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).   

The McKelvey School of Engineering at Washington University in St. Louis promotes independent inquiry and education with an emphasis on scientific excellence, innovation and collaboration without boundaries. McKelvey Engineering has top-ranked research and graduate programs across departments, particularly in biomedical engineering, environmental engineering and computing, and has one of the most selective undergraduate programs in the country. With 165 full-time faculty, 1,420 undergraduate students, 1,614 graduate students and 21,000 living alumni, we are working to solve some of society’s greatest challenges; to prepare students to become leaders and innovate throughout their careers; and to be a catalyst of economic development for the St. Louis region and beyond.

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