Complex patterns of motion emerge when water drops condense on an oiled surface.

A more efficient way to capture fresh water from the air could be inspired by a phenomenon of motion first glimpsed in bowls of breakfast cereal.

KAUST researchers have observed that, when water droplets condense from the air onto a cold surface coated with oil, the droplets commence a complex dance. This motion — akin to a process known as the Cheerios effect whereby the floating cereal tends to cluster due to surface tension — could help to speed up the harvesting of water from the atmosphere in arid regions such as Saudi Arabia.

“We are interested in designing surfaces that can promote condensation of water, which has important heat-transfer and water-harvesting applications,” says Marcus Lin, a research fellow in the lab of Dan Daniel, who led the research. On a typical solid surface, condensed droplets stick to the surface with minimal motion. “Think of water condensing on a cold soda can,” says Lin. “The droplets only move once they grow big enough for gravity to pull them down.”

Daniel, Lin and their collaborators had the idea that adding a thin film of oil would lubricate the surface, resulting in highly mobile droplets that would free up space for further droplet condensation, boosting condensation rates. The idea worked — but the complex ways in which the droplets moved was a complete surprise, Daniel says.

Read more at KAUST Discovery.