Evaporation kinetics of sessile water droplets on micropillared superhydrophobic surfaces

Wei Xu, Rajesh Leeladhar, Yong Tae Kang, Chang Hwan Choi

Research output: Contribution to journalArticle

76 Citations (Scopus)

Abstract

Evaporation modes and kinetics of sessile droplets of water on micropillared superhydrophobic surfaces are experimentally investigated. The results show that a constant contact radius (CCR) mode and a constant contact angle (CCA) mode are two dominating evaporation modes during droplet evaporation on the superhydrophobic surfaces. With the decrease in the solid fraction of the superhydrophobic surfaces, the duration of a CCR mode is reduced and that of a CCA mode is increased. Compared to Rowan's kinetic model, which is based on the vapor diffusion across the droplet boundary, the change in a contact angle in a CCR (pinned) mode shows a remarkable deviation, decreasing at a slower rate on the superhydrophobic surfaces with less-solid fractions. In a CCA (receding) mode, the change in a contact radius agrees well with the theoretical expectation, and the receding speed is slower on the superhydrophobic surfaces with lower solid fractions. The discrepancy between experimental results and Rowan's model is attributed to the initial large contact angle of a droplet on superhydrophobic surfaces. The droplet geometry with a large contact angle results in a narrow wedge region of air along the contact boundary, where the liquid-vapor diffusion is significantly restricted. Such an effect becomes minor as the evaporation proceeds with the decrease in a contact angle. In both the CCR and CCA modes, the evaporative mass transfer shows the linear relationship between mass2/3 and evaporation time. However, the evaporation rate is slower on the superhydrophobic surfaces, which is more significant on the surfaces with lower solid fractions. As a result, the superhydrophobic surfaces slow down the drying process of a sessile droplet on them.

Original languageEnglish
Pages (from-to)6032-6041
Number of pages10
JournalLangmuir
Volume29
Issue number20
DOIs
Publication statusPublished - 2013 May 21
Externally publishedYes

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Sorbus
Evaporation
Contact angle
evaporation
Kinetics
Water
kinetics
Contacts (fluid mechanics)
water
Air
radii
Vapors
vapors
evaporation rate
wedges
drying
mass transfer
Drying
Mass transfer

ASJC Scopus subject areas

  • Electrochemistry
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Materials Science(all)
  • Spectroscopy

Cite this

Evaporation kinetics of sessile water droplets on micropillared superhydrophobic surfaces. / Xu, Wei; Leeladhar, Rajesh; Kang, Yong Tae; Choi, Chang Hwan.

In: Langmuir, Vol. 29, No. 20, 21.05.2013, p. 6032-6041.

Research output: Contribution to journalArticle

Xu, Wei ; Leeladhar, Rajesh ; Kang, Yong Tae ; Choi, Chang Hwan. / Evaporation kinetics of sessile water droplets on micropillared superhydrophobic surfaces. In: Langmuir. 2013 ; Vol. 29, No. 20. pp. 6032-6041.
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