Analytical solution for Stokes flow inside an evaporating sessile drop: Spherical and cylindrical cap shapes

Masoud, Hassan; Felske, James D.

doi:10.1063/1.3112002

Cited by 58 publications

(61 citation statements)

References 31 publications

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“…A close inspection of previous studies on evaporationinduced flow inside sessile drops [47,49,50,[54][55][56] reveals that Stokes and potential (inviscid) flows are simi- ) and (c) Radial distribution of height-averaged concentration of particles at t/t f = 0.12, 0.51, 0.9. Here,C denotes the total (bulk and surface) concentration of solutes averaged over the height of the drop z b at each radial position, and z bC is normalized by its corresponding value at r/R = 0 and t/t f = 0.12.…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, the intersection with the liquid-gas interface is expected as a consequence of the velocity of the fluid always carrying the particles towards the free surface (see, e.g., Refs. [49,50]). To develop a proper mathematical model for the deposition, it is then crucial to know what fraction of particles intersect the interface during the life time of the drop.…”

Section: Description Of Modelmentioning

confidence: 99%

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Alternative mechanism for coffee-ring deposition based on active role of free surface

et al. 2016

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When a colloidal sessile droplet dries on a substrate, the particles suspended in it usually deposit in a ring-like pattern. This phenomenon is commonly referred to as the "coffee-ring" effect. One paradigm for why this occurs is as a consequence of the solutes being transported towards the pinned contact line by the flow inside the drop, which is induced by surface evaporation. From this perspective, the role of the liquid-gas interface in shaping the deposition pattern is somewhat minimized. Here, we propose an alternative mechanism for the coffee-ring deposition. It is based on the bulk flow within the drop transporting particles to the interface where they are captured by the receding free surface and subsequently transported along the interface until they are deposited near the contact line. That the interface captures the solutes as the evaporation proceeds is supported by a Lagrangian tracing of particles advected by the flow field within the droplet. We model the interfacial adsorption and transport of particles as a one-dimensional advection-generation process in toroidal coordinates and show that the theory reproduces ring-shaped depositions. Using this model, deposition patterns on both hydrophilic and hydrophobic surfaces are examined in which the evaporation is modeled as being either diffusive or uniform over the surface.

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Section: Resultsmentioning

confidence: 99%

Section: Description Of Modelmentioning

confidence: 99%

Alternative mechanism for coffee-ring deposition based on active role of free surface

et al. 2016

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“…Normally, in the evaporating droplet problem where the contact line is pinned everywhere, a zero shear stress boundary condition is applied at the liquid interface. (7,32) However, in this study case, the tangential stress along near the liquid interface is no longer free because the shrinking rate of the droplet interface is not uniform everywhere while the contact line non-uniformly recedes.…”

Section: Resultsmentioning

confidence: 99%

“…flowing from the moving contact line to the center of the droplet. (7,8) In sum, the internal flow pattern is related to the contact line receding pattern.…”

Section: Introductionmentioning

confidence: 99%

Tomographic PIV measurement of internal complex flow of an evaporating droplet with non-uniformly receding contact lines

Kim¹,

Belmiloud²,

Mertens³

2016

Journal of the Korean Society of Visualization

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We investigate an internal flow pattern of an evaporating droplet where the contact line non-uniformly recedes. By using tomographic Particle Image Velocimetry, we observe a three-dimensional azimuthal vortex pair that is maintained until the droplet is completely dried. The non-uniformly receding contact line motion breaks the flow symmetry. Finally, a simplified scaling model presents that the mechanical stress along the contact line is proportional to the vorticity magnitude, which is validated by the experimental results.

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“…Despite its complexity, to the first approximation, this mechanism can be regarded (and analyzed) as the superposition of simpler effects. These effects are: (i) the displacement of particles inside an evaporating drop driven by convection and diffusion [32,33]; and (ii) the translocation or capture of a molecule through a nanopore [30,[34][35][36].…”

Section: Figurementioning

confidence: 99%

The Five Ws (and one H) of Super-Hydrophobic Surfaces in Medicine

et al. 2014

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Super-hydrophobic surfaces (SHSs) are bio-inspired, artificial microfabricated interfaces, in which a pattern of cylindrical micropillars is modified to incorporate details at the nanoscale. For those systems, the integration of different scales translates into superior properties, including the ability of manipulating biological solutions. The five Ws, five Ws and one H or the six Ws (6W), are questions, whose answers are considered basic in information-gathering. They constitute a formula for getting the complete story on a subject. According to the principle of the six Ws, a report can only be considered complete if it answers these questions starting with an interrogative word: who, why, what, where, when, how. Each question should have a factual answer. In what follows, SHSs and some of the most promising applications thereof are reviewed following the scheme of the 6W. We will show how these surfaces can be integrated into bio-photonic devices for the identification and detection of a single molecule. We will describe how SHSs and nanoporous silicon matrices can be combined to yield devices with the capability of harvesting small molecules, where the cut-off size can be adequately controlled. We will describe how this concept is utilized for obtaining a direct TEM image of a DNA molecule. OPEN ACCESSMicromachines 2014, 5 240

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Analytical solution for Stokes flow inside an evaporating sessile drop: Spherical and cylindrical cap shapes

Cited by 58 publications

References 31 publications

Alternative mechanism for coffee-ring deposition based on active role of free surface

Alternative mechanism for coffee-ring deposition based on active role of free surface

Tomographic PIV measurement of internal complex flow of an evaporating droplet with non-uniformly receding contact lines

The Five Ws (and one H) of Super-Hydrophobic Surfaces in Medicine

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