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A review on special wettability textiles: theoretical models, fabrication technologies and multifunctional applications

01 Jan 2017-Journal of Materials Chemistry (The Royal Society of Chemistry)-Vol. 5, Iss: 1, pp 31-55
TL;DR: Inspired by the superhydrophobic lotus surface in nature, special wettability has attracted a lot of interest and attention in both academia and industry as discussed by the authors, and the strategies for constructing fabric surfaces with an anti-wetting property are categorized and discussed based on the morphology of particles coated on the textile fibre.
Abstract: Inspired by the superhydrophobic lotus surface in nature, special wettability has attracted a lot of interest and attention in both academia and industry In this review, theoretical models and fabrication strategies of superhydrophobic textiles have been discussed in detail The strategies for constructing fabric surfaces with an anti-wetting property are categorized and discussed based on the morphology of particles coated on the textile fibre Such special wettability textile surfaces are demonstrated with self-cleaning, oil/water separation, self-healing, UV-blocking, photocatalytic, anti-bacterial, and flame-retardant performances Correspondingly, potential applications have been illustrated for self-cleaning, oil/water separation, asymmetric/anisotropic wetting janus fabric, microfluidic manipulation, and micro-templates for patterning In each section, representative studies are highlighted with emphasis on the special wetting ability and other relevant properties Finally, the difficulties and challenges for practical application were briefly discussed

