Why Condensate Drops Can Spontaneously Move Away on Some Superhydrophobic Surfaces but Not on Others

Feng, Jie; Pang, Yichuan; Qin, Zhaoqian; Ma, Ruiyuan; Yao, Shuhuai

doi:10.1021/am301767k

Cited by 125 publications

(111 citation statements)

References 36 publications

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“…In principle, any sub-microscale structures with a small feature size (tip size and interspace) and a certain height (or depth) can become effective candidates for creating CMDSP surfaces. In fact, except for arrays of closely packed nanotips, including nanocones, [22,27,50,69,70] nanoneedles, [21,28,31,66,71] nanopencils, [23] and tip-like nanotubes, [72,73] other architectures such as nano wires, [24,74] nanosheet arrays, [20,29,62,75] nanorod-capped nano pores, [68,76] the porous structure of nanoparticles, [67] nanoparticle aggregates, [73,[77][78][79][80] and two-tier structures [25,57,63,[81][82][83][84][85][86][87][88][89] have all been verified to be effective in endowing material surfaces with the desired CMDSP functionality as long as they follow these basic construction rules.…”

Section: Construction Rules Of Bionic Cmdsp Surfacesmentioning

confidence: 99%

“…Similarly, various wetchemistry methods have been developed for the in situ growth of bionic CMDSP nanostructures on the surfaces of metal materials. [20][21][22][23][24][27][28][29]31,[66][67][68]70,[72][73][74][75][76]87] It is known that copper and aluminum are the most widely used metal materials, and the latest advances in their surface functionalization have shown remarkable potential in energy-related applications. Accordingly, we will briefly review recent progress in metal-based CMDSP surfaces.…”

Section: Metal-based Cmdsp Surfacesmentioning

confidence: 99%

“…The in situ grown copper oxide sheet-like nanostructures (Figure 3d) can also render CMDSP functionality. [20,29,62,75] In addition, a type of hierarchical microand nanostructure [83] was presented by the in situ growth of copper oxide nanowires on patterned copper microposts, which shows CMDSP functionality after hydrophobic treatment.…”

Section: Copper-based Cmdsp Surfacesmentioning

confidence: 99%

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Recent Progress in Bionic Condensate Microdrop Self‐Propelling Surfaces

2017

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interest has focused on utilizing the lowadhesivity nature of superhydrophobic surfaces for the rapid removal of condensate microdrops, as this has significance in fundamental research and technological innovation. Example applications are the enhancement of condensation heat transfer for high-efficiency thermal management and energy utilization, [20][21][22][23][24][25] energy-effective antifreezing for airconditioner heat exchangers and aircraft wings, [26][27][28] and electrostatic energy harvesting. [29] In general, condensate drops on typical flat hydrophobic surfaces are only shed off under gravity when their sizes are comparable to the capillary length (≈2.7 mm for water), [30] which creates undesirable effects such as large thermal resistance [20][21][22][23][24][25] and the freezing of subcooled drops. [26][27][28] Clearly, a great challenge is the timely removal of condensate drops at the microscale where the gravitational effect does not work. The latest research has indicated that these small-scale condensate microdrops may self-remove via mutual coalescence as long as the coalescence-released excess surface energy is larger than the interface adhesion-induced energy dissipation. [31] Much effort has been devoted to exploring the utilization of knowledge of bionic low-adhesivity superhydrophobicity to develop innovative condensate microdrop self-propelling (CMDSP) surfaces. Different from traditional superhydrophobic surfaces, which are characterized by the bouncing or rolling off of deposited millimeter-size large drops, [32,33] CMDSP surfaces support the self-removal capability of smallscale condensate microdrops. It has been reported that classical superhydrophobic lotus leaves (Figure 1a), [34][35][36][37] as well as artificial surfaces consisting of hierarchical micro-and nanostructures, [38] one-tier microstructures, [39][40][41][42][43] or nanostructures [44,45] with larger characteristic interspaces, present a low-adhesivity property to the deposited water macrodrops, but become highly adhesive to condensed microdrops (Figure 1b). This is because moisture easily penetrates the microscale valleys or cavities. Clearly, superhydrophobic surfaces with irrationally designed surface structures can enhance the solid-liquid interfacial adhesion instead of promoting the rapid removal of condensed drops. Accordingly, it is still a challenge to design and fabricate very effective low-adhesivity superhydrophobic surfaces with the self-removal ability of condensate microdrops. Recently, there has been a large breakthrough in understanding the mechanism and construction rules of bionic CMDSP surfaces, leading to the exploration of fabrication methods for the surface functionalization of widely used metal materials and the Bionic condensate microdrop self-propelling (CMDSP) surfaces are attracting increased attention as novel, low-adhesivity superhydrophobic surfaces due to their value in fundamental research and technological innovation, e.g., for enhancing heat transfer, energy-effective antifreezing, and...

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Section: Construction Rules Of Bionic Cmdsp Surfacesmentioning

confidence: 99%

Section: Metal-based Cmdsp Surfacesmentioning

confidence: 99%

Section: Copper-based Cmdsp Surfacesmentioning

confidence: 99%

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Recent Progress in Bionic Condensate Microdrop Self‐Propelling Surfaces

2017

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“…Therefore, it is highly desirable to develop hybrid surfaces that are compatible with materials commonly employed for heat transfer applications, such as copper. To the best of our knowledge, studies of dropwise condensation on copper substrates have exclusively focused on nano-structured surfaces; [25][26][27] condensation dynamics on copper surfaces with hierarchical surface structures have not been explored.…”

mentioning

confidence: 99%

“…[19] Thus, the synergistic cooperation between the micro and nanoscale roughnesses on the hierarchical surface eases condensate droplet departure from the surface. Lastly, when the condensate droplet grows in a position resting on the inclined posts (Figure 4d), the Laplace pressure is expressed as: [27,44,45] …”

mentioning

confidence: 99%

Exploiting Microscale Roughness on Hierarchical Superhydrophobic Copper Surfaces for Enhanced Dropwise Condensation

Chen

Weibel

Garimella

2015

Adv Materials Inter

111

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Condensation of water vapor is of great interest in thermal management [1] and power generation [2] owing to the improved heat transfer by phase change, and in desalination [3] and dew/fog harvesting [4,5] systems for its ability to extract vapor from carrier gases. Enhancement of the condensation heat and mass transfer processes in these systems could lead to considerable performance gains, economic return, and energy savings. Heterogeneous condensation is dramatically influenced by the physical structure and chemical properties of a surface. Depending on the surface wettability, water vapor can condense on a surface either as a continuous liquid film (filmwise) or as individual droplets (dropwise). It is reported that dropwise condensation can produce heat transfer coefficients that are an order of magnitude higher than in filmwise condensation. [6] To attain this performance, condensed droplets must be rapidly removed from the surface and fresh spaces on the substrate exposed for nucleation; otherwise, accumulated large droplets will act as a thermal barrier and inhibit the heat/mass transfer rate. [7] To promote removal of condensate droplets, the droplet adhesion to the substrate must be minimized. Structured superhydrophobic surfaces [8][9][10][11][12] could offer an ideal

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