Superamphiphobic Surfaces E-Book
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- Sprache: Englisch
A definitive resource on superamphiphobic surfaces, covering their fabrications, characterizations, practical applications, challenges, and future directions
Superamphiphobic Surfaces: Fabrication, Characterization, and Applications addresses a critical knowledge gap in the field of superamphiphobic surfaces, a class of materials with the extraordinary ability to repel water, oil, and other liquids, by both exploring their fundamentals and also offering detailed insights into their fabrication techniques, characterization methods, and durability considerations. The book presents practical applications of superamphiphobic surfaces in self-cleaning, anti-fouling, environmental clean-up, biomedicine, and food packaging and processing.
The book is divided into five parts. Part I lays the foundation for understanding superamphiphobic surfaces by introducing the fundamental principles that govern their behavior. Part II discusses the fabrication techniques developed to produce superamphiphobic surfaces with varying complexity, durability, and functionality. Part III provides guidelines to evaluate the performance of superamphiphobic surfaces. Part IV highlights several key areas where these surfaces are already being applied. Part V addresses the current challenges and prospects of superamphiphobic surfaces.
Written by an experienced team of researchers, Superamphiphobic Surfaces covers sample topics such as:
- The increased level of sophistication required to achieve superoleophobicity, particularly for liquids with low surface tension
- Contact angle hysteresis, wetting regimes, and the role of micro- and nanoscale structures in achieving extreme liquid repellency
- Specific challenges associated with scaling up fabrication techniques in industrial applications
- Performance criteria including mechanical durability, resistance to liquid impalement, and self-healing capabilities
- The lifespan of various materials in harsh environments such as oil rigs, pipelines, and marine vessels
Empowering readers with knowledge to drive innovation, solve practical problems, and enhance their expertise, Superamphiphobic Surfaces is an essential reference for researchers and professionals in materials science, healthcare, environmental protection, and other fields.
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Table of Contents
Cover
Table of Contents
Title Page
Copyright
Preface
About the Editors
Part I: Fundamentals
Chapter 1: Fundamental Understandings of Superamphiphobicity
1.1 Natural Creatures with Special Wettability
1.2 Characterization of Wettability
1.3 The Mechanism for Superamphiphobicity
1.4 Summary and Outlook
Acknowledgments
References
Chapter 2: Mechanical Durability of Superamphiphobic Surfaces: Fundamentals
2.1 Introduction
2.2 Theory of Wetting
2.3 Mechanical Durability Influenced by Key Parameters
2.4 Common Characterization Methods for Mechanical Durability
2.5 Strategies to Improve Mechanical Durability
2.6 Summary and Outlook
References
Part II: Fabrication
Chapter 3: Advanced Techniques for Fabrication of Superamphiphobic Surfaces
3.1 Introduction
3.2 Fabrication Methods
3.3 Conclusion
Acknowledgments
References
Chapter 4: Superamphiphobic Polymeric Surfaces: Progress and Advances in Fabrication Methods
4.1 Introduction
4.2 The Fabrication of Superamphiphobic Polymeric Surfaces
4.3 Conclusion and Perspectives
References
Chapter 5: Superamphiphobic Surfaces Based on Natural Nanomaterials
5.1 Introduction
5.2 Superamphiphobic Surfaces Based on Natural Clay Minerals
5.3 Superamphiphobic Surfaces Based on Natural Polymeric Nanomaterials
5.4 Superamphiphobic Surfaces Based on Other Natural Materials
5.5 Advantages and Challenges
5.6 Prospects and Outlook
References
Chapter 6: Superamphiphobic Fabrics
6.1 Introduction
6.2 Design Principles of Superamphiphobic Fabrics
6.3 Fabrication Methods of Superamphiphobic Fabrics
6.4 Testing of Superamphiphobic Fabrics
6.5 Functional Applications of Superamphiphobic Fabrics
6.6 Challenges and Perspectives
References
Chapter 7: Superamphiphobic Surfaces by Electrochemical Processes
7.1 Introduction
7.2 Chemical Etching
7.3 Anodizing
7.4 Electrodeposition
7.5 Conclusion
References
Part III: Performances
Chapter 8: Mechanically Durable Superamphiphobic Surfaces
8.1 Introduction
8.2 Enhancement Strategies of Superamphiphobic Surface
8.3 Conclusion and Future Perspectives
References
Chapter 9: Impalement-resistant Superamphiphobic Surfaces
9.1 Introduction
9.2 Impalement-resistant Superamphiphobic Surfaces
9.3 Applications of Impalement-resistant Superamphiphobic Surfaces
9.4 Conclusion and Perspectives
References
Chapter 10: Self-healing Superamphiphobic Surfaces
10.1 Introduction
10.2 Self-healing Methods and Mechanisms
10.3 Conclusion and Outlooks
Acknowledgments
Conflict of Interest
References
Part IV: Applicationsications
Chapter 11: Superamphiphobic Surfaces for Anti-icing and De-icing
11.1 Static and Dynamic Wetting on Superamphiphobic Surfaces
11.2 Icing and Frosting Phenomena on Solid Surfaces
11.3 Ice Adhesion on Superamphiphobic Surfaces
11.4 Concluding Remarks
References
Chapter 12: Superamphiphobic Surfaces for Self-cleaning and Antifouling
12.1 Introduction
12.2 Superamphiphobic Surfaces for Antifouling
12.3 Superamphiphobic Surfaces for Self-cleaning
12.4 Current Status and Future Research Directions
References
Chapter 13: Superamphiphobic Surfaces for Corrosion Protection
13.1 Introduction
13.2 Applications of Superamphiphobic Surfaces in Corrosion Protection
13.3 Conclusion and Outlook
References
Chapter 14: Superamphiphobic Surfaces for the Sustained Maintenance of Building Materials
14.1 Building Materials Degradation
14.2 Superamphiphobic Surfaces for Building Materials
14.3 Key Bottlenecks and Improvement Strategies
14.4 Conclusion and Perspective
Acknowledgments
References
Part V: Challenges and Prospects
Chapter 15: Current Challenges and Prospects in Superamphiphobic Surfaces Technology
15.1 Introduction
15.2 Main Challenges of Current SAP Materials
15.3 Future Prospects
15.4 Conclusion
Author Contributions
Acknowledgments
References
Index
End User License Agreement
List of Illustrations
Chapter 1
Figure 1.1 Habitus images and respective morphological characteristics of repre...
Figure 1.2 (a) Rough structures can enhance surface wettability. (b) The droplet...
Figure 1.3 Chemical structures of commonly used perfluorinated materials applie...
Figure 1.4 (a) SEM image of the hierarchically structured surface illustrating ...
Figure 1.5 (a) Schematic depicting the impact of various reentrant topography fo...
Figure 1.6 (a) Schematic illustration of the process for F-MWCNTs coating prepar...
Chapter 2
Figure 2.1 Schematic diagram of contact angles formed between the liquid and so...
Figure 2.2 Different wetting models. (a) Young model, (b) Wenzel model, and (c)...
Figure 2.3 The surface morphology of materials (before and after abrasion) and ...
Figure 2.4 The relationship between sliding distance and CAs of (a) water and (...
Figure 2.5 (a) Pictures of the SPET/FD-POS@SiO
2
coating different dro...