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A review on special wettability textiles: theoretical
models, fabrication technologies and
multifunctional applications
Shuhui Li,
a
Jianying Huang,
a
Zhong Chen,
b
Guoqiang Chen
a
and Yuekun Lai
*
ac
Inspired by the superhydrophobic lotus surface in nature, special wettability has attracted a lot of interest
and attention in both academia and industry. In this review, theoretical models and fabrication strategies
of superhydrophobic textiles have been discussed in detail. The strategies for constructing fabric
surfaces with an anti-wetting property are categorized and discussed based on the morphology of
particles coated on the textile bre. Such special wettability textile surfaces are demonstrated with self-
cleaning, oil/water separation, self-healing, UV-blocking, photocatalytic, anti-bacterial, and ame-
retardant performances. Correspondingly, potential applications have been illustrated for self-cleaning,
oil/water separation, asymmetric/anisotropic wetting janus fabric, microuidic manipulation, and micro-
templates for patterning. In each section, representative studies are highlighted with emphasis on the
special wetting ability and other relevant properties. Finally, the diculties and challenges for practical
application were briey discussed.
1. Introduction
An extremely high water contact angle of nearly 180
was rst
reported by Ollivier in 1907. Such a super-antiwetting surface
was fabricated via coating a substrate using soot.
1
The
superhydrophobic surfaces with a high static water contact
angle (>150
) and low sliding angle (<10
) had not recei ved
much attention unt il the report of the lotus eect mecha-
nism by Barthlott and Neinhuis in 1997.
2
This unique prop-
erty was attribute d to the combination of a waxy layer with
a low surface energy and a rough structure with protrusions
on lotus leaves (Fig. 1).
3,4
Since then, research in terests on
superhydrophobicity have grown tremendously, with
numerous studies devot ed to mimicking natural plants,
Shuhui Li joined Prof. Lai's
group in College of Textile and
Clothing Engineering at Soo-
chow University to pursue her
Master's degree in 2013. She
continued to pursue her Ph.D.
degree at Soochow University
from 2015. Her current scientic
interests are devoted to fabri-
cating special wettability and
multi-functional textile surfaces
for applying in self-cleaning, oil
water separation, UV shielding
and anti-bacterial materials.
Jianying Huang received her
Ph.D. degree in 2007 from the
Department of Materials, Xia-
men University. During 2007
2011, she worked as an assistant
professor at Fujian Institute of
Research on the Structure of
Matter. Aer that, she moved to
Muenster University as a visiting
scholar. She is currently an
associate professor at National
Engineering Laboratory for
Modern Silk, and School of
Textile and Clothing Engineering in Soochow University since
2013. Her research interests focus on the bio-inspired intelligent
textile surfaces with special wettability, ATRP and click-chemistry
reactions.
a
National Engineering Laboratory for Modern Silk, College of Textile and Clothing
Engineering, Soochow University, Suzhou 215123, China. E-mail: yklai@suda.edu.cn
b
School of Materials Science and Engineering, Nanyang Technological University, 50
Nanyang Avenue, Singapore 639798, Singapore
c
Research Center of Cooperative Innovation for Functional Organic/Polymer Material
Micro/Nanofabrication, Soochow University, Suzhou 215123, China
Cite this: J. Mater. Chem. A,2017,5,31
Received 14th September 2016
Accepted 26th October 2016
DOI: 10.1039/c6ta07984a
www.rsc.org/MaterialsA
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animals and creatures. Great eorts were devoted to the
understanding of the relationship between the structures and
special wet tability of natural creatures and fabricatin g arti -
cial superhydrophobic surfaces. Such superhydrophobic
characteristics have been widely explored for self-cleaning,
anti-fogging/fro sting, oil/water separation, and anti-bio-
adhesion applications.
Recently, dierent micro/nanoscale binary structured
super hydrophobic surfaces with a high static water contact
angle and low hys teresis have opened up new possibilities of
applications in industrial and biological elds.
510
Textiles, for
example, are intrinsically porous, rough, exibl e and hydro-
phili c. At the as-fabricated state, they absorb both water and
oil.
11,12
For apparent reasons, it is desirable to modify the
hydrophilic textile with low surface energ y materials in orde r to
overcome the intrinsic weakness for a number of appli cations.
It would require unique micro/nanostr uctures inspir ed by
nature to enable special wettability for the textile ind ustry.
Cloths with oilwater separation are valuable to combat the
problems caused by oil spill accidents.
13,14
Moreover, other
novel multifuncti onal applications for superhydrophobic
textiles started to merge, includi ng UV-blocking, photo-
catalytic, ame-retardant, asymmetric superhydrophobic/
super hydrophilic, and stimuli -responsive. These represent
potentially high value-added textiles that can be realise d by
relatively simple chem ical treat ment. However, there are
