How the change of contact angle occurs for an evaporating droplet: effect of impurity and attached water films

Park, Jun Kwon; Ryu, Jeongeun; Koo, Bonchull C.; Lee, Sang‐Hyun; Kang, Kwan Hyoung

doi:10.1039/c2sm26559a

Cited by 42 publications

(39 citation statements)

References 57 publications

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“…The shape of the droplet is assumed to maintain a hemispherical form, which is a reasonable assumption for the case of droplets placed on a hydrophobic surface. 1,36 This assumption is essential to derive analytical expressions for the scaling relation, and it greatly simplifies the numerical procedures.…”

Section: Formulation Of Governing Equationsmentioning

confidence: 99%

Evaporation-induced saline Rayleigh convection inside a colloidal droplet

et al. 2013

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Inside evaporating two-component sessile droplets, a family of the Rayleigh convection exists, driven by salinity gradient formed by evaporation of solvent and solute. In this work, the characteristic of the flow inside an axisymmetric droplet is investigated. A stretched coordinate system is employed to account for the effect of boundary movement. A scaling analysis shows that the flow velocity is proportional to the (salinity) Rayleigh number (Ras) at the small-Rayleigh-number limit. A numerical analysis for a hemispherical droplet exhibits the flow velocity is proportional to the non-dimensional number \documentclass[12pt]{minimal}\begin{document}$Ra_s^{1/2}$\end{document}Ras1/2, at high Rayleigh numbers. A self-similar condition is established for the concentration field irrespective of the Rayleigh numbers after a moderate time, and the flow field is invariant with time at this stage. The scaling relation for the high Rayleigh numbers is verified experimentally by using aqueous NaCl droplets.

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Section: Formulation Of Governing Equationsmentioning

confidence: 99%

Evaporation-induced saline Rayleigh convection inside a colloidal droplet

et al. 2013

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“…(9)(10)(11)(12) Additionally, we can also suspect that the SAM substrate in air may result in a random adsorption of Airborne Molecular Contamination (AMC). (27) During the experiment, the substrate is exposed to air.…”

Section: Resultsmentioning

confidence: 99%

“…(9)(10)(11)(12) This non-uniformly receding contact line pattern is due to various reasons, e.g. heterogeneities of the surface, impurities inside the droplet, and so on.…”

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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“…The contact angle of the droplet on chemically patterned surface is determined by the solid-liquid interaction on the three-phase contact line. Li et al [15] analyzes the local force balance in the diffuse interfaces and proposed the following equation cos = cos + cos (22) where is the characteristic contact angle of the droplets on chemically stripe-patterned surfaces, and are the length ratios of the contact line occupied by components A and B.…”

Section: Spreading Of Droplets On the Stripe-patterned Surface Withoumentioning

confidence: 99%

“…In recent years, tremendous research efforts have been made in investigating the pinning-depinning mechanism [13][14][15][16][17][18] on patterned surfaces, such as structurally rough surfaces [19][20][21][22][23] and chemically heterogeneous surfaces [24][25][26][27][28][29]. The pinning and depinning forces [20,30] and the intrinsic energy barrier [23,31]were used to explain the pinning-depinning mechanism.…”

Section: Introductionmentioning

confidence: 99%

3D Lattice Boltzmann Simulation of Droplet Evaporation on Patterned Surfaces: Study of Pinning-Depinning Mechanism

Dong

Wang

Zhang

et al. 2019

Preprint

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The liquid-vapor phase change lattice Boltzmann method is used to investigate the pinning-depinning mechanism of the contact line during droplet evaporation on the stripe-patterned surfaces in 3D space. Considering the curvature of the contact line and the direction of the unbalanced Young’s force, the local force balance theory near the stripe boundary is proposed to explain the steady state of the droplets on the stripe-patterned surfaces. An equation is proposed to evaluate the characteristic contact angle of the stabilized droplets. During the evaporation of the droplet, the stick-slip-jump behavior and the CCR-Mixed-CCA mode can be well captured by the lattice Boltzmann simulation. When the contact line is pinned to the stripe boundary, the contact line in the direction perpendicular to the stripes is slowly moving while the curvature of the contact line is gradually increasing. The gradually increasing curvature of the contact line accelerates the movement of the contact line, and the final contact line is detached from the stripe boundary. The research results provide theoretical support and guidance for the design, improvement and application of patterned surfaces in the field of micro-fluidic and evaporation heat transfer.

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How the change of contact angle occurs for an evaporating droplet: effect of impurity and attached water films

Cited by 42 publications

References 57 publications

Evaporation-induced saline Rayleigh convection inside a colloidal droplet

Evaporation-induced saline Rayleigh convection inside a colloidal droplet

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

3D Lattice Boltzmann Simulation of Droplet Evaporation on Patterned Surfaces: Study of Pinning-Depinning Mechanism

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