Mixed mode of dissolving immersed nanodroplets at a solid–water interface

Zhang, Xuehua; Wang, Jun; Bao, Lei; Dietrich, Erik; Veen, Roeland van der; Peng, Shuhua; Friend, James; Zandvliet, Henricus J.W.; Yeo, Leslie; Lohse, Detlef

doi:10.1039/c4sm02397h

Cited by 74 publications

(108 citation statements)

References 41 publications

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“…1, is expected to change the concentration gradient by saturating the water in between the droplets, which in turn leads to a decrease in the mass loss rate 4 . This change in concentration gradient, caused by the presence of the neighboring droplets, explains the observed increased droplet dissolution time 5 .…”

Section: Introductionmentioning

confidence: 79%

“…1, with the exception of the outermost droplets in the largest pattern. All droplets in the experiments dissolved in the stick-jump mode 3,5,6 , causing the contact angle θ of the droplet to vary between 65 • and 70 • . The time to create the largest pattern (127 droplets) was ≈ 15 minutes, which should be compared to the total dissolution time of > 2.5 hours.…”

Section: Methodsmentioning

confidence: 99%

“…Therefore we must also correct the (dissolution) time based on the initial volume, which in diffusive problems is usually achieved by scaling with the appropriate time scale, namely the diffusive time scale τ d = R 2 0 ρ/(∆cD), where R 0 is the initial droplet radius, and ∆c = c s − c ∞ . Scaling the time in such a way allows to compare purely diffusive droplet dissolution behavior, independent of the initial droplet size or the material 5,15 . Unfortunately, the diffusive time scale τ d cannot be used in the current system as the mass transport is not purely diffusive.…”

Section: Single Dropletmentioning

confidence: 99%

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Collective and convective effects compete in patterns of dissolving surface droplets

Laghezza¹,

Dietrich

Yeomans³

et al. 2016

Soft Matter

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Detlef (2016) Collective and convective effects compete in patterns of dissolving surface droplets. Soft Matter, 12 (26 Northumbria University has developed Northumbria Research Link (NRL) to enable users to access the University's research output. Copyright © and moral rights for items on NRL are retained by the individual author(s) and/or other copyright owners. Single copies of full items can be reproduced, displayed or performed, and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided the authors, title and full bibliographic details are given, as well as a hyperlink and/or URL to the original metadata page. The content must not be changed in any way. Full items must not be sold commercially in any format or medium without formal permission of the copyright holder. The full policy is available online: http://nrl.northumbria.ac.uk/policies.html This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.) This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication.Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available.You can find more information about Accepted Manuscripts in the Information for Authors. The effect of neighboring droplets on the dissolution of a sessile droplet, i.e. collective effects, are investigated both experimentally and numerically. On the experimental side small 20 n approximately mono-disperse surface droplets arranged in an ordered pattern were dissolved and their size evolution is studied optically. The droplet dissolution time was studied for various droplet patterns. On the numerical side, Lattice-Boltzmann simulations were performed. Both simulations and experiments show that the dissolution time of a droplet placed in the center of a pattern can increase with as much as 60% as compared to a single, isolated droplet, due to the shielding effect of the neighboring droplets. However, the experiments also show that neighboring droplets enhance the buoyancy driven convective flow of the bulk, increasing the mass exchange and counteracting collective effects. We show that this enhanced convection can reduce the dissolution time of droplets at the edges of the pattern to values below that of a single, isolated droplet.

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Section: Introductionmentioning

confidence: 79%

Section: Methodsmentioning

confidence: 99%

Section: Single Dropletmentioning

confidence: 99%

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Collective and convective effects compete in patterns of dissolving surface droplets

Laghezza¹,

Dietrich

Yeomans³

et al. 2016

Soft Matter

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“…Since the footprint radius R fp shows steps due to the stick-jump mode dissolution Zhang et al 2015), we define the equivalent radius R ≡ (3V/(2π)) 1/3 to provide a continuously decreasing measure for the droplet size. Figure 6 shows R(t) for 1-pentanol (a) and 1-heptanol (b) droplets.…”

Section: Dissolution Ratementioning

confidence: 99%

“…Figure 1 shows an example of a sessile 1-hexanol droplet in water dissolving in the stick-jump mode Zhang et al 2015): unavoidable chemical and geometrical inhomogeneities in the substrate cause the contact line of the droplet to be pinned during dissolution, until the contact angle θ has decreased to a critical depinning value, which was found to be 62 • ± 2 • . At this point, the contact line depins and the contact angle quickly increases to a value θ = 66 • ± 1 • , resulting in a simultaneous decrease of the footprint radius R fp .…”