potential issues for the health and safety of the workers and
consumers during processing and usage. Thus, attention
should be paid to research on envir onmentally friendly prep-
arati on methods, as well as durability and mechanical stability
of the textiles.
Fig. 1 Lotus leaves in nature: self-cleaning behaviour (a) and the
related microstructures as observed by scanning electron microscopy
(b), protrusions (c) and the wax tubules on them (d). (Reprinted from
ref. 4 with permission).
Zhong Chen obtained his Ph.D. in
1997 at the University of
Reading, U.K. Aer completing
the study, he joined the newly
established Institute of Materials
Research and Engineering,
a national research institute
funded by Singapore government.
In March 2000, he moved to
Nanyang Technological Univer-
sity as an Assistant Professor,
and has since been promoted to
Associate Professor and Professor
in the School of Materials Science and Engineering. Prof. Chen's
research interests include Surface Engineering, Thin Films &
Nanostructured Materials, and Mechanical Behaviour of Materials.
He is an author of over 200 SCI journal papers, 5 book chapters and
5 granted patents.
Guoqiang Chen is a professor in
the College of Textile and
Clothing Engineering at Soo-
chow University (China). He
received his Ph.D. degree in
textile chemistry and dyeing &
nishing engineering at Dong-
hua University (China). He
pursues research and develop-
ment of textile chemicals and
functional textiles. He has pub-
lished more than 250 papers. He
serves as Editor-In-Chief of
Modern Silk Science and Technology. He has received several
prizes (State Science and Technology Awards, Mulberry and Flax
Prize of Hong Kong). He is vice president of the China Silk
Association.
Yuekun Lai received his Ph.D.
degree from the Department of
Chemistry, Xiamen University.
During 20092011, he worked
as a research fellow at the
School of Materials Science and
Engineering, Nanyang Techno-
logical University, Singapore.
Aer that, he moved to Muenster
University with Prof. Harald
Fuchs and Prof. Lifeng Chi under
the support of the Humboldt
Foundation Scholarship of Ger-
many. He is currently a professor at National Engineering Labo-
ratory for Modern Silk, and School of Textile and Clothing
Engineering in Soochow University since 2013. His research
interests focus on the bio-inspired intelligent surfaces with special
wettability, and energy & environmental materials.
32 | J. Mater. Chem. A,2017,5,3155
This journal is © The Royal Society of Chemistry 2017
Journal of Materials Chemistry A Review
Open Access Article. Published on 26 October 2016. Downloaded on 8/26/2022 6:17:40 AM.
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2. Characterization of
superhydrophobic surfaces
Generally, the surface with static water angle q
CA
> 150
and
sliding angle q
SA
<10
is dened as superhydrophobic.
However, the denitions of the hydrophobic state are divided
into two camps. One believe that the solid surface with a contact
angle q
CA
>90
was considered as hydrophobic according to
Young' equation. The other view by Volger et al. suggested that
aCAof65
divides solid materials into hydrophobic and
hydrophilic using a surface force apparatus supported by
ancillary techniques.
15
Specically, attractive forces appeared
when two planes exhibited a water CA > 65
. In contrast,
repulsive forces were detected between surfaces with q <65
.
This result clearly demonstrates that the new division of
hydrophilicity and hydrophobicity should be 65
rather than
90
when considering the chemical and structural states of
water droplets. Similar to this research, Jiang et al. found that
an angle of 62.7
could distinguish hydrophilicity and hydro-
phobicity aer investigating the apparent and intrinsic CA of
many polymeric materials.
16
Therefore, the two general routes
to fabricate superhydrophobic surfaces can be summarized as
follows: constructing appropriate roughness on the material
surface or chemically modifying the material surface to be
hydrophobic with a contact angle > 65
.
The simplest method to evaluate a superhydrophobic
surface is by visualization with eye. When a ow of water is
applied on the substrate surface, an intuitional wetting behav-
iour and a self-cleaning phenomenon are observed. However, it
is essential to characterize the superhydrophobic property
quantitatively with precise determination of the static water
contact angle (WCA) and contact angle hysteresis (CAH).
Notably, superhydrophobic surfaces with a similar water
contact angle q
CA
> 150
can exhibit completely dierent contact
angle hysteresis.
17,18
To distinguish among the dierent super-
hydrophobic states, ve typical wetting states have been dened
(Fig. 2ae):
19
totally wetting superhydrophobic surfaces in the
Wenzel state, totally air-supporting superhydrophobic surfaces
in the Cassie state, the metastable state between the Wenzel and
Cassie states (including a petal state), surfaces in the micro/
nanostructured two-tier lotus state, and a partially wetting
gecko state. Nature also provides several examples of aniso-
tropic superwettability. For example, water droplets easily roll
along the direction parallel to the rice leaf edge but not in the
perpendicular direction.
20
Similar to rice leaves, buttery wings