Figure 2.6 The static CAs of superamphiphobic coating on the magnesium alloys af...
Figure 2.7 (a) The scheme of nanoscratching experiment [35] / with permission o...
Figure 2.8 (a) The scheme of abrasion test on the superamphiphobic surface [37]...
Figure 2.9 The schematic of (a) sand drop impact device [42] / with permission ...
Figure 2.10 The change of CA and SA of (a) coated polyethylene terephthalate fab...
Figure 2.11 The illustration of the tape stripping test [42] / with permission o...
Figure 2.12 (a) Schematic diagram of the constitution of the micro/nano reentran...
Figure 2.13 The schematic illustration of the fabrication process of superamphip...
Figure 2.14 (a) The forming mechanism of polyvinylidene fluoride/cationic fluoro...
Figure 2.15 (a) A UV curable self-healing superamphiphobic coatings [56] / with ...
Chapter 3
Figure 3.1 SEM micrographs and WCAs of 3.5% NaCl (left) and
n
-hexadecane (right;...
Figure 3.2 (a–f) A microtopography of the fabricated superamphiphobic RPSC coat...
Figure 3.3 Schematics of the fabrication procedures for (a) FAS@SFM and (b) FAS...
Figure 3.4 (a) Schematic represents the fabrication process of superamphiphobic...
Figure 3.5 (a) A fabrication procedure of the superamphophobic micropillar arra...
Figure 3.6 (a) Schematic depicts the fabrication of 1PP:9PTFE Cu, schematic dia...
Figure 3.7 (a) Schematic diagram of the coating on an aluminum surface with PFO...
Figure 3.8 (a) Schematic of the preparation process of the superamphiphobic sil...
Figure 3.9 (a) Schematic illustration of synthesis route of HS-SH-F and (b) HS-S...
Figure 3.10 (a) Procedure for the coating treatment and crosslinking structure o...
Figure 3.11 (a) Illustration of the fabrication process for the superamphiphobic...
Figure 3.12 (a) Schematic illustration of the synthesis of the non-wetting surfa...
Chapter 4
Figure 4.1 Schematic representation of three strategies for the fabrication of ...
Figure 4.2 (a) SEM image of a hierarchically structured surface illustrating the...
Figure 4.3 (a) Backside 3D diffuser lithography’s schematic diagram. (b–d) Fabr...
Figure 4.4 (a) Steps for fabrication of nanoparticle-decorated micropillars for...
Figure 4.5 (a) Optimized fluorocarbon-coated oxygen plasma superamphiphobic sur...
Figure 4.6 SEM images of perfluorosilane-treated PEEK (right) and PMMA (left) s...
Figure 4.7 SEM images PEDOT-NH-F
4
, PEDOT-NH-F
6
, and PEDOT-...
Figure 4.8 (a) Sequential development of superamphiphobic and superhydrophobic ...
Figure 4.9 (a) Chemical structure of PIPSMA-
b
-PFOEMA. (b) Processes and a few s...
Figure 4.10 (a) PDMS replica preparation of a Colocasia leaf (PDMS replica). (b)...
Figure 4.11 SEM images of (a) pristine PET fabric, (b) pristine PET fiber, (c) S...
Chapter 5
Figure 5.1 (a) Preparation of palygorskite@fluoroPOS and superamphiphobic palyg...
Figure 5.2 (a) Images of the colorful superamphiphobic coatings prepared using ...
Figure 5.3 Corrosion protection for magnesium alloy by the self-healing superam...
Figure 5.4 The proposed structure of the superamphiphobic coating prepared from...
Figure 5.5 Schematic illustration of synthesis route of fluorinated halloysite ...
Figure 5.6 Schematic illustration of the pH-responsive wettability of the super...
Figure 5.7 The oil-filled precursor capsules made from toluene diisocyanate, na...
Figure 5.8 Preparation and SEM topography of rigid core-shell superamphiphobic ...
Chapter 6
Figure 6.1 Schematic preparation of the FD-POS@PET fabrics through dip-coating ...
Figure 6.2 Fabrication process of superamphiphobic fabric through spraying [50]...
Figure 6.3 Preparation of superhydrophobic fabrics through chemical etching
Figure 6.4 Schematic view of coating where side chains consisting of a tail can...
Figure 6.5 (a) L*, (b) b*, and (c) photographs of the pristine, ink-contaminate...
Figure 6.6 Thermal properties and flame retardant properties of the fabrics
Figure 6.7 Hot liquid repellency of the FD-POS@PET fabric [12] / with permission...
Figure 6.8 Photocatalytic antimicrobial surface property [83] / with permission...
Chapter 7
Figure 7.1 Building-block macroporous structures obtained by immersion of Al sub...
Figure 7.2 Densely packed triangular bayerite (Al(OH)
3
) nanoprisms obtained by ...
Figure 7.3 Cu microstructures obtained by mechanically pressed a Cu substrate w...
Figure 7.4 Porous Al
2
O
3
nanostructures obtained by a two-step anodizing on Al s...
Figure 7.5 Porous Al
2
O
3
nanostructures obtained by anodizing an Al substrate pr...
Figure 7.6 Porous TiO
2
nanostructures obtained by anodizing a microstructured T...
Figure 7.7 Mg(OH
2
) nanoribbons obtained by anodizing a microstructured Mg subst...
Figure 7.8 Flower-like Cu
2
O structures obtained by electrodeposition in copper ...
Figure 7.9 Pyramidal Ni/Cu structures obtained by electrodeposition on Cu nanoc...
Figure 7.10 ZnO reentrant structures obtained by electrodeposition on colloidal ...
Figure 7.11 Densely packed needle-like structures obtained by electrodeposition ...
Figure 7.12 Microstructures and nanoporosities obtained by electrodeposition in ...
Figure 7.13 Nanofibers obtained by electrodeposition in EDOT substituted with pe...
Figure 7.14 Electrodeposition on stainless steel meshes in three different monom...
Figure 7.15 Different morphologies obtained by electrodeposition using the
ante
...
Figure 7.16 Variation of water and diiodomethane droplets by electro-copolymeriz...
Chapter 8
Figure 8.1 Wetting states of an oil droplet on different surfaces in the air. (a...
Figure 8.2 Organic binder reinforcement superamphiphobic surface [33] / with per...
Figure 8.3 Inorganic binder reinforcement superamphiphobic surface [15] / with p...
Figure 8.4 Self-similar structure superamphiphobic materials [18] / with permis...
Figure 8.5 Self-similar structure superamphiphobic surface [24] / with permissio...
Figure 8.6 Nanopore-embedded microtexture superamphiphobic surface [1] / with p...
Figure 8.7 Framework structure of a superamphiphobic surface [18] / Springer Nat...
Figure 8.8 Scratch self-healing superamphiphobic surface [30] / with permission...
Figure 8.9 Structure self-healing superamphiphobic surface [21] / John Wiley & ...
Figure 8.10 Flexibility and abrasion tolerance superamphiphobic surface [25, 26]...
Chapter 9
Figure 9.1 Liquid repellency of double re-entrant PDMS microfibrils. (a) Schemat...
Figure 9.2 (a) Schematic illustration of controllable structure parameters in t...
Figure 9.3 (a–d) TEM image, SEM image, and schematic illustration of the supera...
