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

Chen, Enhui; Yuan, Quanzi; Huang, Xianfu; Zhao, Ya‐Pu

doi:10.1080/01694243.2016.1179824

Cited by 10 publications

(7 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The droplets in Raj et al 22 demonstrated finite contact angles in the nonpropagating regime and allowed superior control over fluidic manipulation. Similar shapes in the thin-film regime or directional spreading have been previously demonstrated on microdecorated surfaces, 23 lyophilic pillararrayed surfaces, 24,25 and chemically patterned micropillar surfaces 26,27 as well. Similarly, droplets with polygonal contact line can also be obtained by varying the concentration of a binarymixture on a microdecorated substrate.…”

Section: ■ Introductionsupporting

confidence: 81%

Droplets on Microdecorated Surfaces: Evolution of the Polygonal Contact Line

Kumar

Raj

2017

Langmuir

View full text Add to dashboard Cite

Interaction of liquids with surfaces is ubiquitous in our physical environment as well as many engineering applications. Recent advances on this topic have not only provided us with valuable insight into nature's design, but also enabled improved fluidic manipulation for liquid-based printing applications such as biomicroarrays for protein and DNA sequencing, multicolor polymer-based LED displays, inkjet printing, and solder droplet printing, among others. For example, droplet contact lines, which are typically circular on a smooth and homogeneous surface, when deposited on a microdecorated surface may take various common polygonal shapes such as squares, rectangles, hexagons, octagons and dodecagons. These polygonal contact line shapes are highly stable due to the local energy barriers associated with the anisotropy in depinning contact angles. In addition to the knowledge of the eventual contact line shapes, liquid-based printing applications would require accurate prediction of temporal evolution of contact line on these surfaces. In this work, we model and validate the evolution of droplets on microdecorated surfaces with microgoniometry experiments reported in the literature. We show that various metastable contact line shapes are formed in-between the well-known stable polygonal contact line shapes usually observed in experiments. We elucidate that the movement of the contact line between adjacent micropillars can primarily be categorized as primary zipping and transition zipping. Primary zipping occurs when the contact line moves radially outward to the next row of pillars, often resulting in the formation of a metastable contact line shape. Conversely, metastable droplet attains stable polygonal contact line shape via transition zipping wherein the contact line advances sideways. We believe that the current simulation approach can be effectively utilized for designing optimized textured surfaces for applications where control over liquid supply via surface design is required.

show abstract

Section: ■ Introductionsupporting

confidence: 81%

Droplets on Microdecorated Surfaces: Evolution of the Polygonal Contact Line

Kumar

Raj

2017

Langmuir

View full text Add to dashboard Cite

show abstract

“…Similar to the way it influences spontaneous spreading (see, for example, the elegant studies in ref 46,47), it should also influence spontaneous triple line retraction, namely work of adhesion measurements. As in other wetting properties, it is expected to depend on whether the roughness results in a Wenzel or in a Cassie regime.…”

Section: ■ Results and Discussionmentioning

confidence: 84%

“…Surface roughness plays a significant role in wetting phenomena. Similar to the way it influences spontaneous spreading (see, for example, the elegant studies in ref , ), it should also influence spontaneous triple line retraction, namely work of adhesion measurements. As in other wetting properties, it is expected to depend on whether the roughness results in a Wenzel or in a Cassie regime. , It is expected that a Wenzel regime will result in a higher work of adhesion, while Cassie regime will result in a lower work of adhesion.…”

Section: Resultsmentioning

confidence: 86%

Solid–Liquid Work of Adhesion

et al. 2017

View full text Add to dashboard Cite

We establish a tool for direct measurements of the work needed to separate a liquid from a solid. This method mimics a pendant drop that is subjected to a gravitational force that is slowly increasing until the solid-liquid contact area starts to shrink spontaneously. The work of separation is then calculated in analogy to Tate's law. The values obtained for the work of separation are independent of drop size and are in agreement with Dupré's theory, showing that they are equal to the work of adhesion.

show abstract

“…The higher aspect ratio of the droplets on ME is also consistent with the formation of filaments droplet on the grooves. 30 Although the roughness measured from AFM images was only 3.3 nm in RMS, the boundary of the oil nanodroplets in the solution of pH 3.0 was clearly pinned along the layers of MoS 2 edge. It is remarkable that the layered nanostructure of MoS 2 edge surface is already sufficient to lead to pronounced effects on the formation and morphology of nanodroplets.…”

Section: ■ Experimental Sectionmentioning

confidence: 95%

Microwetting of pH-Sensitive Surface and Anisotropic MoS₂ Surfaces Revealed by Femtoliter Sessile Droplets

Peng

et al. 2016

Langmuir

View full text Add to dashboard Cite

Understanding the microwettability of anisotropic molybdenum disulfide crystal is critically important in separation and processing of this material in liquid. In this work, static microwetting properties of MoS face (MF) and MoS edge (ME) surfaces in water are revealed by the morphology of femtoliter interfacial droplets. The oil droplets with different size distribution were produced from heterogeneous nucleation and growth of nanodroplets during the solvent exchange under controlled flow and solution conditions, and were polymerized for droplet morphology characterization to reveal the relative wettability of the droplets on surfaces. We first demonstrate that the shape of the nanodroplets is responsive to the surface charges on a model pH sensitive substrate of gold coated with a self-assembled monolayer of two types of thiol. The experimental results on MoS substrates indicate that (1) oil contact angle of the droplets on ME surface is much larger than that on MF surface at pH 3.0, suggesting that the ME surface is more hydrophilic than MF; (2) the droplets are pinned by the layered nanostructure on MoS edge. The fundamental understanding of microwettability elucidated in this study may allow for an improved control of the interaction between anisotropic MoS surfaces and the surrounding liquid environment, which is critically important for many industrial applications such as flotation and catalysis systems.

show abstract

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

Cited by 10 publications

References 35 publications

Droplets on Microdecorated Surfaces: Evolution of the Polygonal Contact Line

Droplets on Microdecorated Surfaces: Evolution of the Polygonal Contact Line

Solid–Liquid Work of Adhesion

Microwetting of pH-Sensitive Surface and Anisotropic MoS₂ Surfaces Revealed by Femtoliter Sessile Droplets

Contact Info

Product

Resources

About

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

Cited by 10 publications

References 35 publications

Droplets on Microdecorated Surfaces: Evolution of the Polygonal Contact Line

Droplets on Microdecorated Surfaces: Evolution of the Polygonal Contact Line

Solid–Liquid Work of Adhesion

Microwetting of pH-Sensitive Surface and Anisotropic MoS2 Surfaces Revealed by Femtoliter Sessile Droplets

Contact Info

Product

Resources

About

Microwetting of pH-Sensitive Surface and Anisotropic MoS₂ Surfaces Revealed by Femtoliter Sessile Droplets