Wetting of Silicon Nanograss: From Superhydrophilic to Superhydrophobic Surfaces

Dorrer, Christian; Rühe, Jürgen

doi:10.1002/adma.200701140

Cited by 227 publications

(216 citation statements)

References 27 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%

“…Benefiting from the wellestablished top-down micro-and nanofabrication technologies, various silicon nanostructures (e.g., nanoneedles [71,90] and nanocones [69] ) and their combination with regular microstructures (e.g., micropillars [25,85] and micropyramids [84] ) have been successively made for creating bionic CMDSP surfaces, and the transport behaviors of condensate microdrops at the microscale showing the typical coalescence-induced self-propelling details of condensed microdrops on the nanoneedle surface. f,g) Reproduced with permission.…”

Section: Metal-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%

Recent Progress in Bionic Condensate Microdrop Self‐Propelling Surfaces

2017

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“…The use of superhydrophobic surfaces in the dropwise condensation has led to the observation of the rapid motion of liquid droplet driven by the coalescence. [6][7][8][9] Such a phenomenon is believed to be powered by the surface energy released during the drop coalescence. Boreyko and Chen 6 did a simple scaling analysis by assuming that all the released surface energy is converted to kinetic energy of the merged droplet.…”

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confidence: 99%

Size effect on the coalescence-induced self-propelled droplet

Wang

Yang

Zhao

2011

Applied Physics Letters

225

233

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Surface charge density model for predicting the permittivity of liquid mixtures and composites materials J. Appl. Phys. 111, 064101 (2012) Energy dissipation in non-isothermal molecular dynamics simulations of confined liquids under shear J. Chem. Phys. 135, 134708 (2011) Extension of the Steele 10-4-3 potential for adsorption calculations in cylindrical, spherical, and other pore geometries J. Chem. Phys. 135, 084703 (2011) Melting of iron at the Earth's core conditions by molecular dynamics simulation AIP Advances 1, 032122 (2011) Equilibrium structure of the multi-component screened charged hard-sphere fluid

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“…Combined with a faster growth rate for individual droplets, this ordered droplet nucleation process increases the probability for coalescence of multiple droplets in the interstices between micro-posts (in comparison to the random coalescence events that occur on the more homogeneous nano-structured surface). Second, the presence of nanoscale roughness on the hierarchical surface increases the local condensate droplet contact angle , [18,42,43] which reduces the work of adhesion ( ad W ) of the droplet to the surface…”

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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Wetting of Silicon Nanograss: From Superhydrophilic to Superhydrophobic Surfaces

Cited by 227 publications

References 27 publications

Recent Progress in Bionic Condensate Microdrop Self‐Propelling Surfaces

Recent Progress in Bionic Condensate Microdrop Self‐Propelling Surfaces

Size effect on the coalescence-induced self-propelled droplet

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

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