Figure 9.4 (a–d) SEM images of the superamphiphobic surfaces of ridge structure...
Figure 9.5 (a, b) CAs and SAs of various liquid droplets with their temperature...
Figure 9.6 (a–c) Schematic illustration of fabrication superamphiphobic surface...
Figure 9.7 Schematic illustration of the difference in anticorrosion performanc...
Figure 9.8 (a) Freezing time and (b–d) freezing process of water droplets on th...
Chapter 10
Figure 10.1 (a) Photos to show droplets of water, olive oil, and hexadecane on t...
Figure 10.2 The photothermal self-healing process [24] / with permission of Else...
Figure 10.3 Schematic diagram of the releasable particle-capsules strengthened s...
Figure 10.4 Schematic diagram of the fabrication of multifunctional superamphiph...
Figure 10.5 Schematic illustration of self-healing and anticorrosion mechanisms ...
Figure 10.6 Schematic illustration of the superamphiphobicity, self-healing, and...
Figure 10.7 Preparation and self-healing mechanism of the superamphiphobic coati...
Chapter 11
Figure 11.1 Sketch of a sessile droplet sitting on an ideal solid surface (a), a...
Figure 11.2 (a) A water droplet slides down an inclined hydrophobic surface. (b,...
Figure 11.3 Impact and rebound of a water droplet on a superhydrophobic surface....
Figure 11.4 Variation of the restitution coefficient with the impact Weber numbe...
Figure 11.5 (a) Temporal variation of droplet temperature during the freezing pr...
Figure 11.6 (a) Dependence of the
f
′ factor on the surface wettability (θ)...
Figure 11.7 Schematic diagram of the full process of condensation frosting [58] ...
Figure 11.8 Sketch of the shear test (a), centrifugal force test (b), and tensil...
Figure 11.9 (a) Sketch of water on superhydrophobic surfaces in the Cassie state...
Chapter 12
Figure 12.1 Comparison of the adverse effects of (a) biofouling attached to the ...
Figure 12.2 Corrosion protection by ordinary concrete (O-concrete) compared to a...
Figure 12.3 (a) Schematic of a separation mesh with (b) configuration of oil/wat...
Figure 12.4 Effect of surface modification with PDMS on antifouling property of ...
Figure 12.5 Variations in the output voltages of solar cells with pristine/modif...
Figure 12.6 Evolution of water/oil droplets on surfaces of pristine and self-cle...
Chapter 13
Figure 13.1 (a) Optical photographs of the wettability of the EP/PF-POS@SiO
2
coa...
Figure 13.2 (a) Schematic fabrication diagram of the hierarchically structured s...
Figure 13.3 (a) Schematic fabrication diagram and self-healing process of supera...
Figure 13.4 (a) Water droplets (blue) and oil droplets (red) on a superamphiphob...
Figure 13.5 (a) Optical photograph of the Lecce stone substrate with self-cleani...
Figure 13.6 (a) Schematic preparation diagram of the superamphiphobic wood. (b) ...
Figure 13.7 (a) Schematic fabrication diagram of the FD-POS@PET fabric. (b) Opti...
Figure 13.8 (a) Schematic fabrication diagram of the SFC and optical photographs...
Figure 13.9 (a) Schematic fabrication diagram of the superamphiphobic fabric. (b...
Figure 13.10 (a) Schematic fabrication diagram of superamphiphobic coatings. (b) ...
Figure 13.11 (a) Schematic fabrication diagram of superamphiphobic surface on bam...
Chapter 14
Figure 14.1 The typical degradation patterns of building materials in outdoor en...
Figure 14.2 Schematic representation of multifunctional superamphiphobic protect...
Figure 14.3 The specific requirements for eligible protective coatings for histo...
Figure 14.4 (a) Superamphiphobic coatings prepared on marble and sandstone sampl...
Figure 14.5 SEM images of Lecce stone (a) and sandstone (b) treated with Si-PFE,...
Figure 14.6 (a) The superamphiphobic coatings with strong black and (b) white co...
Figure 14.7 (a) Surface adhesion of
S. aureus
and
S. aureus pbp4
before and afte...
Figure 14.8 (a) Schematic illustration of the fabricated reentrant-coordinated s...
Figure 14.9 (a) Schematics of the nanosphere template-assisted spray coating met...
Figure 14.10 (a) Schematic illustration of the superamphiphobic fabric deposited ...
Chapter 15
Figure 15.1 Factors that affect the wettability of SAP surfaces. (a) Phases and ...
Figure 15.2 The circulation of PFCs in the ecosystem.
Figure 15.3 Routes of PFCs entering into the human body and the side effects on ...
Figure 15.4 Mechanical impacts and their consequences on SAP surface structures ...
Figure 15.5 Illustrations of chemical etching on SAP surfaces. (a) Aqueous dropl...
Figure 15.6 Other limitations that hinder the application of SAP surfaces. (a) T...
Figure 15.7 The utilization of advancing technologies in the theory, preparation...
Figure 15.8 Envisioned production of SAP surfaces based on green chemistry. Sira...
Figure 15.9 Utilization of sensors for defect detection on SAP surfaces and thei...
Figure 15.10 Future applications of SAP surfaces in various fields. Real Vector /...
List of Tables
Chapter 11
Table 11.1 Representative theoretical models for the maximum spreading factor β...
Table 11.2 Total freezing delay time on micro-, nano-, and micro/nano-hierarchi...
Table 11.3 Adhesion strength on micro-, nano-, and micro/nano-hierarchical stru...
Table 11.4 Adhesion strength of ice measured on superhydrophobic surfaces in th...
Chapter 13
Table 13.1 A simple comparison of different superwetting surfaces.
Chapter 15
Table 15.1 Elimination half-life of various PFCs in different species.
Table 15.2 Current technologies for preparing SAP surfaces.
Guide
Cover
Table of Contents
Title Page
Copyright
Preface
About the Editors
Begin Reading
Index
End User License Agreement
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Superamphiphobic Surfaces
Fabrication, Characterization, and Applications
Edited by Junping Zhang and Mohammad Shahid
Editors
Prof. Junping Zhang
Lanzhou Institute of Chemical Physics
Chinese Academy of Sciences
Lanzhou, 730000
China
Dr. Mohammad Shahid
Koneru Lakshmaiah Education Foundation
Vaddeswaram, 522502
India
Cover Design: Wiley
Cover Image: © Junping Zhang
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Preface
The ever-growing demand for advanced materials with exceptional functionalities has led to significant research in surface science. Among the most innovative developments in this field are superamphiphobic surfaces. These surfaces, which repel both water (superhydrophobicity) and oils (superoleophobicity), have emerged as game changers across various industries due to their ability to resist wetting by a wide range of liquids. Superamphiphobic surfaces find applications in numerous fields, including textiles, electronics, construction, and environmental protection, offering solutions to challenges like contamination, corrosion, and biofouling. The potential for these surfaces to revolutionize everyday materials is vast, with implications for everything from self-cleaning technologies to enhanced safety in harsh environments. This book, Superamphiphobic Surfaces: Fabrication, Characterization, and Applications, aims to provide an in-depth exploration of the science, engineering, and practical applications of superamphiphobic surfaces. By presenting a comprehensive overview of recent advances in both the theoretical and applied aspects of these surfaces, this book is a valuable resource for researchers, engineers, and professionals seeking to leverage the benefits of superamphiphobic surfaces for industrial and scientific applications. The structure of this book is carefully organized into five parts, each addressing different facets of superamphiphobic surfaces – from their fundamental principles and fabrication techniques to their performance characteristics, real-world applications, and the challenges and prospects of superamphiphobic surfaces.
