Table Of ContentBio-Inspired
Wettability
Surfaces
© 2016 by Taylor & Francis Group, LLC
© 2016 by Taylor & Francis Group, LLC
Pan Stanford Series on Renewable Energy — Volume 2
Bio-Inspired
Wettability
Surfaces
Developments in Micro-
and Nanostructures
editors
Preben Maegaard
Anna Krenz
Wolfgang Palz
Yongmei Zheng
The Rise of Modern Wind Energy
Wind Power
for the World
© 2016 by Taylor & Francis Group, LLC
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© 2016 by Taylor & Francis Group, LLC
Contents
Preface
1. Lo tus Le af Effect: Micro- and Nanostructures i1x
1. 1 Janus Feature of Lotus Leaf 1
1.1.1 Mechanism of Underwater
Superoleophobicity 4
1.1.2 Other Underwater Superoleophoic
Surface 6
1.2 Fabrication Methods of Underwater
Superoleophobic Surface 8
1.2.1 Template Mimicking 9
1.2.1.1 Mimicking the lotus leaf 9
1.2.1.2 Mimicking micropatterned
surface 11
1.2.2 Surface Coating 15
1.2.3 Assembly 18
1.2.4 Inorganic Materials 21
1.3 Promising Applications 23
1.3.1 Underwater Smart Surface 23
1.3.1.1 Thermal responsive surface 23
1.3.1.2 pH responsive surface 26
1.3.1.3 Electrochemical responsive
surface 30
1.3.2 Oil/Water Separation 32
1.3.3 Anti-Fouling Microfluidic Channel 40
1.3.4 Underwater Oil Capture 41
2. 1B.u4tt erflyC oWnicnlgu sEiffoencst :a nAdn iPsoetrrsoppeicctailvlye Oriented 43
Micro- and Nanostructures 51
2.1 Butterfly Wing 53
2.1.1 SH and Directional Adhesion 53
2.1.2 Anisotropism of Microstructures on
Butterfly Wing Surface 55
2.1.3 Low Temperature Water Repellency 65
© 2016 by Taylor & Francis Group, LLC
vi Contents
2.2 Artificial Surface and Functions 68
2.2.1 Optical Lithography and Interference
Lithography 69
2.2.2 Femtosecond Laser and Etching 72
2.2.3 Embossing, Imprinting and Replica
Molding 74
2.2.4 Wrinkling and Directed Mechanical
Deformation 79
2.2.5 Other Methods 82
2.3 Potential Applications 82
2.3.1 Anisotropic Wetting and
Unidirectional Spreading 84
2.3.2 Adhesion 88
2.3.3 Directional Driving 94
2.3.4 Other Applications 99
3. 2Sp.4id er SOilku tElffooekct : Gradient Micro- and Nanostructures 110101
3.1 Spider Silk 113
3.1.1 Classification of Spider Silk 114
3.1.2 The Influence of Water on the
Mechanical Properties of Spider Silk 121
3.1.3 Directional Water Collection (and
Mechanism) 124
3.1.4 Stronger Capillary Wet Adhesion
(and Mechanism) 138
3.2 Artificial Silk and Functions 145
3.2.1 Dip-Coating Methods 147
3.2.1.1 Method 149
3.2.1.2 Tiny water drops motion 152
3 .1.3 The Research of Three Phase Line 157
3.2.2 Fluid-Coating Method 162
3.2.3 Electrospinning Methods 166
3.3 Promising Applications 170
3.3.1 Control Motion of Liquid Droplet 170
3.3.2 High-Efficiency Water Collection 170
3.3.3 Enhanced Solid–Liquid Adhesion 171
3.3.4 Environmentally Responsive Fiber 171
© 2016 by Taylor & Francis Group, LLC
Contents vii
4. Beetle Back Effect: Heterogeneous Wetting
Micro- and Nanostructure Patterns 177
4.1 Fog Collection (and Mechanism) 177
4.2 Artificial Pattern and Functions 179
4.2.1 Hydrophilic Bumps on (Super)
hydrophobic Wax Films 179
4.2.2 Hydrophilic Bumps on
Polyelectrolyte Multilayers 179
4.2.3 Hydrophilic Bumps on Plasma
Polymers 186
4.2.4 CVD and Photocatalytic
Decomposition 190
4.2.5 Hydrophilic Bumps on Polymer
Films 191
Index4.3 Promises and Applications 194
199
© 2016 by Taylor & Francis Group, LLC
© 2016 by Taylor & Francis Group, LLC
Preface
There has been an exciting confluence of research areas, such as
physics, chemistry, biology and materials science, in recent years. A
kernel consists in organic materials with high/low surface energy, has
various-style micro- and nanostructures, such as regular/irregular,
ordered/disordered, rough/smooth that can be endlessly arranged
and combined, and is greatly provided with adaptability to perfectly
display the biological functions that developed during the thousands
of years evolution in nature. Interestingly, the biological surfaces
develop the micro-/nanostructure with gradient features to smartly
achieve the wetting controls. For example, the ultra-hydrophobic
water repellency on lotus leaf; directional water collection on wetted
spider silk; direction adhesion of super-hydrophobic butterfly wing,
and fog-collecting hydrophobic/hydrophilic pattern on beetle back.
Biological surfaces provide endless inspiration for the design and
fabrication of functional interface materials with unique wettability,
generating promising applications such as micro-fluidic devices,
functional textiles, corrosion resistance, liquid transportation, and
anti-fogging and water-collecting devices.
Researches on wettability, water repellency, bioinspiration, and
biomimetics have shown an increasing trend, and has includeed
realms of materials science, chemistry, physics, engineering, polymer
science, science technology, metal engineering, mechanics, energy
fuels, geology, and so on. On the global front, China has published the
largest number of results in recent years of the researches conducted
and products developed.
The book introduces the recent researches on wettability of
biological and bio-inspired surfaces through its four chapters. The
first chapter focuses on the wettability features and effect in a
lotus leaf. It discusses the basic concept of wettability and suggests
methods for fabrication bio-inspired surfaces and achieving
functional surfaces. In the second chapter, wettability features and
effect in a butterfly wing are described. It specifically stresses on
the anisotropic wettability resulting from anisotropically structured
surfaces. Anisotropy ranges from one dimension to two dimensions
© 2016 by Taylor & Francis Group, LLC
x Preface
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on a surface for droplet movement. Many fabricating methods of bio-
inspired surfaces can be developed further to obtain fluid-controlling
functional surfaces. In the third chapter, the wettability features
and effect of spider silk are introduced and novel mechanisms of
water collection resulting from gradient multi-structures have been
described. Some methods to fabricate bio-inspired materials that
were developed by our team have also been introduced. Finally,
the fourth chapter presents the wettability features and effect of
beetle back for fog collection and discusses about the methods for
fabricating hydrophobic/hydrophilic patterns.
The book offers the mechanisms of smart wetting control, such as
water collection and repellency, on biological micro-/nanostructure
gradient interfaces that were developed by the us in recent years.
It also suggests ideas to mimic biological features to realize bio-
inspired functional surfaces with unique wettability. The book will
help researchers to develop innovatory designs from novel materials
for future scientific works.
© 2016 by Taylor & Francis Group, LLC
