Spontaneous Marangoni Mixing of Miscible Liquids at a Liquid–Liquid–Air Contact Line

Kim, Hyoungsoo; Lee, Jeongsu; Kim, Tae-Hong; Kim, Ho-Young

doi:10.1021/acs.langmuir.5b01897

Cited by 34 publications

(23 citation statements)

References 26 publications

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“…Therefore, the spreading distance in figure 7 is enhanced for the measurements by Joos & Van Hunsel (1985); Berg (2009);Huh et al (1975) and Camp & Berg (1987). As discussed, constants a ≈ 0.88 and a ≈ 0.3 were reported for immiscible (Dussaud & Troian 1998) and miscible (Santiago-Rosanne et al 2001;Kim et al 2015) liquids, respectively. The lower value was attributed to liquid densification by dissolution, which results in vortex formation by gravitational "sinking" of the heavier liquid (Santiago-Rosanne et al 2001).…”

Section: Resultsmentioning

confidence: 75%

Marangoni-driven spreading of miscible liquids in the binary pendant drop geometry

et al. 2019

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When two liquids with different surface tensions come into contact, the liquid with lower surface tension spreads over the other. This Marangoni-driven spreading has been studied for various geometries and surfactants, but the dynamics of the binary geometry (drop-drop) has hardly been quantitatively investigated, despite its relevance for drop encapsulation applications. Here we use laser-induced fluorescence (LIF) to temporally resolve the distance L(t) over which a low-surface-tension drop spreads over a miscible high-surface-tension drop. L(t) is measured for various surface tension differences between the liquids and for various viscosities, revealing a power-law L(t) ∼ t α with a spreading exponent α ≈ 0.75. This value is consistent with previous results for viscosity-limited spreading over a deep bath. A single power law of rescaled distance as a function of rescaled time reasonably captures our experiments, as well as different geometries, miscibilities, and surface tension modifiers (solvents and surfactants). This result enables engineering the spreading dynamics of a wide range of liquid-liquid systems.

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Section: Resultsmentioning

confidence: 75%

Marangoni-driven spreading of miscible liquids in the binary pendant drop geometry

et al. 2019

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“…We finally get the spreading energy as ED∼μaRdUdRea1/2Red3/4 by substituting Rm and Ūc as derived in SI Appendix , section E. The rotational energy of the air vortex, ER, is given as ρanormalΓ2(t≈0)=ρatruer¯w2(truer¯ww¯)2 (24), where truer¯w and w¯ are the mean radius and vorticity of the air vortex, respectively. By balancing spreading and rotational energies, we get the circulation asnormalΓ(t≈0)∼Re…”

Section: Resultsmentioning

confidence: 99%

Vortex-induced dispersal of a plant pathogen by raindrop impact

Kim

Park

Gruszewski

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Raindrop impact on infected plants can disperse micron-sized propagules of plant pathogens (e.g., spores of fungi). Little is known about the mechanism of how plant pathogens are liberated and transported due to raindrop impact. We used high-speed photography to observe thousands of dry-dispersed spores of the rust fungus Puccinia triticina being liberated from infected wheat plants following the impact of a single raindrop. We revealed that an air vortex ring was formed during the raindrop impact and carried the dry-dispersed spores away from the surface of the host plant. The maximum height and travel distance of the airborne spores increased with the aid of the air vortex. This unique mechanism of vortex-induced dispersal dynamics was characterized to predict trajectories of spores. Finally, we found that the spores transported by the air vortex can reach beyond the laminar boundary layer of leaves, which would enable the long-distance transport of plant pathogens through the atmosphere.

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“…For example, for the soluble surfactant spreading case, the velocity profile shows a power-law behaviour 14 , u ∼ r −1/3 where γ is constant at the leading edge. For the miscible liquids spreading case, an understanding of the spreading and mixing mechanism is still lacking, although particular mixing features were captured 19,20 . Therefore, to understand this case, we performed many different …”

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confidence: 99%

Solutal Marangoni flows of miscible liquids drive transport without surface contamination

et al. 2017

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Mixing and spreading of di erent liquids are omnipresent in nature, life and technology, such as oil pollution on the sea 1,2 , estuaries 3 , food processing 4 , cosmetic and beverage industries 5,6 , lab-on-a-chip devices 7 , and polymer processing 8 . However, the mixing and spreading mechanisms for miscible liquids remain poorly characterized. Here, we show that a fully soluble liquid drop deposited on a liquid surface remains as a static lens without immediately spreading and mixing, and simultaneously a Marangoni-driven convective flow is generated, which are counterintuitive results when two liquids have di erent surface tensions. To understand the dynamics, we develop a theoretical model to predict the finite spreading time and length scales, the Marangoni-driven convection flow speed, and the finite timescale to establish the quasi-steady state for the Marangoni flow. The fundamental understanding of this solutal Marangoni flow may enable driving bulk flows and constructing an e ective drug delivery and surface cleaning approach without causing surface contamination by immiscible chemical species.When a sessile oil drop is released on top of a water surface, it spreads until a monolayer is achieved 9 , because the liquids are immiscible, as shown in Fig. 1a. In contrast, if a water drop is placed on a water surface, it shows a cascade of coalescence events and the liquids are rapidly mixed (Fig. 1b) 10 . In contrast with these two configurations, we captured unexpected mixing and spreading features between fully miscible liquids. When a drop of alcoholfor example, isopropanol (IPA)-is placed on a water surface, it spontaneously generates a Marangoni convective flow along the outward radial direction and we observed that there is a static liquid lens in the middle ( Fig. 1c and Supplementary Fig. 1), even though these two liquids are infinitely miscible. Here, we discuss solutal Marangoni effects in fully miscible liquids to explain the finite size lens and the associated flow (more details are provided in Supplementary Videos 1-3).To visualize the spreading and mixing pattern of a miscible liquid drop, IPA (volume V = 7.2 ± 0.2 µl), placed on a water bath (400 ml deionized (DI) water in an 196-mm-diameter Petri dish with depth H = 14 mm), we used time-resolved particle tracking velocimetry (PTV) and high-speed schlieren measurement techniques (Supplementary Information). For PTV experiments, we seeded polystyrene particles (diameter = 100 µm) in solution and recorded the particle motion from top and side views. IPA is less dense than water and therefore the sessile drop floats on the surface. The drop initially spreads out and quickly achieves a static central lens with a near constant diameter 2R (see Fig. 1c and Supplementary Figs 5-7) during which the IPA continuously leaks at the boundary (Fig. 1c, Supplementary Fig. 1 and Supplementary Videos 3 and 4). The inset of Fig. 2a shows a top view of a schlieren pattern, that is, an interfacial turbulence structure representing the mass transfer between the...

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Spontaneous Marangoni Mixing of Miscible Liquids at a Liquid–Liquid–Air Contact Line

Cited by 34 publications

References 26 publications

Marangoni-driven spreading of miscible liquids in the binary pendant drop geometry

Marangoni-driven spreading of miscible liquids in the binary pendant drop geometry

Vortex-induced dispersal of a plant pathogen by raindrop impact

Solutal Marangoni flows of miscible liquids drive transport without surface contamination

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