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Coalescence and Noncoalescence of Sessile Drops : Impact of Surface Forces

Title data

Karpitschka, Stefan ; Hanske, Christoph ; Fery, Andreas ; Riegler, Hans:
Coalescence and Noncoalescence of Sessile Drops : Impact of Surface Forces.
In: Langmuir. Vol. 30 (June 2014) Issue 23 . - pp. 6826-6830.
ISSN 1520-5827
DOI: https://doi.org/10.1021/la500459v

Official URL: Volltext

Abstract in another language

Due to capillarity, sessile droplets of identical liquids will instantaneously fuse when they come in contact at their three-phase lines. However, with drops of different, completely miscible liquids, instantaneous coalescence can be suppressed. Instead, the drops remain in a state of noncoalescence for some time, with the two drop bodies connected only by a thin neck. The reason for this noncoalescence is the surface tension difference, Δγ, between the liquids. If Δγ is sufficiently large, then it induces a sufficiently strong Marangoni flow, which keeps the main drop bodies temporarily separated. Studies with spreading drops have revealed that the boundary between instantaneous coalescence and noncoalescence is sharp (Karpitschka, S.; Riegler, H. J. Fluid. Mech. 2014, 743, R1). The boundary is a function of two parameters only: Δγ and Θ̅a, the arithmetic mean of the contact angles in the moment of drop−drop contact. It appears plausible that surface forces (the disjoining pressure) could also influence the coalescence behavior. However, in experiments with spreading drops, surface forces always promote coalescence and their influence might be obscured. Therefore, we present here coalescence experiments with partially wetting liquids and compare the results to the spreading case. We adjust different equilibrium contact angles (i.e., different surface forces) with different substrate surface coatings. As for spreading drops, we observe a sharp boundary between regimes of coalescence and noncoalescence. The boundary follows the same power law relation for both partially and completely wetting cases. Therefore, we conclude that surface forces have no significant, explicit influence on the coalescence behavior of sessile drops from different miscible liquids.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Former Professors > Chair Physical Chemistry II - Univ.-Prof. Dr. Andreas Fery
Research Institutions > Collaborative Research Centers, Research Unit > SFB 840 Von partikulären Nanosystemen zur Mesotechnologie
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Physical Chemistry II
Research Institutions
Research Institutions > Collaborative Research Centers, Research Unit
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Former Professors
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 500 Natural sciences
500 Science > 530 Physics
500 Science > 540 Chemistry
Date Deposited: 05 Dec 2014 09:49
Last Modified: 05 Dec 2014 09:49
URI: https://eref.uni-bayreuth.de/id/eprint/3925