New Study Unveils Sunlight's Electric Field Role in Water Evaporation

A recent study conducted by researchers at North Carolina State University has uncovered the critical role played by the oscillating electric field of sunlight in enhancing the evaporation of water. The research, published in the journal *Materials Horizons* on June 24, 2025, reveals that solar radiation is more effective in evaporating water than conventional heating methods, a phenomenon previously not fully understood.

According to Saqlain Raza, a Ph.D. student and the first author of the paper, "It's well established that the sun is exceptionally good at causing water to evaporate—more efficient than heating water on the stove, for instance. However, it has not been clear exactly why. Our work highlights the role that electric fields play in this process."

The study, titled *Oscillations in Incident Electric Field Enhances Interfacial Water Evaporation*, explores the mechanisms behind this phenomenon through computational simulations. The researchers manipulated various parameters of sunlight to observe their effects on water evaporation. Jun Liu, co-corresponding author of the paper and an associate professor of mechanical and aerospace engineering at NC State, explained, "Light is an electromagnetic wave, which consists—in part—of an oscillating electric field. We found that if we removed the oscillating electric field from the equation, it takes longer for sunlight to evaporate water. But when the field is present, water evaporates very quickly. The stronger the electric field, the faster the water evaporates. The presence of this electric field is what separates light from heat when it comes to evaporating water."

The researchers identified two main processes occurring during evaporation: the release of individual water molecules and the release of water clusters—finite groups of interconnected water molecules. Raza noted, "We found that the oscillating electric field is particularly good at breaking off water clusters. This is more efficient, because it doesn't take more energy to break off a water cluster (with many molecules) than it does to break off a single molecule."

The study further demonstrated this concept through simulations comparing pure water and water within a hydrogel. Raza stated, "In pure water, you don't find many water clusters near the surface—where evaporation can take place. But there are lots of water clusters in the second model, because they form where the water comes into contact with the hydrogel. Because there are more water clusters near the surface in the second model, evaporation happens more quickly. Basically, there are more water clusters that the oscillating field can cleave off from the liquid water."

This groundbreaking research not only advances the understanding of solar-induced evaporation but also has implications for engineering more efficient water-evaporation technologies. Liu emphasized the significance of this work, saying, "This work substantially advances our understanding of what's taking place in this phenomenon, since we are the first to show the role of the water clusters via computational simulation."

The study was co-authored by Cong Yang, a Ph.D. graduate from NC State, and Xin Qian, a co-corresponding author from the Huazhong University of Science and Technology. As the research community continues to delve into the efficiency of sunlight in evaporation processes, the findings from this study may pave the way for innovative applications in water management and purification technologies.

For further details, refer to the original paper published in *Materials Horizons* (2025), DOI: 10.1039/D5MH00353A.