(Fig. 2g) also exhibit anisotropic rolling/pinning super-
hydrophobic states.
21
In addition to these low-adhesion super-
hydrophobic examples, some organisms also provide examples
of high-adhesion superhydrophobic properties, such as gecko
feet (Fig. 2j).
2224
Generally, there are three important wetting theories to
explain the surface wettability: the Young model, Wenzel model
and CassieBaxter model. The Young equation assumes that the
surface is totally smooth and the static contact angle is deter-
mined by the interfacial energies between the solidvapour
phase, solidliquid phase, and liquidvapour phase. However,
most solid surfaces in reality are rough and this has put
a limitation on Young's model in explaining the surface wetta-
bility behaviour. Wenzel revised the Young equation and sug-
gested that the real contact area increases on a roughened
surface. In the Wenzel state, the liquid is considered to be in
complete contact with the rough solid surface so it is dicult
for the water droplet to move and roll o the surface due to the
larger contact area and stronger adhesion. Subsequently, Cassie
and Baxter proposed a heterogeneous contact model where the
liquid is on top of the rough surface with air trapped in
between. Therefore, a water droplet is easy to move and roll o
the surface, which is described as a slippy surface.
25
Theo-
retical analysis has conrmed that the Wenzel state corre-
sponds to a lower energy level.
26,27
The presence of surface
energy between these two states may prevent the spontaneous
transition from the Cassie state to Wenzel state, but it is
conrmed that the two models can transit from one to the other
under specic conditions.
2.1 Static water contact angle
Thomas Young was the rst to consider the contact angle of
a water droplet on a completely smooth substrate in relation to
the interfacial energies acting between solidliquid (g
sl
), solid
vapor (g
sv
) and liquidvapour (g
lv
) interfaces in the well-known
Young's equation:
cos q
ca
¼
g
sl
g
sv
g
lv
(1)
The equation assumed an ideal state that the surfaces are
chemically homogeneous, atomically smooth and the surface
wettability is dependent on the chemical composition at the
interfaces. However, even for the low surface energy material
(e.g., C9 peruorocarbon) modied substrate, the static water
contact angle can only reach 105
118
,
28
which is below the
dened superhydrophobic contact angle of 150
. Therefore, the
surface roughness is very necessary to fabricate super-
hydrophobic surfaces. Two dierent wetting models, including
the Wenzel model and the Cassie model, are developed to
explain the wetting behaviour of the roughness substrate since
the actual surface is not absolutely smooth. In the textile eld,
a commonly employed strategy is to construct nano-micro-
roughness using particles and to modify the surface using
a low surface energy material. Although many literature stud-
ies reported successful attempts for superhydrophobic
anti-wetting textile through a novel one-step deposition of
Fig. 2 Five typical cases for anti-wetting surfaces (a: Wenzel state; b:
Cassie state; c: WenzelCassie state; d: lotus state; e: gecko state)
and several common phenomena for anti-wetting in nature (f: petal; g:
buttery; h: strider; i: lotus leaf; j: gecko).
This journal is © The Royal Society of Chemistry 2017 J. Mater. Chem. A,2017,5,3155 | 33
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a uoroalkylsilane polymer, concerns exist over the stability and
durability, as well as the potential toxicity of uorine-containing
molecules to the environment.
Both the Wenzel model and Cassie model claried the
mechanism of wettability on the roughness surface and
demonstrated that surface roughness and low surface energy
are two equally critical factors for constructing the extreme
wetting surface states. The Wenzel and Cassie model equations
are given in eqn (2) and (3) respectively:
cos q
w
¼ g cos q
e
(2)
cos q
r
¼ f
s
(cos q +1) 1 (3)
In the Wenzel state, a liquid droplet is in complete contact
with the substrate and the static contact angle is proportional to
the contact angle on the at surface and the surface roughness
factor (r) (eqn (2)). The surface roughness factor (r)isdened as
the ratio of the actual contact area and the projected surface
area. In this situation, the surface roughness factor is always
larger than one; thus for a hydrophobic surface, the hydro-
phobic property improves (i.e. the actual contact angle
increases) with increasing surface roughness. Moreover, the
surface roughness is also benecial to improve wetting by
making the contact angle smaller for a hydrophilic state (WCA <
90
). When water is not able to completely wet the rough
substrate surface due to protrusions and recessed areas with
trapped air in between, the Cassie model (eqn (3)) becomes
applicable. The Cassie model is based on water contact with
a composite surface of the solid and air that is trapped into the
microgrooves of the rough surface. In eqn (3), f
s
is the fractional
contact area. Based on this equation, the contact angle
increases with increasing fractional airliquid contact dened
by (1 f
s
). Therefore, to obtain a superhydrophobic surface, it is
very necessary to design fractal dimensions of the rough surface