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confidence: 98%

Role of natural convection in the dissolution of sessile droplets

Dietrich

Wildeman²,

Visser³

et al. 2016

J. Fluid Mech.

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The dissolution process of small (initial (equivalent) radius R 0 < 1 mm) long-chain alcohol (of various types) sessile droplets in water is studied, disentangling diffusive and convective contributions. The latter can arise for high solubilities of the alcohol, as the density of the alcohol-water mixture is then considerably less than that of pure water, giving rise to buoyancy-driven convection. The convective flow around the droplets is measured, using micro-particle image velocimetry (µPIV) and the schlieren technique. When non-dimensionalizing the system, we find a universal Sh ∼ Ra 1/4 scaling relation for all alcohols (of different solubilities) and all droplets in the convective regime. Here Sh is the Sherwood number (dimensionless mass flux) and Ra is the Rayleigh number (dimensionless density difference between clean and alcohol-saturated water). This scaling implies the scaling relation τ c ∝ R 5/4 0 of the convective dissolution time τ c , which is found to agree with experimental data. We show that in the convective regime the plume Reynolds number (the dimensionless velocity) of the detaching alcohol-saturated plume follows Re p ∼ Sc −1 Ra 5/8 , which is confirmed by the µPIV data. Here, Sc is the Schmidt number. The convective regime exists when Ra > Ra t , where Ra t = 12 is the transition Ra number as extracted from the data. For Ra Ra t and smaller, convective transport is progressively overtaken by diffusion and the above scaling relations break down.

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Sequential Evaporation–Induced Formation of Polymeric Surface Microdents via Ouzo Effect

Wang

Zeng

et al. 2019

Adv Materials Inter

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micro/nanobubbles. [5] Moreover, surface microdents can potentially act as scaffolds for surface lubricants in the fabrication of lubricating surfaces, [6] which exhibit low contact angle hysteresis and can be used in many applications, such as selfcleaning, [7] anti-icing, [8] and enhanced condensation. [9] Several approaches have been developed to fabricate microdents on solid polymer surfaces, such as soft lithography method, [10] nonsolvent sessile droplets action, [11] solvent droplet etching method, [12] and templating methods. [1b,13] In the soft lithography method, [10] microlenses and a positive photoresist substrate are used to get microdent arrays. In the solvent droplet etching method, a single [12a,c] or a group of solvent droplets [12b] on top of micropillars are transferred to polymer films. The corresponding spots on the polymer films will be etched and microdents can then be generated. In order to obtain smaller microdents, smaller size of solvent droplets can be generated through solvent exchange method. [14] In the templating methods, colloidal particles [1b,13a,e,15] or water droplets [13b-d] (breath figure method) are taken as templates. The templates are first placed on a thin film of solvent with dissolved polymer. After the solvent evaporates, microdents are generated on the spots where the templates locate. Compared with the lithography and solvent droplet etching methods, templating methods are easy to be conducted and are more suitable to fabricate microdents in batches.Recently, "Ouzo effect" was applied to fabricate micro/nanostructures, such as micro/nanodroplets, [16] micro/nanoparticles, [17] and micro/nanolenses. [14b,18] "Ouzo effect" is referred to the nucleation of tiny oil droplets after water is added into a Greek drink of Ouzo. [19] Since the solubility of oil in ethanol-water solution decreases with increase in the water concentration, the oil is oversaturated, spontaneously forming microdroplets after more water is added in the oil-ethanol-water ternary solutions. Instead of adding water into ethanol-oil mixture, evaporation of ethanol in an Ouzo drop can also trigger Ouzo effect. [20] The Ouzo effect provides an efficient approach to produce microdroplets that in turn serve as templates for the formation of micro/nanostructures. [16][17][18] Compared with the existed methods, micro/nanostructure fabrication via Ouzo effect can be conducted without any special setups and complex operations.Here we propose a new templating method to fabricate surface microdents via "Ouzo effect" in a ternary solution. By designing the solution of polystyrene (PS) in the ternary solvents with different volatilities, water droplets can form

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Mixed mode of dissolving immersed nanodroplets at a solid–water interface

Cited by 74 publications

References 41 publications

Collective and convective effects compete in patterns of dissolving surface droplets

Collective and convective effects compete in patterns of dissolving surface droplets

Role of natural convection in the dissolution of sessile droplets

Sequential Evaporation–Induced Formation of Polymeric Surface Microdents via Ouzo Effect

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