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ACS Nano

Title:		Atmosphere-Mediated Superhydrophobicity of Rationally Designed Micro/Nanostructured Surfaces
Author(s):		Yan X; Huang Z; Sett S; Oh J; Cha H; Li L; Feng L; Wu Y; Zhao C; Orejon D; Chen F; Miljkovic N;
Address:		"Institute of Nuclear and New Energy Technology , Tsinghua University , Beijing 100084 , China. International Institute for Carbon Neutral Energy Research (WPI-I2CNER) , Kyushu University , 744 Moto-oka , Nishi-ku , Fukuoka 819-0395 , Japan. Institute for Multiscale Thermofluids, School of Engineering , The University of Edinburgh , King's Buildings, Edinburgh EH9 3FD , United Kingdom"
Journal Title:		ACS Nano
Year:		2019
Volume:		20190408
Issue:		4
Page Number:		4160 - 4173
DOI:		10.1021/acsnano.8b09106
ISSN/ISBN:		1936-086X (Electronic) 1936-0851 (Linking)
Abstract:		"Superhydrophobicity has received significant attention over the past three decades owing to its significant potential in self-cleaning, anti-icing and drag reduction surfaces, energy-harvesting devices, antibacterial coatings, and enhanced heat transfer applications. Superhydrophobicity can be obtained via the roughening of an intrinsically hydrophobic surface, the creation of a re-entrant geometry, or by the roughening of a hydrophilic surface followed by a conformal coating of a hydrophobic material. Intrinsically hydrophobic surfaces have poor thermophysical properties, such as thermal conductivity, and thus are not suitable for heat transfer applications. Re-entrant geometries, although versatile in applications where droplets are deposited, break down during spatially random nucleation and flood the surface. Chemical functionalization of rough metallic substrates, although promising, is not utilized because of the poor durability of conformal hydrophobic coatings. Here we develop a radically different approach to achieve stable superhydrophobicity. By utilizing laser processing and thermal oxidation of copper (Cu) to create a high surface energy hierarchical copper oxide (CuO), followed by repeatable and passive atmospheric adsorption of hydrophobic volatile organic compounds (VOCs), we show that stable superhydrophobicity with apparent advancing contact angles approximately 160 degrees and contact angle hysteresis as low as approximately 20 degrees can be achieved. We exploit the structure length scale and structure geometry-dependent VOC adsorption dynamics to rationally design CuO nanowires with enhanced superhydrophobicity. To gain an understanding of the VOC adsorption physics, we utilized X-ray photoelectron and ion mass spectroscopy to identify the chemical species deposited on our surfaces in two distinct locations: Urbana, IL, United States and Beijing, China. To test the stability of the atmosphere-mediated superhydrophobic surfaces during heterogeneous nucleation, we used high-speed optical microscopy to demonstrate the occurrence of dropwise condensation and stable coalescence-induced droplet jumping. Our work not only provides rational design guidelines for developing passively durable superhydrophobic surfaces with excellent flooding-resistance and self-healing capability but also sheds light on the key role played by the atmosphere in governing wetting"
Keywords:		adsorption coalescence-induced droplet jumping condensation heat transfer nanostructure superhydrophobic volatile organic compounds wetting;
Notes:		"PubMed-not-MEDLINEYan, Xiao Huang, Zhiyong Sett, Soumyadip Oh, Junho Cha, Hyeongyun Li, Longnan Feng, Lezhou Wu, Yifan Zhao, Chongyan Orejon, Daniel Chen, Feng Miljkovic, Nenad eng 2019/04/02 ACS Nano. 2019 Apr 23; 13(4):4160-4173. doi: 10.1021/acsnano.8b09106. Epub 2019 Apr 8"