for enlarging the contact area of liquid and air. So altering the
surface free energy or fabricating the roughness surface struc-
ture or both can achieve a superhydrophobic surface.
2.2 Contact angle hysteresis
As stated earlier, the superhydrophobic surface exhibits various
dynamic characteristics and can be potentially applied for
various applications including self-cleaning, anti-corrosion,
anti-biology adhesion, and snow-pinning prevention. The
criterion to judge a superhydrophobic surface is not only by the
static liquid contact angle, but also the dynamic contact angle.
For a dynamic water droplet, there are two contact angles, the
so-called advancing contact angle (q
Adv
) and the receding
contact angle (q
Rec
). The dierence between them is dened as
contact angle hysteresis (CAH). Generally speaking, a true
superhydrophobic surface means not only a high static contact
angle, but also a low contact angle hysteresis because the low
hysteresis ensures easy rolling o of the water droplets,
favourable for self-cleaning. Therefore, the contact angle
hysteresis is a vital parameter for the characterization of the
super-antiwetting surface. The q
Adv
and q
Rec
are typically
measured using a commercial instrument with a professional
and enhanced video microscope system with digital image
analysis tools.
Two technologies are oen used to measure the contact
angle hysteresis, one is the dosing/decreasing method and the
other is the tilting plate method (Fig. 3a and b). Some signi-
cant dierences in the results have been reported between the
two methods.
2932
For example, the advancing angle and
receding angles were measured in a Kr
¨
uss DSA 100 (Germany)
optical contact angle instrument. A syringe pump is used to
generate a water droplet with controllable amounts. The rate of
water pumping through the needle can also be controlled. Aer
generating a water droplet, the volume of water droplet is
further increased by further pumping water at a very low speed
through the needle. At the beginning, the contact area between
the water droplet and solid substrate does not change but the
contact angle increases with increasing water droplet volume.
When the water volume increases to a critical value, the three
phase (liquid, solid, and air) contact line begins to move
forward. We dene the contact angle before the contact line
change as the advancing angle. Similarly, when sucking the
water back into the needle at a slow rate, the contact angle is
prone to decrease with the decreasing liquid volume. The value
of the receding angle is recorded at the point when the contact
area begins to change. The nal q
Adv
and q
Rec
are recorded
simultaneously by a frame grabber using a charge coupled
camera. Another method is by using a tilting plate, the tilt angle
refers to the critical angle between the substrate and the hori-
zontal surface, above which the droplet starts to move. It should
be pointed out that the tilt angle reects, but is not equal to the
dierence between q
Adv
and q
Rec
.
33
2.3 Sliding angle
The sliding angle is empirical data to characterize a specic
wettability surface. A low sliding angle is crucial to self-cleaning
application. The sliding angle, also known as roll-o angle, is
the one of the inclinations when the water droplet completely
rolls o the surface without an external force. In the experi-
ment, the contact angle measurement instrument is equipped
Fig. 3 Schematic illustrations of the technologies for characteriza-
tion of the contac t angle hyste resis: the ad vancin g angle Q
Adv
and
the recedin g angle Q
Rec
(a and b), sliding angle or rol ling angle Q
SA
(c and d).
34
| J. Mater. Chem. A,2017,5,3155
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Journal of Materials Chemistry A Review
Open Access Article. Published on 26 October 2016. Downloaded on 8/26/2022 6:17:40 AM.
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with a tilting plate with a tunable angle from 0
to 360
. The tilt
angle is increased continuously from 0
to 90
, and the angle is
recorded as q
SA
when the droplet is sliding away or rolling o
the surface.
3436
There are mainly two methods to measure the
sliding or roll-o angle based on the original state of water
droplet contact with the substrate. Typically, a certain volume of
water droplets is placed on a solid surface and the tilting plate
then begins to tilt at a constant speed (Fig. 3c). When the water
droplet slides or rolls o the surface, the tilt angle is regarded as
the sliding angle. In most cases, researchers choose this
method to obtain the sliding angle and it is convenient for
macroscopically at surfaces. For macroscopically rough
surfaces, another technique is adopted, where a water droplet of
dened volume is released onto the substrate with a certain
height. The critical angle of inclination at which the substrate
needs to be tilted until the droplet rolls o the surface is dened
as the sliding angle (Fig. 3d). Several parameters need to be
controlled and recorded in this case: the tilt angle of the
substrate, the distance between the needle and substrate, the
relative distance of the impact point to the lower end of the
substrate, and the liquid volume.
2.4 Adhesive force
Normally, adhesive force is a direct index to evaluate the liquid
