Condensation of Satellite Droplets on Lubricant-Cloaked Droplets

Qiaoyu Ge, Aikifa Raza, Hongxia Li, Soumyadip Sett, Nenad Miljkovic, Tiejun Zhang

Research output: Contribution to journalArticlepeer-review

Abstract

Condensation on lubricant-infused micro- or nanotextured superhydrophobic surfaces exhibits remarkable heat transfer performance owing to the high condensation nucleation density and efficient condensate droplet removal. When a low surface tension lubricant is used, it can spread on the condensed droplet and "cloak" it. Here, we describe a previously unobserved condensation phenomenon of satellite droplet formation on lubricant-cloaked water droplets using environmental scanning electron microscopy. The presence of satellite droplets confirms the cloaking behavior of common lubricants on water such as Krytox oils. More interestingly, we have observed satellite droplets on BMIm ionic liquid-infused surfaces, which is unexpected because BMIm was used in previous reports as a lubricant to eliminate cloaking during water condensation. Our studies reveal that the cloaking of BMIm on water droplets is theoretically favorable due to the fast timescale spreading during initial condensation when compared to the long timescale required for dissolution of the lubricant in water. We utilize a novel characterization approach based on Raman spectroscopy to confirm the existence of cloaking lubricant films on water droplets residing on lubricant-infused surfaces. The selected lubricants include Krytox oil, ionic liquid, and dodecane, which have drastically different surface tensions and polarities. In addition, spreading dynamics of cloaking and noncloaking lubricants on water droplets show that ionic liquid has the capability to mobilize water droplets spontaneously owing to cloaking and its relatively high surface tension. Our studies not only elucidate the physics governing cloaking and satellite droplet condensation phenomena at micro- and macroscales but also reveal a subset of previously unobserved lubricant-water interfacial interactions for a large variety of applications.

Original languageEnglish (US)
Pages (from-to)22246-22255
Number of pages10
JournalACS Applied Materials and Interfaces
Volume12
Issue number19
DOIs
StatePublished - May 13 2020

Keywords

  • cloaking
  • dropwise condensation
  • ionic liquid
  • lubricant-infused surface
  • satellite droplets

ASJC Scopus subject areas

  • Materials Science(all)

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