Cassie-State Stability of Metallic Superhydrophobic Surfaces with Various Micro/Nanostructures Produced by a Femtosecond Laser

Abstract Highly stretchable and robust superhydrophobic surfaces have attracted tremendous interest due to their broad application prospects. In this work, silicone elastomers were chosen to fabricate superhydrophobic surfaces with femtosecond laser texturing method, and high stretchability and tunable adhesion of the superhydrophobic surfaces were demonstrated successfully. To our best knowledge, it is the first time flexible superhydrophobic surfaces with a bearable strain up to 400% are fabricated by simple laser ablation. The test also shows that the strain brings no decline of water repellency but an enhancement to the superhydrophobic surfaces. In addition, a stretching-induced transition from “petal” state to “lotus” state of the laser-textured surface was also demonstrated by non-loss transportation of liquid droplets. Our results manifest that femtosecond laser ablating silicone elastomer could be a promising way for fabricating superhydrophobic surface with distinct merits of high stretchability, tunable adhesion, robustness, and non-fluorination, which is potentially useful for microfluidics, biomedicine, and liquid repellent skin.

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Substrate-Independent, Fast, and Reversible Switching between Underwater Superaerophobicity and Aerophilicity on the Femtosecond Laser-Induced Superhydrophobic Surfaces for Selectively Repelling or Capturing Bubbles in Water

ACS Applied Materials & Interfaces ◽

10.1021/acsami.8b21465 ◽

2019 ◽

Vol 11 (8) ◽

pp. 8667-8675 ◽

Cited By ~ 25

Author(s):

Jiale Yong ◽

Subhash C. Singh ◽

Zhibing Zhan ◽

Feng Chen ◽

Chunlei Guo

Keyword(s):

Femtosecond Laser ◽

Superhydrophobic Surfaces ◽

Substrate Independent

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SURFACE EVOLVER SIMULATIONS OF DROPS ON MICROPOSTS

International Journal of Modern Physics C ◽

10.1142/s012918311240013x ◽

2012 ◽

Vol 23 (08) ◽

pp. 1240013 ◽

Cited By ~ 7

Author(s):

MATTHEW L. BLOW ◽

JULIA M. YEOMANS

Keyword(s):

Free Energy ◽

Arbitrary Shape ◽

Liquid Surface ◽

Superhydrophobic Surfaces ◽

Surface Evolver ◽

Horizontal Section ◽

Good Convergence ◽

Cassie State ◽

Wenzel State ◽

Solid Liquid

An important feature in the design of superhydrophobic surfaces is their robustness against collapse from the Cassie–Baxter configuration to the Wenzel state. Upon such a transition a surface loses its properties of low adhesion and friction. We describe how to adapt the Surface Evolver algorithm to predict the parameters and mechanism of the collapse transition on posts of arbitrary shape. In particular, contributions to the free energy evaluated over the solid–liquid surface are reduced to line integrals to give good convergence. The algorithm is validated for straight, vertical and inclined, posts. Numerical results for curved posts with a horizontal section at their ends show that these are more efficient in stabilizing the Cassie state than straight posts, and identify whether the interface first depins from the post sides or the post tips.

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Ultrafast laser hybrid fabrication of hierarchical 3D structures of nanorods on microcones for superhydrophobic surfaces with excellent Cassie state stability and mechanical durability

Journal of Laser Applications ◽

10.2351/7.0000110 ◽

2020 ◽

Vol 32 (2) ◽

pp. 022047

Author(s):

Rui Pan ◽

Mingyong Cai ◽

Weijian Liu ◽

Xiao Luo ◽

Changhao Chen ◽

...