solid adhesion. Compared with the common static contact
angle and dynamic sliding angle, there are much less literature
studies reporting the adhesive force on the superhydrophobic
surface. For the self-cleaning surface such as lotus leaves, well
recognized as the Cassie state, water droplets cannot easily rest
stable on the surface, demonstrating an ultralow adhesion force
between the liquid and the substrate. However, an opposite
example is the partially wetted gecko feet, which have
extremely strong adhesive force that allows it to walk up and
down on a vertical wall. Generally, a low adhesion force corre-
sponds to a low sliding angle. The adhesion force of a super-
hydrophobic surface with a high static contact angle and a low
sliding angle should be very small. Reversely, a surface with
a lower adhesive force between the water droplet and substrate
must exhibit excellent superhydrophobicity. The adhesive force
is measured using a high-sensitivity micro-electrochemical
balance system (Dataphysics DCAT11, Germany). A metal ring
containing a certain volume of water droplets is placed above
the sample and the sample table approaches, contacts and
nally leaves the metal ring with a constant speed. The
maximum force value (break peak point) measured during the
sample table leaving process is taken as the value of adhesive
force.
3. Fabrication technologies of
superhydrophobic textiles
As discussed above, there are two signicant factors in fabri-
cating a superhydrophobic surface: the appropriate hierarchical
structure with durable micro/nanoparticles and a low energy
surface. For textiles with a micro-scale bre structure,
a common strategy is to coat nanoscale particles onto the bre
surface to achieve the micro/nanoscale structure and subse-
quently post-uorinate the hierarchical structure for the
low energy. The most common methods for preparing robust
superhydrophobic textile surfaces include physical and
chemical approaches, such as dip-coating,
3745
wet chemical
deposition,
4649
electro-assisted chemical deposition,
5054
spray-
coating,
5557
solgel,
5862
chemical etching,
6366
chemical vapour
deposition,
6770
plasma processing,
7174
and polymer gra-
ing.
7580
These available fabrication technologies will be sepa-
rately discussed in the following categories: (i) pre-roughening
and post-uorinating, and (ii) simultaneous roughening and
uorinating (one-pot method).
3.1 Pre-roughening and post-uorinating
The pre-roughening and post-uorinating technology is the
most common method available to date in preparation of
cellulose-based superhydrophobic textile surfaces. Functional-
ization with nanoparticles or nanolaments or a layer of lm
can usually achieve the required roughness. Nanoparticles such
as SiO
2
, TiO
2
, and ZnO are oen used to decorate textiles'
surfaces to generate a roughness and durable super-
hydrophobic surface. In addition, some inorganic or organic
chemical materials in the form of nanolaments, nanobres
and even lm layers are also reported in the literature to
fabricate superhydrophobic cellulose-based surfaces. In this
section, we will discuss in detail the fabrication technologies
based on the formation type (particles, nanolaments, nano-
bre, and lm) on the textile surfaces.
3.1.1 Dip-coating method. Wang et al.
37
fabricated
a superamphiphobic fabric with a signicant self-healing eect
against both physical and chemical damages via a two-step wet
chemical route. As shown in Fig. 4, the cleaned fabric is
immersed in a uoroalkyl surface-modied silica nanoparticle
solution for 5 minutes and then coated in uorinated decyl
polyhedral oligomeric silsesquioxane (FD-POSS) and uo-
roalkylsilane (FAS) solution. The surface of polyester fabric
exhibits a distinct protrusion structure aer coating while the
Fig. 4 (a) Chemical structures of coating materials and procedure for
coating treatment. SEM images of (b) uncoated and (c) coated poly-
ester bres. The relationship of the CA (d) and SA (e) with surface
tension and the CA changes of water, hexadecane and ethanol with
time (f). (Reprinted from ref. 37 with permission).
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Citations
More filters
Journal ArticleDOI
TL;DR: A review of the recent progress of oil/water separation technologies based on filtration and absorption methods using various materials that possess surface superwetting properties is presented in this article.
Abstract: Oil/water separation is a field of high significance as it has direct practical implications for resolving the problem of industrial oily wastewater and other oil/water pollution. Therefore, the development of functional materials for efficient treatment of oil-polluted water is imperative. In this feature article, we have reviewed the recent progress of oil/water separation technologies based on filtration and absorption methods using various materials that possess surface superwetting properties. In each section, we present in detail representative work and describe the concepts, employed materials, fabrication methods, and the effects of their wetting/dewetting behaviors on oil/water separation. Finally, the challenges and future research directions of this promising research field are briefly discussed.

