Tunable Wetting Patterns on Superhydrophilic/Superhydrophobic Hybrid Surfaces for Enhanced Dew‐Harvesting Efficacy

Hou, Kongyang; Li, Xiaoyang; Li, Qiang; Chen, Xuemei

doi:10.1002/admi.201901683

Cited by 53 publications

(49 citation statements)

References 53 publications

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“…[ 67,68 ] Through controlling the laser scanning speed and scanning track, nonuniform microstructures with the desired arrangement are easily obtained, generating heterogeneous wettability on surfaces. [ 69,70 ] Note that during the ablation process, nanostructures are formed, along with the desired microstructures. The formed hierarchical micro/nanostructures enhance the wettability and exhibit superhydrophobicity or superhydrophilicity on the surface.…”

Section: Construction Methodologymentioning

confidence: 99%

Heterogeneous Wettability Surfaces: Principle, Construction, and Applications

Liu

Zhao

et al. 2020

Small Structures

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Surface wettability plays a vital role in liquid-solid-gas systems and has elicited increasing research interest in numerous fields, including self-cleaning, optics and electronics, sensing and detection, heat management, and microfluidics. [1-5] For example, superhydrophobic surfaces, such as the lotus leaf, show minimized adhesion force to water. Water droplets can freely roll off this type of surface and remove dust, granting the surface with a self-cleaning property. [6,7] By comparison, a water drop placed on a hydrophilic surface forms a liquid puddle, with the solutes in the liquid finally deposited on the surface after drying. This is the fundamental mechanism for various printing and lithography techniques for material deposition. [8-10] However, these uniform surfaces fail to meet the rigorous requirements in complex conditions, such as high-resolution functional material patterning and enrichment for parallel detection. Alternatively, heterogeneous wettability substrates with rationally designed water-repellent and water-loving properties can be utilized to satisfy these fastidious requirements. Different regions on such surfaces have distinct wettability, thus exhibiting excellent capability in precisely regulating the solid-liquid interactions. A representative example is the splendid water manipulation of the desert beetle, Stenocara, using the heterogeneous wettability strategy to collect and transport water for survival in the Namib Desert, which is one of the driest places in the world. The hydrophilic bumps distributed on the hydrophobic back of the beetle can capture fog in the moist morning and condensate it into large water droplets. Then, the hydrophobic region serves as a pathway to guide the water droplets rolling to its mouth. [11] This idea has greatly inspired the design and utilization of heterogeneous wettability for various applications. Generally, the terms "hydrophilic" and "hydrophobic" are used to describe the state of a solid surface when contacting with water. If the water droplet contact angle is larger than 90 , the surface is hydrophobic; otherwise the surface is hydrophilic. However, when relating to dynamic liquid manipulation on solid surfaces, the key factor is the solid-liquid adhesion force instead of the hydrophilicity/hydrophobicity. For example, when a water droplet impacts on a hydrophobic and high-adhesive surface equipped with a hydrophilic and low-adhesive stripe, it can be split into two subdrops, which is direct evidence for the solid-liquid adhesion force dominating the liquid's dynamic behavior. [12] Although in many cases, the solid-liquid adhesion force decreases with enhancement of hydrophobicity, for example, the adhesion force on a superhydrophobic surface is much smaller than that on a hydrophilic surface, there exist exceptions, such as a hydrophilic surface having a smaller adhesion force than a hydrophobic surface. [13] Therefore, in these cases the heterogeneous wettability mainly indicates the nonuniformity in the adhesion force. Levkin and cowork...