The first part of this book lays the foundation for understanding superamphiphobic surfaces by introducing the fundamental principles that govern their behavior. It is essential to comprehend the intricate interplay between surface chemistry and surface texture to design surfaces that repel water and oils. Superamphiphobicity is achieved through a delicate balance of surface energy and roughness. While superhydrophobic surfaces are relatively well understood and have been the focus of substantial research, achieving superoleophobicity – particularly for low surface tension liquids – requires more sophisticated design and engineering. This section covers the basics of surface wettability and the underlying mechanisms that give rise to superamphiphobic properties. Readers are introduced to concepts such as contact angle hysteresis, wetting regimes, and the role of micro- and nanoscale structures in achieving extreme liquid repellency. Theoretical models that explain the behavior of superamphiphobic surfaces are also discussed, providing a scientific framework for understanding how these surfaces function. By understanding the fundamentals, readers will be better equipped to appreciate the advanced fabrication methods and performance evaluations presented in later sections.
The second part discusses the fabrication techniques developed to produce superamphiphobic surfaces with varying complexity, durability, and functionality. Creating superamphiphobic surfaces involves carefully engineering the surface roughness and chemistry to achieve the desired wetting behavior. This section presents various advanced fabrication methods, ranging from simple chemical treatments to sophisticated techniques like electrochemical deposition, plasma etching, and nanomaterials. Readers are introduced to the latest developments in the fabrication of superamphiphobic surfaces, including polymeric materials, natural nanomaterials, and hybrid composites. In addition to discussing the materials and methods used to fabricate these surfaces, this section also covers the specific challenges associated with scaling up these techniques for industrial applications. For example, researchers are actively addressing the critical challenge of creating durable and mechanically robust superamphiphobic surfaces that can withstand real-world conditions without losing their functionality. By exploring the various fabrication strategies available, this section provides readers with a toolkit for designing and producing superamphiphobic surfaces tailored to specific applications.
In the third part, the focus shifts to evaluating the performance of superamphiphobic surfaces. A key challenge in developing these surfaces is maintaining their functionality under mechanical wear, chemical exposure, and environmental stress. While many laboratory-prepared surfaces exhibit impressive superamphiphobic properties in controlled settings, their durability and performance in practical applications often fall short. This section examines various performance criteria for superamphiphobic surfaces, including mechanical durability, resistance to liquid impalement, and self-healing capabilities. Durability is crucial for applications in textiles, construction, and marine environments, where surfaces are exposed to abrasive forces and contaminants. The impalement resistance of superamphiphobic surfaces is another important performance metric, particularly for applications in extreme environments where high-pressure fluids could penetrate the surface’s protective layer. Self-healing surfaces, which can restore their superamphiphobic properties after damage, are also explored as an innovative solution to the problem of surface degradation over time. By examining these performance aspects in detail, this section provides insights into how superamphiphobic surfaces can be optimized for different applications, ensuring that they deliver consistent and reliable performance in various settings.
The fourth part highlights several key areas where these surfaces are being applied, focusing on anti-icing, self-cleaning, antifouling, and corrosion protection technologies. These applications demonstrate the versatility of superamphiphobic surfaces in solving real-world problems, from reducing the need for de-icing chemicals on aircraft to preventing biofouling in marine environments. The anti-icing properties of superamphiphobic surfaces are particularly interesting for industries like aviation and transportation, where ice accumulation poses significant safety risks. In self-cleaning and anti-fouling applications, superamphiphobic surfaces can reduce the need for harsh cleaning agents, leading to more sustainable and environmentally friendly solutions. In corrosion protection, these surfaces provide a barrier against moisture and chemicals, extending the lifespan of materials in harsh environments such as oil rigs, pipelines, and marine vessels. The potential of superamphiphobic surfaces for protecting building materials, emphasizing their self-cleaning properties and ability to resist environmental degradation, has also been discussed. By presenting examples of superamphiphobic surfaces in action, this section demonstrates the real-world impact of this technology and its potential to drive innovation across multiple industries.
The final part of this book addresses the current challenges and prospects of superamphiphobic surfaces. While significant progress has been made in understanding and fabricating these surfaces, there are still many obstacles to overcome before they can be widely adopted. Challenges such as long-term durability, cost-effective production, and scalability must be addressed to bring superamphiphobic surfaces to market.
In conclusion, this book provides a comprehensive overview of this rapidly evolving field. By covering the fundamentals, fabrication methods, performance evaluation, applications, and prospects, this book equips readers with the knowledge and tools needed to advance superamphiphobic surface technology.
Editors
Junping Zhang
Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, China
Mohammad Shahid
Koneru Lakshmaiah Education Foundation, India
About the Editors
Junping Zhang obtained his PhD in physical chemistry in 2008 at the Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences (CAS), where he studied silicate-based hydrogels. Between 2009 and 2012, he did postdoctoral studies on superhydrophobic and superamphiphobic coatings with Prof. Stefan Seeger at the Department of Chemistry, University of Zurich, Switzerland. In August 2012, he was appointed as a professor of physical chemistry at LICP, financed by the “Top Hundred Talents” program of CAS. His research interests include the preparation and applications of functional coatings and 3D porous materials with superwettability based on silanes and silicates. He has published over 170 papers with 13 000+ citations and an h-index of 66 in the fields.
Mohammad Shahid, PhD, is an Assistant Professor in the Department of Chemistry, Koneru Lakshmaiah Education Foundation, India. Before joining KLEF, he worked at various esteemed institutions, including Jamia Millia Islamia, New Delhi; Soochow University, China; University of Glasgow, UK; and the Institute of Chemical Technology, Mumbai. Dr. Shahid has received several esteemed fellowships to support his research pursuits, including grants from UGC, India, China Postdoctoral Fellowship, EU Marie Curie Fellowship, and Dr. D. S. Kothari Fellowship. He has contributed to over 50 scientific publications with 4000 citations and h-index of 24. In addition, has also edited and authored several books with renowned international publishing houses.
