A team led by Patricia Weisensee, assistant professor of mechanical engineering & materials science at the McKelvey School of Engineering at Washington University in St. Louis, found that nucleation – initial step to change from a vapor to a liquid state — is heavily influenced by the dynamics of a microscopically uneven oil film during water condensation on lubricant-infused surfaces that are often used in micro- and nanoscale research. Results of the research were published in Langmuir Oct. 26, 2021.
Weisensee; Jianxing Sun, a doctoral student in Weisensee’s lab and first author on the paper; and Xinyu Jiang, who earned a master’s degree in mechanical engineering from the McKelvey School of Engineering in 2020, used high-speed, high-resolution optical and infrared imaging to “count droplets” and to compare the oil-vapor interface temperature between regions with a relatively thicker (oil-rich) and relatively thinner (oil-poor) layer of oil. They found up to 3 K lower temperature on oil-poor surface regions, which decrease the nucleation energy barrier by up to an order of magnitude. The oil film continuously redistributes as a result of self-propulsion of the condensed microdroplets, leading to a constant high nucleation rate on the lubricant-infused surfaces, compared with solid surfaces, on which nucleation is sporadic.
“Our findings shed new light on dynamic water-lubricant interactions and provide new design rationales for choosing surfaces for enhanced dropwise condensation and water collection efficiencies,” Sun said.
Sun J, Jiang X, Weisensee PB. Enhanced Water Nucleation and Growth Based on Microdroplet Mobility on Lubricant-Infused Surfaces. Langmuir, Oct. 26, 2021. DOI: 10.1021/acs.langmuir.1c01559
The research was supported with funding from the National Science Foundation (1856722).