Keyword(s):

Ultrafast Laser ◽

Superhydrophobic Surfaces ◽

3D Structures ◽

Cassie State ◽

Mechanical Durability ◽

Laser Hybrid

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Evaporation and Condensation on Two-Tier Superhydrophobic Surfaces

ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer, Parts A and B ◽

10.1115/mnht2008-52355 ◽

2008 ◽

Author(s):

Chuan-Hua Chen ◽

Qingjun Cai ◽

Chung-Lung Chen

Keyword(s):

Superhydrophobic Surfaces ◽

Enhance Heat Transfer ◽

Evaporation And Condensation ◽

Cassie State ◽

Wenzel State ◽

Change Behavior ◽

Lotus Leaves ◽

First Time ◽

Short Carbon ◽

Nanoscale Roughness

Superhydrophobic surfaces exhibit large contact angle and small hysteresis which promote liquid transport and enhance heat transfer. Here, liquid-vapor phase change behavior is reported on superhydrophobic surfaces with short carbon nanotubes deposited on micromachined posts, a two-tier texture mimicking the surface structure of lotus leaves. Compared to one-tier microtexture which energetically favors the Wenzel state, the two-tier texture with nanoscale roughness favors the Cassie state, the desired superhydrophobic state. During droplet evaporation, the two-tier texture delays the transition from Cassie to Wenzel state. Using two-tier texture with hexadeconethiol coating, continuous dropwise condensation was demonstrated for the first time on engineered superhydrophobic surfaces.

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How Nanostructures Affect Water Droplet Nucleation on Superhydrophobic Surfaces

Journal of Heat Transfer ◽

10.1115/1.4036763 ◽

2017 ◽

Vol 139 (11) ◽

Cited By ~ 12

Author(s):

Abulimiti Aili ◽

QiaoYu Ge ◽

TieJun Zhang

Keyword(s):

Water Droplet ◽

Superhydrophobic Surfaces ◽

Experimental Investigations ◽

Nucleation Density ◽

Moderate Increase ◽

Droplet Shape ◽

Energy Applications ◽

Cassie State ◽

Droplet Nucleation ◽

Surrounding Areas

Nucleation is the first stage of phase change phenomena, including condensation on nanostructured superhydrophobic surfaces. Despite plenty of theoretical studies on the effect of nanostructure density and shape on water droplet nucleation, not many experimental investigations have been reported. Here, we show both experimentally and theoretically that a moderate increase in the nanostructure density can lead to an increase in the nucleation density of water droplets because of the decreased energy barrier of nucleation in cavities formed between the nanostructures. Specifically, we observed droplets aligned in regions with denser nanostructures. The number and average volume of the aligned droplets in these regions were larger than that of the droplets in the surrounding areas. However, nucleation in cavities subsequently caused initial pinning of the droplet base within the nanostructures, forming a balloonlike, slightly elongated droplet shape. The dewetting transition of the pinned droplets from the Wenzel state to the unpinned Cassie state was predicted by quantifying the aspect ratio of droplets ranging from 3 to 30 μm. Moreover, the coalescence-jumping of droplets was followed by a new cycle of droplet condensation in an aligned pattern in an emptied area. These findings offer guidelines for designing enhanced superhydrophobic surfaces for water and energy applications.

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HOT WATER-REPELLENT SUPERHYDROPHOBIC SURFACES WITH LONG-TERM STABILITY

Surface Review and Letters ◽

10.1142/s0218625x22500044 ◽

2021 ◽

Author(s):

JI SEONG CHOI ◽

SEONG MIN KANG

Keyword(s):

Hot Water ◽

Superhydrophobic Surfaces ◽

Water Repellent ◽

Water Droplets ◽

Long Term Stability ◽

Cassie State ◽

Potential Applications ◽

Different Temperatures ◽

Temperature Water

In this paper, we fabricate and evaluate superhydrophobic surfaces with mushroom-shaped microstructures. Using a silicon master and polymer microstructure patterning, polydimethylsiloxane (PDMS) surfaces bearing mushroom-shaped structures with five different spacing ratios are prepared and tested with water droplets of different temperatures. The fabricated PDMS surfaces demonstrate superhydrophobicity even to high-temperature water droplets with decreased surface tension. We compare the experimental data with the theoretical results calculated based on the Cassie state and Eötvös rule. Our work suggests potential applications to control wettability with liquids of various temperatures.

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