Part IFundamentals
Chapter 1Fundamental Understandings of Superamphiphobicity
Hui Liu1, Qing Xu1, Chengyuan Zhang1, Jianying Huang2, and Yuekun Lai2,3*
1National & Local Joint Engineering Research Center of Technical Fiber Composites for Safety and Health, School of Textile & Clothing, Nantong University, Nantong 226019, People’s Republic of China
2National Engineering Research Center of Chemical Fertilizer Catalyst (NERC-CFC), College of Chemical Engineering, Fuzhou 350116, People’s Republic of China
3Qingyuan Innovation Laboratory, Quanzhou 362801, People’s Republic of China
*Corresponding author: [email protected]
1.1 Natural Creatures with Special Wettability
In order to acclimatize themselves to the natural environment, many plants and animals in nature have developed particular morphology and structures during long-time evolution. Recent advances in comprehending the underlying mechanisms of naturally occurring superhydrophobic and superoleophobic surfaces have prompted an abundance of biomimetic studies modeled after the characteristics of gecko setae, butterfly wings, and other structures [1, 2]. Particular attention has been paid to a number of well-known instances of oil-repellent surfaces found in nature (in the air) [3]. For example, bacterial (Bacillus subtilis) biofilm colonies and pellicles (Figure 1.1a) have a persistent antiwetting property to many liquids with low surface tension, as reported by Nishimoto et al. [4]. According to Gorb’s group, leafhoppers with consistent and dense coatings of bronchosomes, a type of highly organized particle, were oil-repellent on their integuments (Figure 1.1b) [5]. Werner et al. discovered that springtails (also known as collembolan), as one of the most significant and attractive natural organisms with oil repellency, can sustain themselves without suffocating in water or even oil environments [6–9]. The cuticle structures of these organisms display robust surface plastrons that are made up of hexagonal or rhombic comb-like patterns or secondary granules with hexagonal basic patterns. A visible layer of protective air cushion, characteristic of a superamphiphobic surface, was present on the surfaces after the springtails were submerged in water and oil. After conducting a thorough investigation into the cuticle micro- or nanomorphology of approximately 40 different springtail species (Figure 1.1c–f), the researchers concluded that the extreme oil repellency of these springtails in air is a result of a combination of multiscale roughness (e.g. the reentrant topography) and chemical composition (e.g. chitin or protein). The inspiration from these oleophobic surfaces in nature has paved the way for more examples of oil-repellent surfaces [10–12].
Figure 1.1 Habitus images and respective morphological characteristics of representative oil-repellent examples in nature. (a, a1) Bacterial biofilms of Bacillus subtilis [4] / National Academy of Sciences. (b, b1) Leafhoppers [5] / Royal Society Publishing. (c–f) Different species of springtails [8] / Springer Nature.
1.2 Characterization of Wettability
A sessile drop will normally form in the shape of a sphere sectioned by the surface when it is placed on a flat substrate. There is a discrete and measurable contact angle between the sphere and the surface at the circular solid–liquid–vapor three-phase contact line. Generally speaking, a hydrophilic surface possesses , while hydrophobicity displays . A surface is specifically designated as super-repellent if its is greater than 150° and its sliding angle is less than 10°. Superhydrophobicity refers to a surface that exclusively repels water, while superamphiphobicity is the ability of a surface to exhibit super-antiwetting properties toward both water and other oil liquids with surface energy lower than water. Characterization is crucial in order to explore the superamphiphobic characteristics. The most straightforward method for locating a super-antiwetting surface is usually eye visualization. Using this technique, the wetting and flowing behaviors can be observed when a probing liquid is applied gently to the surface. If oils and water can both flow across the surface easily, it is considered superamphiphobic. However, precise professional equipment is required to measure the static contact angle and contact angle hysteresis in order to accurately distinguish between various super-repellent properties.
1.2.1 Static Contact Angle
Classically, the static contact angle, as given by Young’s equation (Figure 1.2a), is the traditional method used to determine the surface wettability. When a droplet of fluid comes into contact with a surface, a combination of interfacial tensions between the solid–liquid , solid–vapor and liquid–vapor interfaces can control the contact angle:
Figure 1.2 (a) Rough structures can enhance surface wettability. (b) The droplet with high adhesive force in the Wenzel state can firmly adhere to the substrate surface even when it is reversed downwards. The droplet with low adhesive force in Cassie state can easily roll down the substrate. (c) Several typical states of super-repellant surfaces: “petal” state; “gecko” state; metastable Cassie state; and liquid-infused state [25]. Schematic illustration of the characterization analysis for contact angle hysteresis [26]: (d) advancing and receding contact angle ; tilt angle, i.e. the so-called roll-off angle or sliding angle (e) and the shedding angle (f).
However, the aforementioned Young’s equation [13] only can be applied to smooth, flat surfaces, ignoring the actual interactions between droplets and substrates as well as other external forces in practical situations [14]. But in fact, such an ideal surface does not exist. Due to the more complex solid–liquid interactions, contact angles on a rough surface typically exhibit fluctuation. Two distinct models have been constructed to represent the water contact in the Cassie–Baxter regime [15] and the Wenzel regime [16] in order to better explain this phenomenon. In the Wenzel regime, surface roughness can promote both wettability and nonwettability, depending on the surface’s chemical properties (Figure 1.2a,b). In this regime, the following equation [17] describes the relationship between the measured and the “true” contact angle of a flat surface :
where is the ratio of the actual surface area of the rough surface to the apparent area.
A composite liquid–vapor–solid interface and a more antiwetting surface might result from stable air pockets existing in rough interstices between the droplets and surfaces. This situation is known as the Cassie–Baxter regime [17].
where is the fraction of the surface that is in contact with the liquid. In this condition, the liquid just partially rests on the surface, with a relatively tiny contact area. Because of the trapped air in the pores, the contact angles of a rough surface composed of the same materials are always significantly larger than those of a flat surface. Consequently, surface morphology plays a very key role in wettability.
The two states described above are always considered as extreme cases where droplets are positioned on extremely repellent surfaces. However, in certain exceptional circumstances, certain intermediate states, such as the “petal” state [18], “gecko” state [19], and metastable Cassie state [20], also occur, where droplets may partially moisten the roughened surfaces (Figure 1.2c). The droplet partially wets the surface of a rose petal as it penetrates into the rough structure. The large-scale micropapillae on the petal surface are shown to be impregnated by droplets, but the nanofolds that sit on top of them remain unwetted. Even when the petals are positioned upside down in this wetting case, the droplets are still able to adhere firmly to their surfaces. Additionally, a different high-adhesion wetting condition known as the “gecko” state explains a negative pressure created by sealed air pockets trapped in the nanospace between the surface and the water droplet, which results in a high adhesive force. As implied by its name, the metastable Cassie state is not an actual equilibrium state. Such a state originates from a superoleophobic surface with local curvature. Despite having low surface tension and liquid CA greater than 90°, the textured surface’s air–liquid interface is pinned by the local surface curvature, which keeps the liquid from penetrating and giving rise to the superoleophobic property [21–24]. Nevertheless, the surface may lose its superoleophobicity if some external disturbance causes it to transition from the metastable Cassie state to the Wenzel state.
It is noteworthy that the liquid-infused surface has been recently developed into a liquid-repelling one. Its repellency, however, cannot be explained by the Wenzel and Cassie–Baxter equations. Rather, instead of using micro/nanoscale features to reject fluids, the liquid-infused surface has eliminated adhesion between the droplet and the substrate depending on the liquid surface. The oil liquids with extremely low surface energy can produce a stable and smooth interface, restricting most liquids from permeating and at the same time resisting the adhesion of a variety of matters [25].
1.2.2 Contact Angle Hysteresis
Not only must the contact angle for water and oil droplets be greater than 150°, but a comparable low contact angle hysteresis (CAH) is also necessary for a super-repellent surface. The difference between two contact angles, viz. advancing contact angle (Adv) and the receding contact angle (Rec) on a surface with a specific roughness or uneven chemical composition is known as the CAH [14]. CAH has an impact on surface adhesion. For example, a self-cleaning surface requires a low hysteresis. Thus, for superhydrophobic and superoleophobic surfaces, CAH is yet another crucial character. Many methods have been devised to date for the characterization of the CAH; the most commonly used ones are and the tilt angle.
