Recent Progresses of Superhydrophobic Coatings in Different Application Fields: An Overview
Round 1
Reviewer 1 Report
It's hard to write a good review. The most important thing is to define your goal well, and then implement it in such a way that will interest the reader. There are a lot of reviews about hydrophobic materials. In order for the manuscript to be original and interesting for readers, the purpose of the work must be particularly well thought out.
The purpose of this work was defined as “...highlight the recent progresses on superhydrophobic coatings in automobile, marine, aircraft, solar energy, architecture, electronics and appliances fields, and discuss the requirement in these vital fields. (…)This review serves as a good reference source and provides insight for the design and optimization of superhydrophobic coatings for different applications”. It seems to me that the manuscript does not quite fulfill its purpose.
The main aim of hydrophobic materials is significant water resistance. This property is no longer satisfactory nowadays if it is not accompanied by additional added properties useful in specific applications. For example, in applications in the automotive industry, the coating on the car glass, apart from the fact that it is simply supposed to reduce the wettability of the glass, must also have adequate transparency, but it would be good if it also facilitates self-cleaning and, for example, should be anti-reflective. The same requirements apply to coatings for solar PV panels, solar collectors or electronics. If the coating is to be used on a car body, in addition to reducing wettability, it would also increase corrosion resistance and, for example, improve abrasion resistance, it can also be antibacterial - why not. Such features are also important for aicraft or marine applications.
The division of the work into chapters on the scope of industrial applications causes the authors to repeat themselves or that the reader has the impression that certain coating features according to the authors, are important only in some applications and are irrelevant in others. It is not understandable, for example, why the authors write about the difficulty of combining the appropriate roughness of the coating (necessary to achieve hydrophobic properties) with the simultaneous preservation of optical transmittance in the chapter "Solar photovoltaic (PV) panel". Why don't they write about this problem, for example in the chapter "Wind shields"?.
In each chapter, the authors describe in some detail the materials that can be used to make hydrophobic coatings in a given range of applications. Therefore, the reader gets tired of repeating the tech descriptions of the same types of materials used in the context of different application possibilities. For example, SiO2 nanoparticles (unmodified or surface modified) are described in virtually every chapter.
Taking the above arguments into account, I think it is advisable to rethink the structure of the manuscript. I believe that the authors have a lot of knowledge about hydrophobic coatings, but in addition to demonstrating this knowledge, you also need originality. I believe that the authors unnecessarily show the lotus leaf image and unnecessarily create a separate chapter devoted to theoretical considerations of the foundations of the phenomenon of superhydrophobicity. It was already in other articles - this is not what the reader is looking for in an article from the end of 2020. After all, the reader can open any older article or even an academic textbook. The reader expects an original approach to the issue. It expects the authors' help in understanding the complexity of contemporary requirements for hydrophobic coatings that are to be used in specific industries. In my opinion, at the beginning a chapter would be needed that would show what added values (apart from the high contact angle) the coating must have (or may have) in a specific industrial (or everyday) application. In this way, it might be possible to avoid repetitions, because it would be clear that, for example, the added value of transparency, for example, is necessary in applications for car windows, but also in the case of PV panels or electronic displays. Such an additional criterion, imposed in some applications, would also give a good introduction to the description of the materials useful for meeting it e.g. in the case of the necessity to maintain transparency, the use of metal nanoparticles is excluded.
The manuscript also contains a number of inaccuracies that should be corrected. I am listing only some inaccuracies:
- „Many methods can be used to achieve such hierarchical structures, such as templating [14], etching [15-16], anodization [17], electrodeposition [18], sol-gel [19-20], self-assembling [21], dip coating [22-23] and spray coating [24-25].” The authors confuse the methods of applying coatings (dip coating, spin coating) with the methods of producing materials (sol-gel).
- „A. Syafiq et al. [37] synthesized a self-cleaning transparent coating by utilizing organic PDMS and Sylgard polymers, inorganic nano- CaCO3 fillers and the Aminopropyl triethoxysilane (APTES) binder.” Capital letters should not be used for the names of chemicals unless they are the first word of a sentence
- „The hollow silica coatings realized a transition from superhydrophilic to supherhydrophobic state after hydrophobic modification with PFDTES using chemical vapor deposition (CVD) method” The coating was not hollow. The silica from which the coating was formed was hollow.
- „In practical applications, the materials used for car bodies are mainly steel, aluminum, magnesium and their alloys, etc. „ Steel is an alloy - so what steel alloy is it? Pure metals are not used in the construction of vehicles, but rather their alloys.
Summing up, I propose to rebuild the work (change its structure) so as to avoid repetition related to discussing the same groups of materials in different applications. After such changes, the work should be reassessed by the reviewers.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The review by Bai et al. on the fabrication of superhydrophobic coatings withs different applications is a very nice piece of works, and only some additional references should be included before publication:
-Superhydrophobic films in marine environment: Coatings 2020, 10, 578; Coatings 2019, 9, 303; Colloids Surf. A 2016, 505, 158-164; Colloids Surf. B 2016, 137, 167-175; Colloid Surf. A 2015, 480, 369-375
-General LbL: Adv. Colloid Interface Sci. 2020, 282, 102197
-Prorection solar panels: Adv. Colloid Interface Sci. 2020, 286, 102309
Author Response
please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
This study reports "Recent progress of superhydrophobic coatings in different application fields: an overview". There are a lot of relevant review articles already published in the research field. However, the authors claim that this review has novelty by focusing on the applications of superhydrophobic coatings discussed in different fields, including automobile, marine, aircraft, solar energy, architecture, electronics, and appliances. To prove the uniqueness of this review paper, however, the following issues should be addressed.
1) Although the authors assorted the sections based on the applications, required coating properties are almost same, regardless of the applications. All of the coating characteristics are expressed by contact angle, slide angle, durability, and transparency for some application. Then, what are the requirements or characteristics to specify the applications? If no specific requirements are needed and only superhydrophobicity and durability are all the required factors regardless of the applications, there may be no need to classify the sections depending on the application. Please clarify this and provide/compare the specific requirements or characteristics to the proposed applications.
2) A represented figure is needed in each sub-section. Please provide a figure in the section of 3.1.1 and 3.1.2.
3) In page 14 at line 21, remove a bracket.
4) A title for a section of 3.4 is missing. It may be for “solar energy”.
5) The authors used the figure 17 twice in separate sections. No need to use the same figure. Please remove one of those or modify the one.
Author Response
please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript “Recent progresses of superhydrophobic coatings in different application fields: an overview „ has been revised as suggested. It may be published in Coatings as it stands. This work is an interesting and comprehensive summary of the requirements for hydrophobic materials in various areas of their application.
Author Response
Thanks again for reviewer' comments and acknowledgement on the manuscript.
Reviewer 3 Report
All of the comments are now clearly answered. Thank you for your response.
Author Response
Thanks again for reviewer' comments and acknowledgement on the manuscript.
