Researchers at the Massachusetts Institute of Technology (MIT) made a discovery that could lead to more efficient power plants and new way of extracting energy from the atmosphere, according to a press release.

The researchers were performing work on an extension of a previous project when they unexpectedly discovered tiny water droplets to cause an electrical charge when they form on a super-hydrophobic surface and "jump" off.

The previous work, from the same team, showed the droplets could in fact leap off the super-hydrophobic surface instead of simply rolling down and dropping due to gravity. The spontaneous leaping occurs when the droplets of water condense on a metal surface with a certain super-hydrophobic coating and with the release of excess surface energy.

"We found that when these droplets jump, through analysis of high-speed video, we saw that they repel one another midflight," co-author Nenad Miljkovic, an MIT post-doctoral student, said. "Previous studies have shown no such effect. When we first saw that, we were intrigued."

The researchers were able to confirm the reaction of the water droplets was caused by a net positive electrical charge by introducing an electrode. When they used a positively charged electrode, the droplets were repelled, but the negatively charged one attracted them toward it.

During the charging process, the droplets form a double layer of paired positive and negatively charged surfaces. The leaping occurs when neighboring droplets coalesce and the two different charges separate extremely quickly.

The authors reported their findings in the journal Nature Communications.



Miljkovic said the whole process is so fast, "It leaves a bit of charge on the droplet, and the rest on the surface."

Because the droplets could jump off of a condenser surface, a component vital to most of the world's electricity-generating power plants, many could benefit from the researcher's findings. With the proper mechanism, power plants all over the world could become more energy efficient.

Miljkovic also said there is another use for the team's discovery: converting ambient air condensation into power. He said this would be made possible by placing two metal plates parallel to one another with droplets jumping off one and being collected by the other.

"You just need a cold surface in a moist environment," Miljkovic said. "We're working on demonstrating this concept."