Coalescence-induced droplet jumping on atmospheric-mediated superhydrophobic surfaces

Xiao Yan, Feng Chen, Soumyadip Sett, Lezhou Feng, Junho Oh, Hyeongyun Cha, Longnan Li, Zhiyong Huang, Nenad Miljkovic

Research output: Contribution to journalConference articlepeer-review


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.

Original languageEnglish (US)
Pages (from-to)2333-2340
Number of pages8
JournalInternational Heat Transfer Conference
StatePublished - 2018
Event16th International Heat Transfer Conference, IHTC 2018 - Beijing, China
Duration: Aug 10 2018Aug 15 2018


  • Coalescence-induced droplet jumping
  • Coatless Superhydrophobicity
  • Condensation
  • Hydrocarbons
  • Manufacturing
  • Nano/Micro
  • VOCs
  • Volatile Organic Compounds

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanical Engineering
  • Fluid Flow and Transfer Processes


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