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Wetting and Drying of Aqueous Droplets Containing Nonionic Surfactants CnEm

Shi, Jing; Yang, Lisong; Bain, Colin D.

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Jing Shi


This paper presents a systematic study of the wetting and drying of aqueous pico-liter droplets containing nonionic surfactants polyoxyethylene alkyl ethers (CnEm; n = 10, 12, 14, m = 6 or 8) in comparison with the anionic surfactant sodium dodecyl sulfate (SDS). The spreading and drying of droplets on hydrophilic substrates were studied by tracking the three-phase contact line (TCL) and by interferometry. CnEm droplets undergo phase separation during drying: a water-rich droplet retracts and leaves behind a thin film that is postulated to be a surfactant mesophase. This thin film either retracts or breaks up into small droplets on a longer time scale. The receding contact angle of the water-rich droplet on the thin film in the late stage of drying of CnEm droplets is independent of hydrophobicity of substrates, supporting the inference that a mesophase is present on the surface. Both CnEm and SDS solutions inhibit spreading on hydrophilic surfaces, which is attributed to Marangoni contraction as a result of a surface tension gradient across the gas–liquid interface. More pronounced suppression of spreading is observed in the case of CnEm solutions, possibly due to the phase transition of surfactant solution in the vicinity of the initial TCL leading to a viscous phase at the TCL that pins the droplet. Tracer particle measurements reveal that mild Marangoni flows exist for droplets with surfactant concentrations well above the critical micelle concentration (CMC). Origins of the surfactant gradients that result in Marangoni flows are discussed.


Shi, J., Yang, L., & Bain, C. D. (2021). Wetting and Drying of Aqueous Droplets Containing Nonionic Surfactants CnEm. Langmuir, 37(14), 4091-4101.

Journal Article Type Article
Online Publication Date Apr 2, 2021
Publication Date Apr 13, 2021
Deposit Date Sep 6, 2021
Publicly Available Date Apr 2, 2022
Journal Langmuir
Print ISSN 0743-7463
Electronic ISSN 1520-5827
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 37
Issue 14
Pages 4091-4101
Public URL


Accepted Journal Article (1.5 Mb)

Copyright Statement
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Langmuir, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see

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