Bubbles nucleating on superhydrophobic micropillar arrays under flow

Pinchasik, Bat‐El; Schönfeld, Friedhelm; Kappl, Michael; Butt, Hans‐Jürgen

doi:10.1039/c9sm01224a

Cited by 9 publications

(8 citation statements)

References 48 publications

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“…4). Further, it has been reported that flow increases the rate of growth of nanobubbles on superhydrophobic surfaces 53,54 . On LIS, higher flow rates increase the portions of exposed areas of the Teflon substrate to the water and, therefore, we expect that higher flow also increases nucleation site density.…”

Section: Resultsmentioning

confidence: 98%

Nanobubbles explain the large slip observed on lubricant-infused surfaces

2022

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Lubricant-infused surfaces hold promise to reduce the huge frictional drag that slows down the flow of fluids at microscales. We show that infused Teflon wrinkled surfaces induce an effective slip length 50 times larger than expected based on the presence of the lubricant alone. This effect is particularly striking as it occurs even when the infused lubricant’s viscosity is several times higher than that of the flowing liquid. Crucially, the slip length increases with increasing air content in the water but is much higher than expected even in degassed and plain Milli-Q water. Imaging directly the immersed interface using a mapping technique based on atomic force microscopy meniscus force measurements reveals that the mechanism responsible for this huge slip is the nucleation of surface nanobubbles. Using a numerical model and the height and distribution of these surface nanobubbles, we can quantitatively explain the large fluid slip observed in these surfaces.

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Section: Resultsmentioning

confidence: 98%

Nanobubbles explain the large slip observed on lubricant-infused surfaces

2022

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“…For the surface of square cylinder microstructure, the total shear stress and pressure drop energy will be greatly affected by staggered and aligned arrangement, but not for triangular microstructure. Bat et al [76] studied the effect of cylinder shape on gas nucleation in saturated aqueous solution (Figure 3a,b). It was found that the shape and arrangement of hydrophobic microcolumns have an effect on bubble nucleation, and the flow direction also affects bubble nucleation.…”

Section: Layout and Shape Of The Microstructuresmentioning

confidence: 99%

Section: Layout and Shape Of The Microstructuresmentioning

confidence: 99%

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Recent Developments of Superhydrophobic Surfaces (SHS) for Underwater Drag Reduction Opportunities and Challenges

Feng

Sun

Tian

2021

Adv Materials Inter

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Superhydrophobic surfaces (SHS) for underwater drag reduction draw more and more attention owing to its promising and wide applications such as underwater vehicles, pipeline oil transportation, and aquaculture. However, the drag reduction properties are inextricably linked to the stability of air layer on SHS. This review highlights recent advances regarding SHS for underwater drag reduction in the past three years. First, the fundamental theories are briefly described. Next, the crucial influencing factors, which include dimension and arrangement of particles, layout, and shape of the microstructures, Reynolds number, and attack angle on underwater drag reducing performance of SHS are thoroughly listed. Furthermore, the superior or inferior of these manufacturing techniques is also individually illustrated. After that, the solutions of enhancing stability of the air layer are explicitly classified. Then, the practical applications and its potential value in ships and underwater vehicles, microchannels, as well as fabrics are briefly discussed. Finally, the remaining challenges and promising breakthroughs in the field of SHS for underwater drag reduction are clarified in depth.

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“…Moreover, fine‐tuning of buoyant forces and even neutral buoyancy could be achieved by controlling bubble nucleation in submerged devices. [ 63 ] This approach includes electrowetting, [ 64 ] electrocatalysis, [ 65 ] acoustic waves, [ 26 ] heating (plasmonic local heating or overall heating), [ 66 ] nucleation from a supersaturated solution [ 67 ] and others. In the context of miniature robotics, this becomes even more challenging as fuel may not be possible to integrate into a small scale system and will deplete over time.…”

Section: Diving Swimming and Buoyancy Regulationmentioning

confidence: 99%

How Can Interfacial Phenomena in Nature Inspire Smaller Robots

Das

Pinchasik

2020

Adv Materials Inter

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In nature, surfaces are evolutionarily designed to allow adaptation of species to their environments. Insects make extensive use of interfacial phenomena because of their small size and thus, large surface‐area‐to‐volume ratio. This enables them to walk on different terrains, dive, swim, and adhere to surfaces in air and underwater. Moreover, they toggle between different interfaces, move in confined spaces, and overcome a wide range of obstacles. This progress report summarizes emerging directions in the field of bioinspired robotics with an emphasis on micro and nanoscale dynamic interactions. It is envisioned that interfacial phenomena will allow to miniaturize robots and increase the complexity of their operation. The key to success is the combination of functional surfaces, structural design and multiple modes of locomotion. For this to be realized, however, new paradigms are needed in terms of materials, fabrication, energy consumption, and actuation. This report discusses the development of small robots inspired by water striders, the bell spider, the leaf and ladybird beetles, backswimmers and cockroaches, among many others. It also discusses small soft robots inspired by roundworms, larvae, and parasites. From a broader perspective, fabrication of many small robots will enable to study collective effects and self‐assembly, group behavior and swarming.

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Bubbles nucleating on superhydrophobic micropillar arrays under flow

Abstract: When a supersaturated aqueous solution flows over a microstructured, hydrophobic surface, bubbles tend to nucleate. Here, we control heterogeneous nucleation of gas bubbles from supersaturated CO2 solution.

Cited by 9 publications

References 48 publications

Nanobubbles explain the large slip observed on lubricant-infused surfaces

Nanobubbles explain the large slip observed on lubricant-infused surfaces

Recent Developments of Superhydrophobic Surfaces (SHS) for Underwater Drag Reduction Opportunities and Challenges

How Can Interfacial Phenomena in Nature Inspire Smaller Robots

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