Functional superhydrophobic surfaces made of Janus micropillars

Mammen, Lena; Bley, Karina; Papadopoulos, Periklis; Schellenberger, Frank; Encinas, N.; Butt, Hans‐Jürgen; Weiss, Clemens K.; Vollmer, Doris

doi:10.1039/c4sm02216e

Cited by 27 publications

(23 citation statements)

References 59 publications

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“…Many superhydrophobic surfaces rely on microstructures (33). As a model, we investigated microstructured superhydrophobic surfaces that were made of SU-8 micropillars (rectangular, 10-mm height with 5 × 5-mm 2 top areas; center-center distance of pillars, 20 mm) on glass slides using photolithography.…”

Section: Microstructured Surfacesmentioning

confidence: 99%

When and how self-cleaning of superhydrophobic surfaces works

et al. 2020

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Despite the enormous interest in superhydrophobicity for self-cleaning, a clear picture of contaminant removal is missing, in particular, on a single-particle level. Here, we monitor the removal of individual contaminant particles on the micrometer scale by confocal microscopy. We correlate this space-and time-resolved information with measurements of the friction force. The balance of capillary and adhesion force between the drop and the contamination on the substrate determines the friction force of drops during self-cleaning. These friction forces are in the range of micro-Newtons. We show that hydrophilic and hydrophobic particles hardly influence superhydrophobicity provided that the particle size exceeds the pore size or the thickness of the contamination falls below the height of the protrusions. These detailed insights into self-cleaning allow the rational design of superhydrophobic surfaces that resist contamination as demonstrated by outdoor environmental (>200 days) and industrial standardized contamination experiments.

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Section: Microstructured Surfacesmentioning

confidence: 99%

When and how self-cleaning of superhydrophobic surfaces works

et al. 2020

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Section: Wettability Of (Mof) Surfacesmentioning

confidence: 99%

Hydrophobic Metal–Organic Frameworks

et al. 2019

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formed from organic ligands and metal cations. [1][2][3][4][5][6][7][8][9][10] They are typically synthesized under mild conditions via coordinationdirected self-assembly processes and are also known as metal-organic coordination networks and porous coordination polymers. [11][12][13][14] Due to their high surface areas, large porosity, tunable pore sizes, and functionalities, MOFs have prospective applications in fields such as gas storage/separation, sensing or recognition, proton conduction, and magnetism. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] However, the advantageous unique structural features of even some of the best-performing MOFs are readily degraded because of their high moisture sensitivity, which may limit their practical applications. [29][30][31][32] Consequently, there is an ongoing search for highly hydrophobic, porous, sorbent materials to be employed in various large-scale applications in industry such as oil spill cleanup, hydrocarbon storage/separation, or water purification. [33][34][35][36][37] Many academics, industrial scientists, and engineers have therefore conducted research on the fabrication of superhydrophobic surfaces, which involves hydrophobic surface modification and creating surface roughness on the micrometer-or nanoscale. Hydrophobic surfaces are defined as substrates with an apparent contact angle greater than 90° with respect to water. On superhydrophobic materials, water droplets have contact angles above 150° and show very low adhesion because the drops partially rest on an air cushion. The surface energy and roughness govern the wettability of hydrophobic surfaces. In general, lower surface energies and higher roughness are associated with larger contact angles, lower contact angle hysteresis, and robust superhydrophobicity. Because of their ultralow surface energies (10-20 mN m −1 ), alkyl-based or fluorinated compounds are commonly used as hydrophobic modifiers to prepare surfaces with high intrinsic contact angles (>90°). [33][34][35][36][37][38][39][40][41][42] Recently, few methods have been developed for synthesizing hydrophobic MOFs including both pristine and composite systems. This review offers a comprehensive overview of the state of the art in hydrophobic MOF synthesis and the field's challenges and opportunities. Various synthetic strategies for preparing hydrophobic MOFs and their composites are introduced. We discuss the basics of wetting and critical challenges in the characterization of these hydrophobic materials. The potential applications of hydrophobic MOFs and related Metal-organic frameworks (MOFs) have diverse potential applications in catalysis, gas storage, separation, and drug delivery because of their nanoscale periodicity, permanent porosity, channel functionalization, and structural diversity. Despite these promising properties, the inherent structural features of even some of the best-performing MOFs make them moisture-sensitive and unstable in aqueous media, limiting their practical usefulness. This problem could be ...

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“…For instance, many applications, such as sensors, tunnel field‐effect transistors, light emitting diodes, photovoltaics, and photonics, require or would benefit from an axial homo‐ or heterojunction and electrical communication between the segments with, e.g., different catalytic or surface properties. The ability to create semiconductor wires and wire arrays with axial heterostructures has been demonstrated and the feasibility of creating bi‐functionalized semiconductor wires and wire arrays has been reported previously for their use in photocatalysis and microfluidics, or as superhydrophobic surfaces . However, a combination of heterostructured wires with functionalized surfaces is rare, mainly because their preparation is complex and requires several steps.…”

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confidence: 99%

“…However, a combination of heterostructured wires with functionalized surfaces is rare, mainly because their preparation is complex and requires several steps. So far, bi‐functionalized wires have been created by physically masking the part of the wire that was to remain unmodified . Typically, wires are embedded completely in a polymeric material first, which is then subsequently etched back to expose parts of the wires for further functionalization.…”

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confidence: 99%

Spatioselective Electrochemical and Photoelectrochemical Functionalization of Silicon Microwires with Axial p/n Junctions

et al. 2015

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The spatioselective functionalization of silicon microwires with axial p/n junctions is achieved using the electronic properties of the junction. (Photo)electrochemical deposition of metals is demonstrated at the bottom and top of the wires in the dark and light, respectively. The junction depletion layer remains unmodified, which allows its visualization and comparison with theoretical calculations.

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Functional superhydrophobic surfaces made of Janus micropillars

Abstract: Particle coated micropillar arrays having hydrophobic sidewalls and hydrophilic silica tops are fabricated, enabling the top sides to be selectively post-functionalized. The so termed Janus pillars remain in the Cassie state even after chemical modification of the top faces.

Cited by 27 publications

References 59 publications

When and how self-cleaning of superhydrophobic surfaces works

When and how self-cleaning of superhydrophobic surfaces works

Hydrophobic Metal–Organic Frameworks

Spatioselective Electrochemical and Photoelectrochemical Functionalization of Silicon Microwires with Axial p/n Junctions

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