The effect of dynamic wetting pressure on contact angle measurements.

Autor: Ahmed A; interfacial Science and Surface Engineering Lab (iSSELab), Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G2G8, Canada., Sanedrin R; KRÜSS USA, 1020 Crews Rd K, Mathhews, NC 28105, United States., Willers T; KRÜSS GmbH, Borsteler Chaussee 85, 22453 Hamburg, Germany. Electronic address: T.Willers@kruss.de., Waghmare PR; interfacial Science and Surface Engineering Lab (iSSELab), Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G2G8, Canada. Electronic address: waghmare@ualberta.ca.
Jazyk: angličtina
Zdroj: Journal of colloid and interface science [J Colloid Interface Sci] 2022 Feb 15; Vol. 608 (Pt 1), pp. 1086-1093. Date of Electronic Publication: 2021 Oct 08.
DOI: 10.1016/j.jcis.2021.10.003
Abstrakt: Hypothesis: The drop deposition technique can impact contact angle measurements. We hypothesized that the drop pinch-off, during the traditionally used pendant drop technique, significantly alters the static contact angle. The capillary waves and dynamic wetting pressure generated during the pendant drop deposition are the source for forced spreading, which can be circumvented by alternative liquid-needle drop deposition techniques.
Experiments: To compare the role of drop pinch-off and resultant dynamic wetting pressure, we meticulously observed and quantified the entire drop deposition process using high speed imaging until the drop attains the static contact angle in both cases, namely pendant drop and liquid needle deposition technique. Conventionally used standard substrates are compared using both techniques and further compared using literature data. The capillary waves and corresponding drop shape variations are analysed for quantifying the dynamic wetting pressure by measuring drop base diameter, contact angle and centre of mass.
Findings: We compared three parameters - drop pinch-off, spreading behaviour and respective static contact angles along with the resultant dynamic wetting pressure for both the techniques, i.e., pendant drop and liquid-needle. For the pendant drop technique we observed a pronounced drop volume dependency of these parameters even though the corresponding Bond numbers are less than unity. In contrast, for the liquid needle there is no such dependency. With a theoretical argument corroborating experimental observations, this work highlights the importance of a well controlled drop deposition, with a minimum wetting pressure, in order to guarantee contact angle data that is independent of drop deposition effects, thereby only reflecting the substrate properties.
Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [TW and RS are employed by KRÜSS GmbH and KRÜSS USA, respectively.]
(Copyright © 2021 Elsevier Inc. All rights reserved.)
Databáze: MEDLINE
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