Advancing/receding contact angle: Usually, the advancing contact angle and the receding contact angle are typically measured using commercial equipment equipped with an enhanced video microscopy system and digital image analysis (Figure 1.2d). First, a syringe pump is applied to generate a standard water droplet. And then the water fluid is continuously pumped into (or sucked from) the droplet at a lower speed. In the meantime, a solid state charge-coupled device camera displays in a frame grabber. Following the water pumping, the suction action is carried out to recede the water droplet, and to record the [27].
Tilt angle: A critical angle between the substrate and the horizontal surface is termed as the tilt angle, below which the droplet starts to move upon inclining the substrate. For both water and oil droplets, a tilt angle smaller than 10° is thought to be required for the super-repellent surfaces and self-cleaning properties. The two types of tilt angles that are typically distinguished are the sliding angle (; Figure 1.2e) and the shedding angle (; Figure 1.2f). When a droplet fully rolls off the surface due to gravity alone, the angle of inclination of the surface is known as the sliding angle, also known as the roll-off angle. The sliding angle can be measured by the measuring instrument through the use of a tilt plate with an angle that can be adjusted between 0° and 90°. The plate rotates continuously from 0° to 90° during the measuring procedure until the droplet begins to roll or slide off the substrate surface [22, 28]. The rotation angle is immediately noted as. There is, in fact, a small difference between sliding and rolling with respect to the droplet’s real motion. The sliding case has a somewhat bigger contact area between the droplet and the substrate than the rolling case. Furthermore, in the former case, the droplet gets stuck on the substrate because of the strong adhesive force, whereas in the latter case, the droplet is free to roll [29–31]. Nevertheless, in most of the cases, the difference was not reported along with the recorded angle. The sliding angle approach is no longer suitable when measuring surface adhesion on some difficult surfaces, including textiles, because of the many clinging fibers that obstruct droplet sliding [28]. Consequently, a new method called the shedding angle has been proposed for the characterization of superhydrophobic textiles [32]. In essence, the shedding angle is a critical angle at which a water droplet of a certain volume dropped from a set height begins to roll off or bounce away from the inclined substrate. When comparing data from several studies, caution must be taken because the drop volume and needle-to-substrate distance have an impact on the measured value.
1.3 The Mechanism for Superamphiphobicity
1.3.1 Chemical Composition
Owing to its decisive effect on surface energy, the chemical composition is a major factor in a material’s wettability. Young’s equation (Eq. 1.1) provides a good description of the CA of a flat substrate [13]. On a flat surface, hydrophobicity or oleophobicity must be achieved with a CA greater than 90° for both water and oil droplets. is less than if CA is more than 90°. Ignoring that the contact force between two surfaces has an actual order, Eq. (1.4) allows us to approximate the [33]:
The surface free energy of the solid substrates should be sufficiently low to be less than one-quarter of the surface free energy of the liquid , as determined by combining Eqs. (1.1) and (1.2). Some common oils, including hexadecane, have surface tensions that are typically substantially lower than water’s (27.5 m Nm−1). Therefore, the solid surface’s surface energy needs to be extremely low, just a few m Nm−1, in order to achieve superoleophobicity. Only a few unique chemical groups, such as , allow for this. This rigid requirement restricts the choice of materials and enhances the challenge of fabricating superamphiphobic surfaces.
Generally speaking, the appropriate materials can be created by depositing molecular perfluoroalkane that has a functional group at one terminal (F-monomer), such as 1H,1H,2H,2H-perfluorooctyl phosphate (PFOP), 1H,1H,2H,2H-perfluorooctanoic acid (PFOA), 1H,1H,2H,2H-perfluorooctyl trichlorosilane (PFOTS), 1H,1H,2H,2H-perfluorodecyl trichlorosilane (PFDTS), 1H,1H,2H,2H-perfluorodecane-1-thiol (PFDSH), and 1H,1H,2H,2H-perfluorodecyl acrylate (PFDAE). Additionally, it can also be achieved by spin- or spray-coating a solution of fluorinated polymers (F-polymers). F-monomers can always be grafted to create a fluorinated layer either liquid phase deposition or vapor phase deposition.
The fluorinated materials can be broadly classified into the following groups based on the types of chemical modification materials: fluoroalkane, perfluorocarboxylic acid, fluoropolymers, fluorosurfactants as well as C4F8 plasma. Figure 1.3 summarizes a few perfluorinated compounds that are often utilized. This section will cover the benefits and drawbacks of each fluorinated material.
Figure 1.3 Chemical structures of commonly used perfluorinated materials applied to the surface modification of a roughened substrate.
1.3.1.1 Fluoroalkane
Fluoroalkanes are frequently utilized for prepatterned surfaces and are thought to be the ideal compounds to make superamphiphobic surfaces. Generally, perfluoroalkane with a functional group at the chain terminal (F-monomer) can be deposited on a variety of substrates to generate a fluorinated layer. Fluorosilanes and fluorothiols are the two types of fluroroalkanes that are frequently employed.
Fluorosilanes: On many different patterned substrates, fluorosilanes can produce thin, self-assembling layers. Before fluorination, the patterned surface must be activated (by UV or plasma) to form on the surface. After fluorosilanes are added, a covalently linked layer can be achieved. Fluorosilanes that are primarily used in applications are 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS), 1H,1H,2H,2Hperfluorodecyltrichlorosilane (PFDTS), and 1H,1H,2H,2Hperfluorodecyltriethoxysilane (PFDTES). Wong et al. have fabricated transparent and superamphiphobic surfaces with inverted cone nanostructures by omnidirectional self-assembly of nanoparticle aerosols and gas phase fluoro-silanization of PFOTS [34]. Besides, using a simple molding technique and PFDTS modification, Jang et al. were able to successfully produce functional superamphiphobic polymer-based surfaces [35]. The molding template was composed of hierarchical structures with ratchet-like microscale structures and nanoscale spheres and an ultrathin-protecting layer for the repeated molding process.
Fluorothiols: The fluorothiols are efficient fluoroalkane modifiers to reduce the surface energy of reentrant structure, much like fluorosilane. Moreover, thiols are able to form a thin, self-assembling layer on the substrates. However, they lack oxidative stability and are restricted to specific substrates like copper, silver, gold, platinum, palladium, or palladium [36–38]. 1-Decane-thiol (DT), as one type of fluorine-free low surface tension material, is utilized to passivate the prepatterned surface. The surface energy of DT is higher than that of PFDT (1H,1H,2H,2H) due to the distinct functional groups in their chemical structures (DT possesses , PFDT ) [38]. Using a two-step surface texturing procedure and surface fluorination with PFDT, Ou et al. created a superamphiphobic surface [38]. Superamphiphobicity of the surface could be restored with remodification with PFDT, demonstrating indirectly that PFDT desorption may be the cause of the deterioration.
