was collecting the most water.
They learned that conical shapes absorb more water than cylindrical shapes – "which made sense given the knowledge of the cactus," Bhushan said. The reason for this is the physical phenomenon Laplace pressure gradient. Water collects at the top of the cone and then flows down the slope of the cone, where a reservoir waits.
Grooved surfaces move water faster than un-grooved areas – "which in hindsight is obviously grass, because of our knowledge," Bhushan said. In the experiments of the research team, grooved surfaces collected about twice as much water as un-grooved surfaces.
The materials that make up the cones were also made of matter. Hydrophilic surfaces – those that allowed the water to be pried open instead of absorbing it – collected most of the water.
"Beetle surface material is heterogeneous, with hydrophilic spots surrounded by hydrophobic areas, making it easier for water to flow to the beetle's mouth, Bhushan explained.
The research team also experimented with a structure containing several cones and learned that more water could accumulate when water droplets could merge between cones one or two millimeters apart, and the team continues these experiments, Bhushan said.
So far, only laboratory-level work has been done, but Bhushan sees expanding the work with structures in the desert that could collect water from fog or condensed water that could supplement water from public systems or wells, either door to door or community wide.
There is a precedent for the idea: In Areas around the world, including In the Atacama Desert in Chile take gr Onet nets water from the mist and collect it in reservoirs that farmers and others can use. Bhushan believes that these nets might not be the most efficient way to use water from the air.
"Water supply is a very important issue, especially for people in the driest parts of the world," Bhushan said. "By using technology with biological inspiration, we can help meet the challenge of providing people around the world with clean water as efficiently as possible."
Inspired by a desert beetle, cactus and pitcher plant, researchers are designing a new material for collecting water droplets
Dev Gurera et al., Design of Bioinspired Surfaces for Water Collection from Nebula, Philosophical Transactions of the Royal Society A: Mathematical, Physical, and Technical Sciences (2018). DOI: 10.1098 / rsta.2018.0269