762 citations

Journal ArticleDOI
TL;DR: Superhydrophobicity is the tendency of a surface to repel water drops as discussed by the authors, and it is defined as the ability of the surface to resist water drops in nature.
Abstract: Superhydrophobicity is the tendency of a surface to repel water drops. A surface is qualified as a superhydrophobic surface only if the surface possesses a high apparent contact angle (>150°), low contact angle hysteresis (<10°), low sliding angle (<5°) and high stability of Cassie model state. Efforts have been made to mimic the superhydrophobicity found in nature (for example, lotus leaf), so that artificial superhydrophobic surfaces could be prepared for a variety of applications. Due to their versatile use in many applications, such as water-resistant surfaces, antifogging surfaces, anti-icing surfaces, anticorrosion surfaces etc., many methods have been developed to fabricate them. In this article, the fundamental principles of superhydrophobicity, some of the recent works in the preparation of superhydrophobic surfaces, their potential applications, and the challenges confronted in their new applications are reviewed and discussed.

350 citations


Cites background from "A review on special wettability tex..."

  • ...This results in a slippery contact surface that increases the mobility of liquid drops favoring the easy sliding action of liquid drops.(35,36) If the Cassie–Baxter state is maintained, the drop of liquid can easily move/roll across the solid surface....

    [...]

Journal ArticleDOI
01 Jan 2020
TL;DR: In this article, a comprehensive survey of the progress achieved so far in the production of super-hydrophobic materials based on cellulose and fiber networks is presented, focusing on summarizing some of the aspects that are critical to advance this evolving field of science which may provide new ideas for the developing and exploring of super hydrophobic and green-based materials.
Abstract: Superhydrophobic cellulose-based products have immense potential in many industries where plastics and other polymers with hydrophobic properties are used. Superhydrophobic cellulose-based plastic is inherently biodegradable, renewable and non-toxic. Finding a suitable replacement of plastics is highly desired since plastics has become an environmental concern. Despite its inherent hydrophilicity, cellulose has unparalleled advantages as a substrate for the production of superhydrophobic materials which has been widely used in self-cleaning, self-healing, oil and water separation, electromagnetic interference shielding, etc. This review includes a comprehensive survey of the progress achieved so far in the production of super-hydrophobic materials based on cellulose and fiber networks. The method-ologies and applications of superhydrophobic-modified cellulose and fiber networks are emphasized. Overall, presented herein is targeting on summarizing some of the aspects that are critical to advance this evolving field of science which may provide new ideas for the developing and exploring of superhydrophobic and green-based materials.

283 citations


Cites background or methods from "A review on special wettability tex..."

  • ...Since then, research interests on super-hydrophobicity have grown tremendously, with numerous studies devoted to mimicking natural plants, animals and creatures (Li et al., 2017)....

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  • ...Moreover, the as-prepared fabric and sponge via the in-situ growth method followed by thiol modification possess anti-wettability towards water and can selectively absorb and filtrate oils from water with high efficiency (Li et al., 2017)....

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  • ...From this perspective, it is essential to create liquid repellent coating with long-term durability, self-healing and non-toxicity, which is believed to be an efficient way to overcome the poor durability caused by physical and chemical damages (Li et al., 2017)....

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  • ...of superhydrophobic surfaces have great potential applications in aircrafts, optical lenses, energy transmission system, power lines, wind turbines, and highways as well as building constructions (Li et al., 2017)....

