Direct Three‐Dimensional Imaging of the Buried Interfaces between Water and Superhydrophobic Surfaces

Luo, Cheng; Zheng, Hua De; Wang, Lei; Fang, Haiping; Hu, Jun; Chen, Fan; Cao, Yong; Wang, Jian

doi:10.1002/anie.201002470

Cited by 71 publications

(51 citation statements)

References 33 publications

(12 reference statements)

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“…The dynamic process of wetting transition from the CB to the W state has been captured by various techniques, such as light reflection, 16,18,[28][29][30] optical diffraction, 31,32 X-ray 33 and confocal microscopy. 17,[34][35][36][37][38] Understanding this phenomenon is critical for the regulation and improvement of CB-based superhydrophobicity and conducive to the design of underwater structured surfaces with enhanced lifetime. Previous analyses on the CB-W transition focused on the energy barriers between the states from an energy point of view, [39][40][41][42][43][44] and the critical pressure at which the liquid-gas interfaces depin from the top edge of the microstructures using a force-balance analysis.…”

Section: Introductionmentioning

confidence: 99%

Symmetric and Asymmetric Meniscus Collapse in Wetting Transition on Submerged Structured Surfaces

Xue²,

Líu³

et al. 2015

Langmuir

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The wetting transition from the Cassie-Baxter to the Wenzel state is a phenomenon critically pertinent to the functionality of microstructured superhydrophobic surfaces. This work focuses on the last stage of the transition, when the liquid-gas interface touches the bottom of the microstructure, which is also known as the "collapse" phenomenon. The process was examined in situ on a submerged surface patterned with cylindrical micropores using confocal microscopy. Both symmetric and asymmetric collapses were observed. The latter significantly shortens the progression of the metastable state prior to the collapse when compared with the former and hence may affect the lifespan of superhydrophobicity. Further experiments identified that asymmetric collapse were induced by impurities due to prior use of the structure. The problem is thus of broad relevance, since endurance through cycles is a practical requirement for these functional surfaces. Finally, the use of hierarchical structures is proposed as a remedy. The embedded self-cleaning mechanism serves to effectively remove the impurities, so as to avoid the triggering mechanism for asymmetric collapses.

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Section: Introductionmentioning

confidence: 99%

Symmetric and Asymmetric Meniscus Collapse in Wetting Transition on Submerged Structured Surfaces

Xue²,

Líu³

et al. 2015

Langmuir

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“…Although they did not measure nanoscale contact angles directly, the drops nevertheless exhibited advancing and receding fronts as they moved along a surface. There have been only a handful of experimental investigations of micro-capillary bridges, and all high-resolution imaging has been restricted to static drops24383940414243. Though some have examined the dynamic behaviour, the limited resolution of the three-dimensional details leaves the deformation processes unclear23334445.…”

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confidence: 99%

Self-similarity of contact line depinning from textured surfaces

2013

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The mobility of drops on surfaces is important in many biological and industrial processes, but the phenomena governing their adhesion, which is dictated by the morphology of the three-phase contact line, remain unclear. Here we describe a technique for measuring the dynamic behaviour of the three-phase contact line at micron length scales using environmental scanning electron microscopy. We examine a superhydrophobic surface on which a drop’s adhesion is governed by capillary bridges at the receding contact line. We measure the microscale receding contact angle of each bridge and show that the Gibbs criterion is satisfied at the microscale. We reveal a hitherto unknown self-similar depinning mechanism that shows how some hierarchical textures such as lotus leaves lead to reduced pinning, and counter-intuitively, how some lead to increased pinning. We develop a model to predict adhesion force and experimentally verify the model’s broad applicability on both synthetic and natural textured surfaces.

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“…After subsequent spin coating cycles, the SCA increases to values above 150 , while the SA decreases dramatically to values in the range of 10-20 . Most likely, droplets are no longer in the complete Wenzel state, but more in a mixed state [12,[32][33][34] with partial impregnation of the structured surfaces. In agreement with the still relatively large SA values, analysis of the results reveals that on these single length scale superstructures, the droplets move slowly.…”

Section: A)mentioning

confidence: 99%

Hydrophobic surfaces with tunable dynamic wetting properties via colloidal assembly of silica microspheres and gold nanoparticles

Raza

Zandvliet

Poelsema

et al. 2014

J Sol-Gel Sci Technol

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Hierarchically structured surfaces have been fabricated using a simple colloidal bottom-up approach. The substrates exhibit a wide range of wettability properties, expressed by water contact angles ranging from 110 to 166 . The liquid-solid adhesive characteristics vary from very sticky to non-sticky, exhibited by very large and negligible sliding angles, respectively. Silica spheres with diameters in the range 130-850 nm comprise the larger length scale entities in the hierarchical superstructures, while gold nanoparticles with diameters 13-45 nm are included as the smaller length scale features. Surfaces are derivatized with suitable chemical agents to render them (super)hydrophobic. Dynamic wetting properties in terms of contact angle hysteresis and sliding angles are discussed in relation to the surface morphology.

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Direct Three‐Dimensional Imaging of the Buried Interfaces between Water and Superhydrophobic Surfaces

Cited by 71 publications

References 33 publications

Symmetric and Asymmetric Meniscus Collapse in Wetting Transition on Submerged Structured Surfaces

Symmetric and Asymmetric Meniscus Collapse in Wetting Transition on Submerged Structured Surfaces

Self-similarity of contact line depinning from textured surfaces

Hydrophobic surfaces with tunable dynamic wetting properties via colloidal assembly of silica microspheres and gold nanoparticles

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