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Wettability Control Materials: Synthesis, Characterization, Properties and Applications

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: 15 August 2024 | Viewed by 2433

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Special Issue Editor

Prof. Dr. Hui Gao

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Guest Editor

School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China
Interests: functional micro-/nanomaterials; thermal protection technique for aircraft

Special Issue Information

Dear Colleagues,

Wettability control materials are of great value and can be widely used in areas such as self-cleaning, oil–water separation, anti-fog and anti-icing, anti-corrosion, anti-fouling, micro-droplet operation, microfluidics, lab-on-chip, cell engineering, etc. Understanding and engineering the surface wettability is important for promoting its application and consequently bringing huge economic benefits to society. At present, research on surface wettability control includes superhydrophobic/superhydrophilic surfaces, synthesis of micro-/nano-structures, surface chemical modification, laser processing of micro-/nano-structures, multifunctional coatings (photothermal, electro-thermal, etc.), the dynamics and phase transition characteristics of droplets on surfaces with different wettability, etc., but there is still much room for improvement. This Special Issue aims to collect the latest progress in both fundamental and applied research on various types of wettability control materials, so as to provide an exhaustive overview of the state of the art and future trends. Submissions are welcome on topics including, but not limited to, those listed below:

Micro-/nano-structured surfaces with different wettability;
Surface chemical modification methods;
Laser processing of micro-/nano-structures for wettability control;
Dynamics and phase transition characteristics of droplets on surface;
Photothermal/electro-thermal;
Mechanism of wettability control;
Applications and technological issues.

Prof. Dr. Hui Gao
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

wettability
micro-/nano-structured surface
superhydrophobic
superhydrophilic
chemical modification
laser processing
surface and interface

Published Papers (3 papers)

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Research

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13 pages, 3478 KiB

Open AccessArticle

Self-Assembled Monolayers of a Fluorinated Phosphonic Acid as a Protective Coating on Aluminum

by Zhuoqi Duan, Zaixin Xie, Yongmao Hu, Jiawen Xu, Jun Ren, Yu Liu and Heng-Yong Nie

Molecules 2024, 29(3), 706; https://doi.org/10.3390/molecules29030706 - 3 Feb 2024

Viewed by 875

Abstract

Aluminum (Al) placed in hot water (HW) at 90 °C is roughened due to its reaction with water, forming Al hydroxide and Al oxide, as well as releasing hydrogen gas. The roughened surface is thus hydrophilic and possesses a hugely increased surface area, which can be useful in applications requiring hydrophilicity and increased surface area, such as atmospheric moisture harvesting. On the other hand, when using HW to roughen specified areas of an Al substrate, ways to protect the other areas from HW attacks are necessary. We demonstrated that self-assembled monolayers (SAMs) of a fluorinated phosphonic acid (FPA, CF₃(CF₂)₁₃(CH₂)₂P(=O)(OH)₂) derivatized on the native oxide of an Al film protected the underneath metal substrate from HW attack. The intact wettability and surface morphology of FPA-derivatized Al subjected to HW treatment were examined using contact angle measurement, and scanning electron microscopy and atomic force microscopy, respectively. Moreover, the surface and interface chemistry of FPA-derivatized Al before and after HW treatment were investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS), verifying that the FPA SAMs were intact upon HW treatment. The ToF-SIMS results therefore explained, on the molecular level, why HW treatment did not affect the underneath Al at all. FPA derivatization is thus expected to be developed as a patterning method for the formation of hydrophilic and hydrophobic areas on Al when combined with HW treatment. Full article

(This article belongs to the Special Issue Wettability Control Materials: Synthesis, Characterization, Properties and Applications)

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14 pages, 3233 KiB

Open AccessArticle

Reversible Surface Energy Storage in Molecular-Scale Porous Materials

by Dusan Bratko

Molecules 2024, 29(3), 664; https://doi.org/10.3390/molecules29030664 - 31 Jan 2024

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Abstract

Forcible wetting of hydrophobic pores represents a viable method for energy storage in the form of interfacial energy. The energy used to fill the pores can be recovered as pressure–volume work upon decompression. For efficient recovery, the expulsion pressure should not be significantly lower than the pressure required for infiltration. Hysteresis of the wetting/drying cycle associated with the kinetic barrier to liquid expulsion results in energy dissipation and reduced storage efficiency. In the present work, we use open ensemble (Grand Canonical) Monte Carlo simulations to study the improvement of energy recovery with decreasing diameters of planar pores. Near-complete reversibility is achieved at pore widths barely accommodating a monolayer of the liquid, thus minimizing the area of the liquid/gas interface during the cavitation process. At the same time, these conditions lead to a steep increase in the infiltration pressure required to overcome steric wall/water repulsion in a tight confinement and a considerable reduction in the translational entropy of confined molecules. In principle, similar effects can be expected when increasing the size of the liquid particles without altering the absorbent porosity. While the latter approach is easier to follow in laboratory work, we discuss the advantages of reducing the pore diameter, which reduces the cycling hysteresis while simultaneously improving the stored-energy density in the material. Full article

(This article belongs to the Special Issue Wettability Control Materials: Synthesis, Characterization, Properties and Applications)

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Review

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27 pages, 7994 KiB

Open AccessReview

Superhydrophobic Non-Metallic Surfaces with Multiscale Nano/Micro-Structure: Fabrication and Application

by Qi Guo, Jieyin Ma, Tianjun Yin, Haichuan Jin, Jiaxiang Zheng and Hui Gao

Molecules 2024, 29(9), 2098; https://doi.org/10.3390/molecules29092098 - 1 May 2024

Viewed by 402

Abstract

Multiscale nano/micro-structured surfaces with superhydrophobicity are abundantly observed in nature such as lotus leaves, rose petals and butterfly wings, where microstructures typically reinforce mechanical stability, while nanostructures predominantly govern wettability. To emulate such hierarchical structures in nature, various methods have been widely applied in the past few decades to the manufacture of multiscale structures which can be applied to functionalities ranging from anti-icing and water–oil separation to self-cleaning. In this review, we highlight recent advances in nano/micro-structured superhydrophobic surfaces, with particular focus on non-metallic materials as they are widely used in daily life due to their lightweight, abrasion resistance and ease of processing properties. This review is organized into three sections. First, fabrication methods of multiscale hierarchical structures are introduced with their strengths and weaknesses. Second, four main application areas of anti-icing, water–oil separation, anti-fog and self-cleaning are overviewed by assessing how and why multiscale structures need to be incorporated to carry out their performances. Finally, future directions and challenges for nano/micro-structured surfaces are presented. Full article

(This article belongs to the Special Issue Wettability Control Materials: Synthesis, Characterization, Properties and Applications)

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