TY - JOUR
T1 - Coalescence-induced droplet jumping on atmospheric-mediated superhydrophobic surfaces
AU - Yan, Xiao
AU - Chen, Feng
AU - Sett, Soumyadip
AU - Feng, Lezhou
AU - Oh, Junho
AU - Cha, Hyeongyun
AU - Li, Longnan
AU - Huang, Zhiyong
AU - Miljkovic, Nenad
N1 - Funding Information:
The authors gratefully acknowledge the funding support from the Office of Naval Research (ONR) (Grant No. N00014-16-1-2625), and the National Science Foundation under Award No. 1554249. X.Y, F.C, and Z.H gratefully acknowledge funding support from the National Natural Science Foundation of China (Grant No. 51206092) and National Science and Technology Major Project (ZX06901). X.Y. appreciates the financial support of China Scholarship Council (Grant No. 201606210181). X.Y. especially appreciates Xueqian Zhang and Gengyu Zhang in Tsinghua University, for their kind help in surface fabrication. N.M. gratefully acknowledges funding support from the International Institute for Carbon Neutral Energy Research (WPI-I2CNER), sponsored by the Japanese Ministry of Education, Culture, Sports, Science and Technology. SEM and XPS analysis were carried out at the Frederick Seitz Materials Research Laboratory at the University of Illinois.
Publisher Copyright:
© 2018 International Heat Transfer Conference. All rights reserved.
PY - 2018
Y1 - 2018
N2 - Coalescence-induced droplet jumping has received much attention over the past decade due to its ability to passively remove microscale droplets thereby enhancing condensation heat transfer, anti-icing, self-cleaning, and energy harvesting performance. However, droplet-jumping relies on surface superhydrophobicity, which results from the joint contributions of surface roughness and low-surface-energy conformal coatings such as alkyl and perfluorinated molecules. In spite of fantastic laboratory scale demonstrations, jumping-droplet surfaces fail to gain traction in real-life applications due to poor durability of the low surface energy coatings required to achieve superhydrophobicity. Here, we demonstrate that by exposing rationally designed intrinsically hydrophilic copper-based hierarchically structured CuO surfaces to ambient air, robust superhydrophobicity enabling coalescence-induced droplet jumping can be achieved. The as-prepared CuO surfaces experienced a transition from superhydrophilic to superhydrophobic with final apparent advancing contact angle and roll-off angle of >160° and <10°, respectively. X-ray photoelectron spectroscopy (XPS) confirmed that the wettability transition from wetting to non-wetting arises due to adsorption of airborne volatile organic compounds (VOCs) on the high-aspect-ratio and high-surface-area nanostructures. Due to the permanent and reliable source of VOCs in ambient air, the superhydrophobicity was shown to be retrievable after organic solvent and plasma cleaning. Most importantly, high-speed optical microscopy revealed the presence of stable coalescence-induced droplet jumping during atmospheric water vapor condensation. Our work not only promises an economic and facile way of fabricating superhydrophobic surfaces without the need for application of low-surface-energy chemistries, it also develops a platform for the development of next-generation durable superhydrophobic surfaces that can self-heal in the presence of ambient air.
AB - Coalescence-induced droplet jumping has received much attention over the past decade due to its ability to passively remove microscale droplets thereby enhancing condensation heat transfer, anti-icing, self-cleaning, and energy harvesting performance. However, droplet-jumping relies on surface superhydrophobicity, which results from the joint contributions of surface roughness and low-surface-energy conformal coatings such as alkyl and perfluorinated molecules. In spite of fantastic laboratory scale demonstrations, jumping-droplet surfaces fail to gain traction in real-life applications due to poor durability of the low surface energy coatings required to achieve superhydrophobicity. Here, we demonstrate that by exposing rationally designed intrinsically hydrophilic copper-based hierarchically structured CuO surfaces to ambient air, robust superhydrophobicity enabling coalescence-induced droplet jumping can be achieved. The as-prepared CuO surfaces experienced a transition from superhydrophilic to superhydrophobic with final apparent advancing contact angle and roll-off angle of >160° and <10°, respectively. X-ray photoelectron spectroscopy (XPS) confirmed that the wettability transition from wetting to non-wetting arises due to adsorption of airborne volatile organic compounds (VOCs) on the high-aspect-ratio and high-surface-area nanostructures. Due to the permanent and reliable source of VOCs in ambient air, the superhydrophobicity was shown to be retrievable after organic solvent and plasma cleaning. Most importantly, high-speed optical microscopy revealed the presence of stable coalescence-induced droplet jumping during atmospheric water vapor condensation. Our work not only promises an economic and facile way of fabricating superhydrophobic surfaces without the need for application of low-surface-energy chemistries, it also develops a platform for the development of next-generation durable superhydrophobic surfaces that can self-heal in the presence of ambient air.
KW - Coalescence-induced droplet jumping
KW - Coatless Superhydrophobicity
KW - Condensation
KW - Hydrocarbons
KW - Manufacturing
KW - Nano/Micro
KW - VOCs
KW - Volatile Organic Compounds
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U2 - 10.1615/ihtc16.cod.022157
DO - 10.1615/ihtc16.cod.022157
M3 - Conference article
AN - SCOPUS:85060381379
VL - 2018-August
SP - 2333
EP - 2340
JO - International Heat Transfer Conference
JF - International Heat Transfer Conference
SN - 2377-424X
T2 - 16th International Heat Transfer Conference, IHTC 2018
Y2 - 10 August 2018 through 15 August 2018
ER -