Wetting and Dewetting Transitions on Submerged Superhydrophobic Surfaces with Hierarchical Structures

Wu, Huaping; Yang, Zhe; Cao, Bisong; Zhang, Zheng; Zhu, Kai; Wu, Biao; Jiang, Shaofei; Chai, Guozhong

doi:10.1021/acs.langmuir.6b03752

Cited by 60 publications

(49 citation statements)

References 53 publications

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“…[ 25–27 ] Additionally, the surface chemical composition and geometric morphology can also affect surface wettability. [ 28–36 ] By adjusting the surfaces with wettable gradients (such as structural gradients and chemical gradients), [ 37–39 ] asymmetric structures [ 40–44 ] or bioinspired structures, [ 45–51 ] a droplet spreading on these surfaces can be well manipulated. However, singly structural or chemical gradient surfaces can just carry out the conversion of surface wetting properties between hydrophobic and hydrophilic (or between hydrophobic and super‐hydrophilic) but not favor the droplet to spread or move over a long distance due to the influence of the intrinsic contact angle.…”

Section: Introductionmentioning

confidence: 99%

Large‐Range, Reversible Directional Spreading of Droplet on a Double‐Gradient Wrinkled Surface Adjusted Under Mechanical Strain

Chai

Tian

et al. 2020

Adv Materials Inter

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Dynamical regulation to unidirectional wetting has received considerable attention in recent years due to its important role in flexible electronics, microfluidics, drug transportation, and so forth. It is of great significance to prepare a surface which allows the droplet to spread directionally on it with the length of droplet reversibly fluctuated within a broad range under external stimulation. In this paper, a double‐gradient wrinkled structure is prepared by constructing the structure‐gradient pillar arrays on a mechanics‐adjusted wrinkled surface and subsequently making chemical gradient by oxygen plasma treatment. Under the synergistic effect of the structural gradient, chemical gradient, and wrinkled structure, the droplet can undergo unidirectional spreading and realize dynamic regulation of the spreading length on the flexible structure. This will provide a propagable method for the regulation of surface wetting.

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Section: Introductionmentioning

confidence: 99%

Large‐Range, Reversible Directional Spreading of Droplet on a Double‐Gradient Wrinkled Surface Adjusted Under Mechanical Strain

Chai

Tian

et al. 2020

Adv Materials Inter

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“…Surfaces with microstructures such as micro-pillars and micropores have some applications in fabrication of superhydrophobic or superhydrophilic surfaces and oil/water inside the rocks [23][24][25][26][27][28][29]. Yuan et al [24,[30][31] elegantly studied the wettability of patterned surfaces.…”

Section: Introductionmentioning

confidence: 99%

Evaporation of ethanol/water mixture droplets on micro-patterned PDMS surfaces

Huang

Sun

et al. 2019

International Journal of Heat and Mass Transfer

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We report evaporation of ethanol/water mixture droplets on both pillar-arrayed and micro-holed polydimethylsiloxane (PDMS) surfaces. Analysis of wettability shows that (i) when the pillar-to-pillar spacing is 5 lm, the pillar-arrayed PDMS surfaces are Cassie-Baxter-wetted; (ii) when the pillar-to-pillar spacing is 20 or 50 lm, part of each pillar-arrayed surface is Cassie-Baxter-wetted while the other part Wenzelwetted; (iii) all micro-holed PDMS surfaces are Cassie-Baxter-wetted; (iv) the advancing and receding contact angles increase with the increase of the pillar-to-pillar spacing, while they decrease with the increase of the hole-to-hole spacing. The investigation on evaporation of mixture droplets demonstrates that (i) evaporation on pillar-arrayed PDMS first proceeds with constant contact radius mode (CCR) due to the strong adhesion between the surface and the droplet; (ii) on micro-holed surfaces CCR stage is also observed for the surface with the hole-to-hole spacing of 5 lm, while it is not found at high ethanol concentration for surfaces with the hole-to-hole spacings of 20 lm and 50 lm, which is attributed to the weak adhesion between the micro-holed surfaces and the droplet. Finally, the evolution of droplet volume and its two-third power are discussed.

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“…It was noticeable that the interface of water and the captured gas reached to a state of equilibrium and force balance. According to Laplace equation, the pressure balance of liquid/vapor interface underwater at equilibrium state can be deduced as

P_{normalV} - P_{0} - P_{normalL} = \frac{2 γ_{LV}}{r}

where P V is the pressure of the trapped air among surface microstructures, P 0 is the ambient gas pressure, P L is the water pressure correlated with the depth from atmospheric water surface, γ LV is the interfacial free energy between the liquid–vapor, r is the curvature radius of liquid/vapor curve interface (Figure 5e). The pressure difference, Δ P , between P 0 and P V can be deduced from Equation

Δ P = P_{normalV} - P_{0} = P_{normalL} + \frac{2 γ_{LV}}{r}

…”

Section: Resultsmentioning

confidence: 99%

Trapped Air‐Induced Reversible Transition between Underwater Superaerophilicity and Superaerophobicity on the Femtosecond Laser‐Ablated Superhydrophobic PTFE Surfaces

Huo

Yong

Chen

et al. 2019

Adv Materials Inter

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Controlling the behavior of underwater bubbles on a solid surface and establishing the contact model between a gas bubble and a solid substrate in a water medium have great significance. Herein, a method is proposed to realize the reversible switching between underwater superaerophilicity and superaerophobicity on the femtosecond laser‐induced rough polytetrafluoroethylene (PTFE) surface by controlling the trapped air layer in water. The original femtosecond laser‐structured PTFE surface is superhydrophobic in air and superaerophilic in water. After vacuum‐pumping treatment, the trapped air layer around the microstructures of the underwater superhydrophobic PTFE surface is removed, leading to the underwater superaerophobicity of the sample surface. The trapped air layer can be recovered and the PTFE surface can regain the underwater superaerophilicity by drying treatment and the immersion of the sample in water again. Such a round‐trip transition can achieve the bubble's “locating capture” and the control of the selective passage of air bubbles through a perforated rough PTFE sheet. It is believed that the resultant underwater superaerophobic and superaerophilic surfaces will have significant applications in manufacturing submarine gas‐collection devices, improving the chemical reaction between liquid reagent and gas, and avoiding the microchannel blockage caused by bubbles in microfluidics and biosensor devices.

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Wetting and Dewetting Transitions on Submerged Superhydrophobic Surfaces with Hierarchical Structures

Cited by 60 publications

References 53 publications

Large‐Range, Reversible Directional Spreading of Droplet on a Double‐Gradient Wrinkled Surface Adjusted Under Mechanical Strain

Large‐Range, Reversible Directional Spreading of Droplet on a Double‐Gradient Wrinkled Surface Adjusted Under Mechanical Strain

Evaporation of ethanol/water mixture droplets on micro-patterned PDMS surfaces

Trapped Air‐Induced Reversible Transition between Underwater Superaerophilicity and Superaerophobicity on the Femtosecond Laser‐Ablated Superhydrophobic PTFE Surfaces

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