1.3.1.2 Perfluorocarboxylic Acids
Perfluorocarboxylic acid has also been employed to reduce the reentrant structure’s surface energy. It is often applied to the prepatterned surface, just like the fluoroalkane compounds. Perfluorooctanoic acid (PFOA) [39], perfluorononanoic acid (PFNA) [40], and perfluorodecanoic acid (PFDA) [41] are examples of perfluorocarboxylic acids that are often used. Chen et al. [39] have developed a strong and long-lasting superamphiphobic surface with great repellency to various liquids, including water, glycerol, peanut oil, and some chemical solvents. The superamphiphobic powder’s primary constituents were Cu and Cu2O, which were covered in CF3 and CF2 functional groups. The superamphiphobic surface exhibited a high number of morphologies that resembled leaves, protrusions, and corallines, which randomly aggregated and were covered in a huge number of micro/nanoparticles.
1.3.1.3 Fluoropolymer
Another ideal low surface tension material for fluorinated modification is fluoropolymer. Usually, it mixes with nanoparticles, which are employed to produce superamphiphobicity by raising the surface roughness. The fluoropolymer’s shortcomings include its inability to attain sufficient roughness on its own and its unsuitability for pretextured surfaces. That is to say, more nanoparticles need to be introduced [42]. Furthermore, there is a need for additional improvement in the durability of the fluoropolymer-based superamphiphobic surface. Using SiO2 nanoparticles and fluorinated polyurethane, Wang et al. created a superamphiphobic breathable membrane that was comparable to the process used to make amphiphobic nanofibrous membranes made of poly (trifluoroethyl methacrylate) and electrospun silica [42]. A three-step polymerization process with a terminal perfluoroalkane segment produced the fluorinated polyurethane.
1.3.1.4 Polyhedral Oligomeric Silsesquioxane
POSS, or polyhedral oligomeric silsesquioxane, is an organosilicon molecule that resembles a cage. It is surrounded by either 1H,1H,2H,2H-perfluorodecyl (FD-POSS) or 1H,1H,2H,2H-perfluorooctyl (FO-POSS). POSS has an ultralow surface tension, with a solid surface energy of about 11.5 mN m−1 [43]. Pan et al. [43] created an electrospun layer of fluorodecyl POSS and cross-linked poly(dimethylsiloxane; PDMS) on top of the stainless steel wire meshes. For a variety of various polar and nonpolar low surface tension liquids, such as acids, alkalis, and solvents, the as-fabricated superamphiphobic surface exhibits a high contact angle (Figure 1.4c) due to a hierarchical structure (Figure 1.4a,b) and low surface energy. Crucially, the superamphiphobic surface demonstrates an efficient chemical shielding property and can chemically shield against nearly every type of liquid, whether organic or inorganic, polar or nonpolar, Newtonian or non-Newtonian (Figure 1.4d–f).
Figure 1.4 (a) SEM image of the hierarchically structured surface illustrating the electrospun coating of cross-linked PDMS +50 wt% fluorodecyl POSS on a stainless steel wire mesh 70. (b) SEM image illustrating the reentrant curvature of the electrospun texture. (c) Droplets of various low surface tension liquids showing very high contact angles. Side view of an aluminum plate, immersed in (d1) concentrated hydrochloric acid (HCl) and (d2) concentrated sodium hydroxide (NaOH), respectively. The uncoated aluminum surface reacts violently with HCl or NaOH, releasing bubbles of hydrogen gas, but the coated aluminum surface remains unaffected. The uncoated aluminum surface appears rough and damaged after immersion in (e1) HCl and (e2) NaOH, respectively. The coated aluminum surface remains unaffected after immersion in (f1) HCl or (f2) NaOH, respectively [43] / American Chemical Society; (g) Schematic illustration of the procedure for solution preparation and coating treatment. (h) Illustration of possible interaction among PTFE NPs, FAS, and Zonyl321 [44]; (i,j) Side and top-view SEM images of PDMS mushroom-like micropillar arrays. (k) Transmittance spectra of various samples over UV–Vis wavelength regime. (l) Measurement of static contact angles of the PDMS sample over a time period of 6 months. The insets show optical photographs of various liquids: DI water (transparent), mineral oil (blue), and ethanol (yellow) at different time points [45] / with permission of The Royal Society of Chemistry.
1.3.1.5 Fluorosurfactant
The superamphiphobic surface can also be effectively created using fluorosurfactant with a high surface energy head and a low surface energy tail group [42]. There could be a low surface energy barrier as a result of the fluorinated tails segregating at the surface. Using a wet-chemical technique, Zhou et al. produced a strong, self-healing, and superamphiphobic surface [44], which was created by dispersing fluorocarbon surfactant (DuPont Zonyl321), lyophobic nanoparticles (PTFE NPs), and fluorinated alkyl silane (FAS) in water. The goal of using PTFE NPs was to improve the surface’s mechanical robustness and provide secondary roughness. FAS functioned as a coupling agent to enhance the adherence between the superamphiphobic coating on a variety of substrates, including fabrics, sponges, wood, glass, and metal, while also acting as a low surface tension modifier to lower the surface free energy by introducing a fluorinated alkyl chain (Figure 1.4g,h).
1.3.1.6 Plasma Treatment
Plasma treatment is an additional modifying technique. The octafluorocyclobutane (C4F8) plasma was used in this process to deposit a fluorocarbon film on the substrates. One benefit of the plasma treatment is that, regardless of its morphology, it can be administered to the entire surface [42]. However, due to unique experimental conditions and chemicals that place restrictions on the applications of plasma treatment, it is only applicable to small-scale treatments. Using soft lithographic microfabrication and C4F8 plasma treatment, Kang et al. created a strong superamphiphobic surface with mushroom-shaped micropillars [45]. Reentrant structures were produced using the direct micromolding technique (Figure 1.4i,j). Following the etching procedure, a thin and uniform polymeric layer was formed on the textured surface by introducing the C4F8 gas in a deep reactive ion etch system. In addition, C4F8 gas polymerization provides better resilience and repeatability when compared to alternative surface treatment techniques. Significantly, the polymer structures remain unchanged following the plasma treatment, which is thought to be a beneficial fluorocarbon surface treatment. As a consequence, the superamphiphobic surface is extremely repellent to different liquids with a broad range of surface tensions from 22.3 to 72.1 mN m−1. The superamphiphobic surface has a transmittance of up to 90% (Figure 1.4k) and a durability of at least six months (Figure 1.4l).
1.3.2 Special Rough Morphology
The surface topology is another crucial factor. As previously mentioned, air can become trapped on a rough surface when liquids come into contact, significantly decreasing the contact between the surface and the droplet. However, repelling liquids with extremely low surface tension is not always the case for all rough surfaces with low surface energy. It was far from sufficient for industrial applications to repel just liquids with higher surface energy, such as water and glycol. To construct superoleophobicity, only a certain type of rough structure with reentrant geometries is applicable. In recent years, numerous review articles have concentrated on and gathered information about the design of complicated reentrant geometry, overhang structures, inversetrapezoidal structures, and mushroom-like structures, to fabricate superamphiphobic interfaces, as shown in Figure 1.5a–f [46–50]. The rough structure with reentrant curvature balances the downward mixing force generated by Laplace pressure and droplet gravity and generates an upward combined force, therefore repelling liquids with lower surface tension.
