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Title: Hierarchical Superhydrophobic Surfaces with Micropatterned Nanowire Arrays for High-Efficiency Jumping Droplet Condensation

Abstract

Self-propelled droplet jumping on nanostructured superhydrophobic surfaces is of interest for a variety of industrial applications including self-cleaning, water harvesting, power generation, and thermal management systems. However, the uncontrolled nucleation-induced Wenzel state of condensed droplets at large surface subcooling (high heat flux) leads to the formation of unwanted large pinned droplets, which results in the flooding phenomenon and greatly degrades the heat transfer performance. In this work, we present a novel strategy to manipulate droplet behaviors during the process from the droplet nucleation to growth and departure through a combination of spatially controlling initial nucleation for mobile droplets by closely spaced nanowires and promoting the spontaneous outward movement of droplets for rapid removal using micropatterned nanowire arrays. Through the optical visualization experiments and heat transfer tests, we demonstrate greatly improved condensation heat transfer characteristics on the hierarchical superhydrophobic surface including the higher density of microdroplets, smaller droplet departure radius, 133% wider range of surface subcooling for droplet jumping, and 37% enhancement in critical heat flux for jumping droplet condensation, compared to the-state-of-art jumping droplet condensation on nanostructured superhydrophobic surfaces. The excellent water repellency of such hierarchical superhydrophobic surfaces can be promising for many potential applications, such as anti-icing, antifogging, watermore » desalination, and phase-change heat transfer.« less

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [2]; ORCiD logo [3]
  1. Univ. of Colorado, Boulder, CO (United States)
  2. Dalian Univ. of Technology (China)
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1415123
Report Number(s):
NREL/JA-5500-70721
Journal ID: ISSN 1944-8244; TRN: US1800757
Grant/Contract Number:  
AC36-08GO28308
Resource Type:
Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 9; Journal Issue: 51; Journal ID: ISSN 1944-8244
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; condensation; hierarchical nanostructured surface; jumping droplets; nucleation control; spontaneous droplet movement; superhydrophobic

Citation Formats

Wen, Rongfu, Xu, Shanshan, Zhao, Dongliang, Lee, Yung-Cheng, Ma, Xuehu, and Yang, Ronggui. Hierarchical Superhydrophobic Surfaces with Micropatterned Nanowire Arrays for High-Efficiency Jumping Droplet Condensation. United States: N. p., 2017. Web. doi:10.1021/acsami.7b14960.
Wen, Rongfu, Xu, Shanshan, Zhao, Dongliang, Lee, Yung-Cheng, Ma, Xuehu, & Yang, Ronggui. Hierarchical Superhydrophobic Surfaces with Micropatterned Nanowire Arrays for High-Efficiency Jumping Droplet Condensation. United States. doi:10.1021/acsami.7b14960.
Wen, Rongfu, Xu, Shanshan, Zhao, Dongliang, Lee, Yung-Cheng, Ma, Xuehu, and Yang, Ronggui. Thu . "Hierarchical Superhydrophobic Surfaces with Micropatterned Nanowire Arrays for High-Efficiency Jumping Droplet Condensation". United States. doi:10.1021/acsami.7b14960. https://www.osti.gov/servlets/purl/1415123.
@article{osti_1415123,
title = {Hierarchical Superhydrophobic Surfaces with Micropatterned Nanowire Arrays for High-Efficiency Jumping Droplet Condensation},
author = {Wen, Rongfu and Xu, Shanshan and Zhao, Dongliang and Lee, Yung-Cheng and Ma, Xuehu and Yang, Ronggui},
abstractNote = {Self-propelled droplet jumping on nanostructured superhydrophobic surfaces is of interest for a variety of industrial applications including self-cleaning, water harvesting, power generation, and thermal management systems. However, the uncontrolled nucleation-induced Wenzel state of condensed droplets at large surface subcooling (high heat flux) leads to the formation of unwanted large pinned droplets, which results in the flooding phenomenon and greatly degrades the heat transfer performance. In this work, we present a novel strategy to manipulate droplet behaviors during the process from the droplet nucleation to growth and departure through a combination of spatially controlling initial nucleation for mobile droplets by closely spaced nanowires and promoting the spontaneous outward movement of droplets for rapid removal using micropatterned nanowire arrays. Through the optical visualization experiments and heat transfer tests, we demonstrate greatly improved condensation heat transfer characteristics on the hierarchical superhydrophobic surface including the higher density of microdroplets, smaller droplet departure radius, 133% wider range of surface subcooling for droplet jumping, and 37% enhancement in critical heat flux for jumping droplet condensation, compared to the-state-of-art jumping droplet condensation on nanostructured superhydrophobic surfaces. The excellent water repellency of such hierarchical superhydrophobic surfaces can be promising for many potential applications, such as anti-icing, antifogging, water desalination, and phase-change heat transfer.},
doi = {10.1021/acsami.7b14960},
journal = {ACS Applied Materials and Interfaces},
number = 51,
volume = 9,
place = {United States},
year = {2017},
month = {12}
}

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Cited by: 15 works
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Figures / Tables:

Figure 1 Figure 1: Design of the hierarchical superhydrophobic surface with micropatterned nanowire arrays for the nucleation control and rapid departure of condensed droplets. (a) Schematic showing the closely spaced nanowires for controlling initial nucleation to be only on the top surface of nanowire arrays, i.e., reducing the density of water vapormore » in the separations between nanowires and thus inhibiting nucleation due to the lower vapor density, ρin > ρout. (b) Microvalleys between long nanowire arrays for the spontaneous outward movement of growing droplets by the outward Laplace pressure, ΔP = Pup − Pdown, which is attributed to the deformation of the growing droplet by the confinement of microvalleys, R1 < R2. (c) SEM images of the hierarchical nanowired superhydrophobic surface consisting of micropatterns of long nanowire arrays surrounded by short nanowires, which forms the microvalleys. Insets are the magnified view of closely spaced short nanowire arrays (yellow dash rectangle) and long nanowire arrays (red dash rectangle). (d) The apparent contact angle 167 ± 3° of a 5 μL water droplet on the hierarchical nanowired superhydrophobic surface.« less

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Works referencing / citing this record:

Fundamentals of icing and common strategies for designing biomimetic anti-icing surfaces
journal, January 2018

  • Li, Qi; Guo, Zhiguang
  • Journal of Materials Chemistry A, Vol. 6, Issue 28
  • DOI: 10.1039/c8ta03259a

    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.