Liquid spreading on superhydrophilic micropillar arrays

Kim, Seong‐Jin; Moon, Myoung‐Woon; Lee, Kwang-Ryeol; Lee, Dae-Young; Chang, Young Soo; Kim, Ho-Young

doi:10.1017/jfm.2011.210

Cited by 83 publications

(86 citation statements)

References 19 publications

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“…What is the physical mechanism of this transition? In figure 7(a,b) we can find that although R b expanded more slowly than R f , they scaled similarly, which is also validated by the experiments (Kim et al 2011). According to the MD simulations, we would assume αR b ∼ R f ∼ t n in the next section.…”

Section: Molecular Dynamics Simulationssupporting

confidence: 72%

“…In the spreading process, αR b ∼ R f ∼ R is validated by Kim et al (2011) and our MD simulations, where α (α 1) is independent of time.…”

Section: Scaling Analysis Using Molecular Kinetic Theorysupporting

confidence: 62%

“…a thin liquid film wetting the solid surface, while a droplet is preferred in practical applications. Kim et al proposed a scaling law of R f ∼ t 1/4 in the early stage of a droplet spreading on the pillar array using the hydrodynamic model (Kim et al 2011), but the results could not degenerate to a droplet on a smooth surface when ro approaches 1. There is a lack of a systematic and multiscale study of the dynamic wetting of a droplet on the rough surface.…”

Section: Introductionmentioning

confidence: 99%

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Multiscale dynamic wetting of a droplet on a lyophilic pillar-arrayed surface

2013

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Dynamic wetting of a droplet on lyophilic pillars was explored using a multiscale combination method of experiments and molecular dynamics simulations. The excess lyophilic area not only provided excess driving force, but also pinned the liquid around the pillars, which kept the moving contact line in a dynamic balance state every period of the pillars. The flow pattern and the flow field of the droplet on the pillar-arrayed surface, influenced by the concerted effect of the liquid-solid interactions and the surface roughness, were revealed from the continuum to the atomic level. Then, the scaling analysis was carried out employing molecular kinetic theory. Controlled by the droplet size, the density of roughness and the pillar height, two extreme regimes were distinguished, i.e. R ∼ t 1/3 for the rough surface and R ∼ t 1/7 for the smooth surface. The scaling laws were validated by both the experiments and the simulations. Our results may help in understanding the dynamic wetting of a droplet on a pillar-arrayed lyophilic substrate and assisting the future design of pillar-arrayed lyophilic surfaces in practical applications.

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Section: Molecular Dynamics Simulationssupporting

confidence: 72%

“…In the spreading process, αR b ∼ R f ∼ R is validated by Kim et al (2011) and our MD simulations, where α (α 1) is independent of time.…”

Section: Scaling Analysis Using Molecular Kinetic Theorysupporting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

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Multiscale dynamic wetting of a droplet on a lyophilic pillar-arrayed surface

2013

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“…Courbin et al [25] reported the dynamics of shape evolution, while the mechanism in the process of evolution is still demanded. Kim and coworkers [26] quantified the dynamics of polygonal spreading and proposed the scaling laws for spreading rates of the bulk and the fringe separately, when the shape evolution of the bilayer structure has not been investigated yet.…”

Section: Introductionmentioning

confidence: 99%

Dynamic polygonal spreading of a droplet on a lyophilic pillar-arrayed surface

Chen

Yuan

Huang

et al. 2016

Journal of Adhesion Science and Technology

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We experimentally investigated the dynamic polygonal spreading of droplets on lyophilic pillar-arrayed substrates. When deposited on lyophilic rough surfaces, droplets adopt dynamic evolutions of projected shapes from initial circles to final bilayer polygons. These dynamic processes are distinguished in two regimes on the varied substrates. The bilayer structure of a droplet, induced by micropillars on the surface, was explained by the interaction between the fringe (liquid in the space among the micropillars) and the bulk (upper liquid). The evolution of polygonal shapes, following the symmetry of the pillar-arrayed surface, was analysed by the competition effects of excess driving energy and resistance which were induced by micropillars with increasing solid surface area fraction. Though the anisotropic droplets spread in different regimes, they obey the same scaling law S ~ t 2/3 (S being the wetted area and t being the spreading time), which is derived from the molecular kinetic theory. These results may expand our knowledge of the liquid dynamics on patterned surfaces and assist surface design in practical applications.

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“…Remarkably, it has been shown that the symmetry of the pillar array typically controls the shape of the wetting front of the drop, which can be faceted as a square (or an octagon) when the drop is deposited on a square array of pillars, or as a hexagon on a hexagonal array [2,5,6]. Following these works, an intense more recent effort has been dedicated to analyzing how the geometrical characteristics of the texture influence the advancing front dynamics [7][8][9][10][11][12][13]. Interestingly, some peculiar "microscopic" mechanisms of contact line motion were evidenced in some of these works, such as the so-called zipping mechanism which consists in the wetting of an individual pillar of the next row by the liquid front, followed by lateral progression along this row [6,11].…”

mentioning

confidence: 99%

Evaporation dynamics of completely wetting drops on geometrically textured surfaces

Mekhitarian¹,

Sobac²,

Dehaeck³

et al. 2017

EPL

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-This study deals with the evaporation dynamics of completely wetting and highly volatile drops deposited on geometrically textured but chemically homogeneous surfaces. The texturation consists in a cylindrical pillars array with a square pitch. The triple line dynamics and the drop shape are characterized by an interferometric method. A parametric study is realized by varying the radius and the height of the pillars (at fixed interpillar distance), allowing to distinguish three types of dynamics: i) an evaporation-dominated regime with a receding triple line; ii) a spreading-dominated regime with an initially advancing triple line; iii) a cross-over region with strong pinning effects. The overall picture is in qualitative agreement with a mathematical model showing that the selected regime mostly depends on the value of a dimensionless parameter comparing the time scales for evaporation and spreading into the substrate texture. Introduction. -Wetting and evaporation of liquid drops on solid surfaces are of prime importance for a wide range of applications, from biomedicine and operation of DNA chips to painting and design of self-cleaning and antifouling surfaces. On the other hand, the recent development of small-scale fabrication techniques enables producing surfaces with well-defined chemical and/or geometrical textures, in the micron-range or even at the nanoscale. This offers a large range of new research possibilities, aiming in particular to improve the fundamental knowledge of wetting and evaporation/condensation of liquids on textured surfaces. In turn, a very promising outcome of such improved basic understanding could be the targeted manufacturing of novel hierarchical structures with potential applications in photovoltaics, substrates for engineered cell growth or other smart materials [1].In this work, we focus on surfaces geometrically textured by an array of cylindrical pillars with controlled dimensions (typically tens of microns). Previous studies have shown how such large-scale "roughness" influences the wetting of a drop deposited on the surface [2-4] by enhancing its wettability or non-wettability (i.e., by affecting its apparent contact angle and wetting surface). These works in particular highlighted that, in partial wetting situations, a part of the liquid can invade the surface

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Liquid spreading on superhydrophilic micropillar arrays

Cited by 83 publications

References 19 publications

Multiscale dynamic wetting of a droplet on a lyophilic pillar-arrayed surface

Multiscale dynamic wetting of a droplet on a lyophilic pillar-arrayed surface

Dynamic polygonal spreading of a droplet on a lyophilic pillar-arrayed surface

Evaporation dynamics of completely wetting drops on geometrically textured surfaces

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