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Section: Construction Methodologymentioning

confidence: 99%

Heterogeneous Wettability Surfaces: Principle, Construction, and Applications

Liu

Zhao

et al. 2020

Small Structures

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“…Hou et al proposed a facile and reliable method to fabricate superhydrophilic triangular array on copper substrates (Figure 11b). [125] By wet-etching process and silane treatment, the superhydrophobic copper surfaces were first created. Then superhydrophilic triangular array was selectively inscribed by laser-engraving.…”

Section: Wedge-shaped Combination Gradientsmentioning

confidence: 99%

“…Reproduced with permission. [125] Copyright 2020, Wiley-VCH GmbH. c) Fabrication processes of cactus kirigami with triangle-shaped combination gradients via laser cutting and hydrophobic modification.…”

Section: Wedge-shaped Combination Gradientsmentioning

confidence: 99%

“…[122] The superhydrophilic triangular patterns in the work of Hou et al can fast condensate droplet nucleation, directional delivery, and efficient departure, which can be used for dew harvesting. [125] Apart from these traditional metallic materials, the common low-cost paper designed in Figure 11c can simplify the cactusinspired fog collection spines from 3D cone to 2D triangle. [130] It was noted that the arrangement of the spines will influence fog collecting, so two distinct cactus kirigami structures including symmetric and alternative arrangements were compared ( Figure 13b).…”

Section: Fog/water Collectionmentioning

confidence: 99%

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Laser Fabrication of Bioinspired Gradient Surfaces for Wettability Applications

Yin

Xiao

et al. 2021

Adv Materials Inter

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materials with gradients inspired by biological surfaces has therefore attracted much interest. Strategies for preparing gradient surfaces include vapor-phase diffusion, gradual immersion, electrochemical oxidation, and photolithography that have broadly adopted. [20-26] However, their material constraints, tedious and time-consuming processes, and their single-pattern limit their widespread use. Developing a substrate-independent, facile and efficient, pattern-diverse method for preparing gradient surfaces would aid fundamental science and practical application. Among various techniques, laser processing has recently emerged as a powerful tool in integratedoptics and biomimetic micro-nanodevices. This technology can be used to precisely control the preparation of micro/nanoscale structures on various substrates such as metals, glass, ceramics, and polymers. [27-33] Besides, the high energy density of lasers allows the machining process to be completed quickly and efficiently. Combining laser machining with computer-aided control allows laser ablation parameters to be precisely controlled, including the processing position, scanning speed, scanning interval, and scanning track. Laser processing can therefore be used to produce flexible and diverse patterns in complex workpieces. And laser micro/nano fabrication has been applied to regulate surface wettability. [34-43] Therefore, laser processing has great potential for developing samples with different wettability and geometries on various materials. This review discusses laser fabrication of bioinspired gradient surfaces for wettability applications, whose overview is shown in Figure 1. The related backgrounds including gradient surfaces in natural creatures, the theoretical basis of wettability, and the distinct characteristics of laser processing are introduced. Gradient surfaces can be classified into wettability gradients and geometric gradients, and they are discussed in terms of various laser fabrication approaches and wettability applications. It is worth mentioning the definition of wettability gradient and geometric gradient in this review. Wettability gradient is defined as a surface with no obvious geometric change in the shape, and there is a difference of contact angles on the macro level resulting from the roughness gradient on the micro level. Geometric gradient is defined as a surface possessing significant geometric changes in the shape, but not much difference in the roughness of the entire surface at the microscopic level. Specially, a wettability gradient surface generates a water driving force as a result of its varying surface roughness. Wettability gradient surfaces can be applied in water droplet control, Inspired by nature, gradient surfaces have attracted broad research interest because of their potential in microfluidics, fog/water collection, and water electrolysis. Among the various techniques for preparing gradient surfaces, laser processing is substrate-independent, facile and efficient, patterndiverse, which can be used to prepare...

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“…In nature, a number of plants and insects have developed ingenious strategies to fulfill specific goals such as self-cleaning properties (Lotus leaves) (Barthlott and Neinhuis, 1997) and water collection abilities (Namib desert beetles) (Parker and Lawrence, 2001). These properties have in common the creation of highquality sliding surfaces, which usually exhibit great droplet self-removal ability and can partially satisfy the requirements of effective water harvesting above (Wei et al, 2014;Hou et al, 2020). However, the water removal on such surfaces is generally driven by gravity against pinning forces, usually resulting in an unignorable waiting time and considerable evaporation loss (Beysens, 2018).…”

Section: Introductionmentioning

confidence: 99%