In places where water is scarce — the world's deserts, for example — obtaining clean water requires feats of engineering and irrigation that can be cumbersome and expensive, but 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?' So, we looked to the things in nature that already do that: the cactus, the beetle, desert grasses," said Bharat Bhushan, Ohio eminent scholar and the Howard D. Winbigler professor of mechanical engineering at Ohio State.

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

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 to provide enough hydration to survive, Ohio State said.

Drops of water collect on wax-free, water-repellant bumps on a beetle's back and then slide toward the beetle's mouth on the flat surface between the bumps. Desert grasses collect water at their tips and 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 that they could build a similar, but larger, system to allow people to pull water from nighttime fog or condensation.

They started studying the ways different surfaces might collect water and which surfaces might be the most efficient. Using 3D printers, they built surfaces with bumps and barbs and 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 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 and 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. Hydrophilic surfaces — those that allow water to bead up rather than absorbing it — gathered the most water.

"The beetle's surface 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 1-2 mm 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. He believes that water could supplement water from public systems or wells.

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; however, those nets might not be the most efficient way of harnessing water from the air, Bhushan said.

"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 clean water to people around the globe in as efficient a way as possible."