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Journal ArticleDOI
Xuejie Yue1, Zhangdi Li1, Tao Zhang1, Dongya Yang1, Fengxian Qiu1 
TL;DR: In this paper, the theory and design of various superwetting states for selective oil/water separation including superhydrophobicity/superoleophilicity, super-hydrophilicity/underwater superoleophobicity, Janus wettability, and smart Wettability are discussed.

249 citations

Journal ArticleDOI
03 May 2018
TL;DR: It is expected that the biomimetic porous materials with nanoscale interface engineering will overcome the current challenges of oil-water emulsion separation, realizing their practical applications in the near future with continuous efforts in this field.
Abstract: Oil–water separation is critical for the water treatment of oily wastewater or oil-spill accidents. The oil contamination in water not only induces severe water pollution but also threatens human beings’ health and all living species in the ecological system. To address this challenge, different nanoscale fabrication methods have been applied for endowing biomimetic porous materials, which provide a promising solution for oily-water remediation. In this review, we present the state-of-the-art developments in the rational design of materials interface with special wettability for the intelligent separation of immiscible/emulsified oil–water mixtures. A mechanistic understanding of oil–water separation is firstly described, followed by a summary of separation solutions for traditional oil–water mixtures and special oil–water emulsions enabled by self-amplified wettability due to nanostructures. Guided by the basic theory, the rational design of interfaces of various porous materials at nanoscale with special wettability towards superhydrophobicity–superoleophilicity, superhydrophilicity–superoleophobicity, and superhydrophilicity–underwater superoleophobicity is discussed in detail. Although the above nanoscale fabrication strategies are able to address most of the current challenges, intelligent superwetting materials developed to meet special oil–water separation demands and to further promote the separation efficiency are also reviewed for various special application demands. Finally, challenges and future perspectives in the development of more efficient oil–water separation materials and devices by nanoscale control are provided. It is expected that the biomimetic porous materials with nanoscale interface engineering will overcome the current challenges of oil–water emulsion separation, realizing their practical applications in the near future with continuous efforts in this field.

240 citations

References
More filters
Journal ArticleDOI
30 Apr 1997-Planta
TL;DR: It is shown here for the first time that the interdependence between surface roughness, reduced particle adhesion and water repellency is the keystone in the self-cleaning mechanism of many biological surfaces.
Abstract: The microrelief of plant surfaces, mainly caused by epicuticular wax crystalloids, serves different purposes and often causes effective water repellency. Furthermore, the adhesion of contaminating particles is reduced. Based on experimental data carried out on microscopically smooth (Fagus sylvatica L., Gnetum gnemon L., Heliconia densiflora Verlot, Magnolia grandiflora L.) and rough water-repellent plants (Brassica oleracea L., Colocasia esculenta (L.) Schott., Mutisia decurrens Cav., Nelumbo nucifera Gaertn.), it is shown here for the first time that the interdependence between surface roughness, reduced particle adhesion and water repellency is the keystone in the self-cleaning mechanism of many biological surfaces. The plants were artificially contaminated with various particles and subsequently subjected to artificial rinsing by sprinkler or fog generator. In the case of water-repellent leaves, the particles were removed completely by water droplets that rolled off the surfaces independent of their chemical nature or size. The leaves of N. nucifera afford an impressive demonstration of this effect, which is, therefore, called the “Lotus-Effect” and which may be of great biological and technological importance.

5,822 citations

Journal ArticleDOI
TL;DR: In this article, a super-hydrophobic surface with both a large contact angle (CA) and a small sliding angle (α) has been constructed from carbon nanotubes.
Abstract: Super-hydrophobic surfaces, with a water contact angle (CA) greater than 150degreesC, have attracted much interest for both fundamental research and practical applications. Recent studies on lotus and rice leaves reveal that a super-hydrophobic surface with both a large CA and small sliding angle (alpha) needs the cooperation of micro- and nanostructure, and the arrangement of the microstructures on this surface can influence the way a water droplet tends to move. These results form the natural world provide a guide for constructing artificial super-hydrophobic surfaces and designing surfaces with controllable wettability. Accordingly, super-hydrophobic surfaces of polymer nanofibers and differently patterned aligned carbon nanotube (ACNT) films have been fabricated.

3,781 citations