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Nonisothermal Spreading Dynamics of Self-Rewetting Droplets

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https://pubs.acs.org/doi/10.1021/acs.langmuir.7b04045
Original languageEnglish
Pages (from-to)1916–1931
Number of pages16
JournalLangmuir
Volume34
Issue number5
Early online date16 Jan 2018
DOIs
Publication statusPublished - 6 Feb 2018

Abstract

We experimentally studied the spreading dynamics of binary alcohol mixtures (and pure liquids for reference) deposited on a heated substrate in a partially wetting situation, under non-isothermal conditions. We show that the spreading mechanism of an evaporating droplet exhibits a power law growth with early-stage exponents that depend strongly and non-monotonically on substrate temperature. Moreover, we investigated the temporal and spatial thermal dynamics in the droplet using infrared thermography revealing the existence of unique thermal patterns due to thermal and/or solutal instabilities which lead to surface tension gradients, namely Marangoni effect. Our key findings are that the temperature of the substrate drastically affects the early-stage inertial-capillary spreading regime owing to the non-monotonic surface tension/temperature dependence of the self-rewetting liquids. At later stages of wetting, the spreading dynamics enters the viscous-capillary dominated regime with the characteristic low kinetics mirroring the behavior of pure liquids.

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