Figure 1.5 (a) Schematic depicting the impact of various reentrant topography for achieving superamphiphobicity. For non-reentrant geometry, the liquid wets the surface for . When for reentrant inverse trapezoidal geometry, the liquid does not wet the surface. But curvature geometry in reentrant structure supports the nonwetting of the surface with . Also, other reentrant geometries support the nonwetting of the surface for and [46] / with permission of Elsevier. (b–f) SEM images of various reentrant geometries that aid in exhibiting superamphiphobicity including [51] / American Association for the Advancement of Science – AAAS (b) electrospun morphology, (c) well-defined micropillar type structures, (d) inverse trapezoidal microarrays, (e) wavy stem with wider head. (f) Overhang T-shaped microstructure [50] / The Royal Society of Chemistry.
1.3.2.1 Reentrant Structure
The notion of the reentrant surface structure was first proposed by Tuteja et al. [51] and used in the construction of superamphiphobic surfaces; it is thought to be an effective technique. Notably, this notion has significantly aided in the advancement of this field. So as to keep low contact angle hysteresis and reasonably high contact angles, superamphiphobic surfaces are predicted to produce composite solid–liquid–air interfaces with air pockets in the valleys between pillars. Reentrant curvature can be produced to some extent via mushroom-shaped structures, micro-hill-like structures, or even randomly stacked nanoparticles [52–55]. As we all know, the concave shape of the top of springtails, as one of the main factors, can contribute to liquid repellency. Kang et al. [52] used silicon microelectromechanical systems and soft lithography techniques to create mushroom-like micropillar (SIMM) arrays that resemble springtails in size and shape, with diminutive heads and broad feet. It was discovered that the meniscus of the SIMM array may be altered to provide selective liquid sliding features by varying the texturing angle and spacing between neighboring microcolumns. This occurs as a result of competition between internal gravity and Laplace pressure near the meniscus. It was shown that the mushroom-like head possesses both superomniphobicity and selective liquid sliding features. Zhang et al. [53] developed superamphiphobic surfaces with micro-hill-like reentrant microstructures by spraying fluorinated multiwalled carbon nanotubes (F-MWCNTs). The F-MWCNTs accumulating randomly and solvent evaporating jointly contributed to this particular reentrant structure. Such surface possesses sliding angles of 1.2° and 4.3° and contact angles of 172.4° and 163.0° for water and cetane, respectively (Figure 1.6a).
Figure 1.6 (a) Schematic illustration of the process for F-MWCNTs coating preparation [53] / with permission of Elsevier. (b) Schematic illustration of liquid-wetting models of a single particle with the radius r wetted by water and hexadecane. (h: penetration depth of the liquids; : the static contact angle of the liquids on a smooth surface possessing identical surface chemistry as the rough surface.) Assumed wetting models for the coating surfaces wetted by water and oil. (c) Schematic illustration of the mechanism of forming the superamphiphobic surface [59] / with permission of Elsevier. (d) General surface SEM, enlarged surface SEM, and cross-section SEM [62] / The Royal Society of Chemistry.
1.3.2.2 Overhang Structure
Previous research [56, 57] has indicated that innately hydrophilic materials can be made to exhibit superhydrophobic behavior if they have surfaces with microtextures with overhanging structures. These features contribute to keep water from entering grooves due to capillary forces. Likewise, it has been shown that superoleophobic surfaces can be formed on innately oleophilic substrates with overhang structures preventing oil from penetrating the textures, thus exhibiting superamphiphobicity [58–60]. Wang et al. [59] have developed a multifunctional coating composed of fluorinated alkyl silane, micro-sized ammonium polyphosphate particles, and functionalized silica nanoparticles (Figure 1.6b,c). A unique randomly overhanging hierarchical structure can be constructed on a variety of surfaces using an easy and economical spaying technique and exhibits super-repellency to water and oils with low surface tensions. Reverse imprint lithography and reactive ion etching techniques were used by Wooh et al. [60] to develop superamphiphobic surfaces with overhang patterns. They also incorporated conical, pillar, hole, and linear nanopatterns onto the overhang structure’s surface in addition to the single overhang structure. The superoleophobicity of embedded holes and linearity could be enhanced by creating a new overhang angle of approximately 0° beside the original overhang structure, while the embedded conical and pillar nanopatterns just decrease the solid–liquid contact area.
1.3.2.3 Porous Structures
Superamphiphobic coatings with porous structures are rarely constructed because of the unclear correlation between the structural parameters of the pores and the repellency of the coating. Nevertheless, it is worth noting that creating air pockets by trapping gas is crucial for liquid repellency as it creates negative Laplace pressure. Liquid repellency is greatly influenced by the amount of air present in the pores or vacancies of porous structures, another important type of nanostructure for creating superamphiphobic surfaces (Figure 1.6d) [61–63]. An artificial porous superamphiphobic surface has been developed by Li et al. [61] by combining adhesive agent polydopamine with hydrophilic SiO2 nanoparticles for constructing a porous micro-network. Following a two-step CVD process, the superhydrophilic microstructure porous coating transformed into a superamphiphobic one. It should be highlighted that a porous coating’s repellency is significantly influenced by structural factors like pore height and size. Therefore, it is advantageous to optimize the structural characteristics in order to improve the coating’s repellency. Besides, Cao et al. [63] have constructed a superamphiphobic, self-cleaning, and robust coatings on a variety of rock substrates depending on the low surface energy of fluorinated compounds and the inherent roughness of stone substrates. The superamphiphobic chemicals are housed in the pores of the stone, which functions as a microstructure to resist abradant removal and maintain the substrate’s chemical and physical integrity.
Generally speaking, the two aforementioned factors should be carefully and extensively considered in order to properly accomplish superamphiphobicity.
1.4 Summary and Outlook
This section briefly introduced the several fundamental wetting states, dimensionless parameters, and design criteria that characterize the performance of a well-defined structured surface. Furthermore, commonly used chemical modification materials and a wide diversity of surface topographies of oil-resistant materials were summarized using pertinent classification.
To fully comprehend the superamphiphobic surface, it is important to discuss both current challenges and promising prospects. Firstly, additional investigation is needed to better comprehend the formation concept of a superamphiphobic system. The fundamental theory plays a very important guiding role in the fabrication and applications of superamphiphobic surfaces. Secondly, in order to quantify the performance stability of the superamphiphobic surface and facilitate performance comparison, a set of predetermined standards should be established. Last but not least, long-chain fluoride, which is frequently employed to reduce surface tension during chemical modification, is poisonous and harmful to the environment. Since low surface energy chemistry is not required, double reentrant structures should be further studied to produce superamphiphobic surfaces, as this is thought to be a more environmentally friendly technique. Double reentrant configurations can be optimized and used to build superamphiphobic surfaces by controlling the structural angle of the structured surface.
Generally speaking, there is still a huge potential for the development of superamphiphobic surfaces. With consistent effort, scientists and engineers will propose more theoretical research based on unique results to further grasp superamphiphobicity. A promising future lies ahead for superamphiphobic surfaces because of their high commercialization value and potential, which is driving an increasing number of scientists and engineers to strive for superamphiphobic surfaces.
Acknowledgments
The authors thank the National Natural Science Foundation of China (52102105, 22075046, 22375047, and 22378068), Natural Science Funds for Distinguished Young Scholars of Fujian Province (2020J06038), Natural Science Foundation of Fujian Province (2022J01568), National Key Research and Development Program of China (2022YFB3804905, 2022YFB3804900, and 2019YFE0111200), and 111 Project (No. D17005).
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