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1
Nanostructuring surfaces to control wetting
Frontiers in Physical Sciences, Buenos Aires Nov. 14th - 18th , 2016
Hans-Jürgen Butt
Max Planck Institute for Polymer Research Mainz
2
Wetting
Gas Pure liquid Ideal solid
or Real liquid Real solid
?
Mixtures Solutions Surfactants Melts, …
Soft Structured
Heterogeneous Reactive
…
3
Nanostructuring surfaces
to control wetting
Dynamic Hydrophilic Hydrophobic
Water
Solid > 90°
Smooth, planar surface: 120°
Receding Advancing
www.taz.de/uploads/images/684x342/9559867.jpg
4
Nanostructuring surfaces
to control wetting
Oil
Solid
Smooth, planar surface: < 90°
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How to make super liquid-repellent surfaces?
Water
> 150°
Oil
superhydrophobic superoleophobic
superamphiphobic
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Superhydrophobic surfaces
Fogg, Nature 1944, 154, 515 Contact angle on wheat leaves: 152°
www. birkenhof-tuningen.de
Cassie & Baxter, Nature 1945, 155, 21
Entrapped air High apparent contact angle Water
Solid
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Superhydrophobic surfaces
Dettre & Johnson, SCI Monograph 1967, 25, 144
Aritificial structures with app > 150° and < 10°
Neinhuis & Barthlott, Ann. Botany 1997, 79, 667; Planta 1997, 202, 1
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Castor oil <90°
Water 120°
Tsujii et al., Angew. Chem. 1997, 36, 1011; Tuteja, McKinley & Cohen, Science 2007, 318, 1618; Herminghaus, EPL 2000, 52, 165; Bernardino, Blickle & Dietrich, Langmuir 2010, 26, 7233; Blow & Yeomans, Langmuir 2010, 26, 16071
Superhydrophobic
Water
Roughness
Superamphiphobic
Oil
Overhangs
Superoleophobic surfaces
Low energy surface
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Superoleophobic surfaces
Science 2012, 335, 66
Soot-templated
200 nm
Tuteja et al., PNAS 2008, 105, 18200
Lithography
Electrospun fibres
Liu & Kim, Science 2014, 346, 1096
Tables with overhanging rim
Veinot et al., Langmuir 2007, 23, 5275 Zhang & Seeger, Angew. Chem. 2011, 50, 6652
Nanofilaments
10
400 nm
100 nm 100 nm
200 nm
100 nm
Tetraethoxysilane +
600°C, 2 h +
Fluorosilane
Superamphiphobic surfaces
Xu Deng
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Superamphiphobic surfaces
Soot
Highly porous soot
aggregates
SiO2 coating
Tetraethoxy-silane
+ Fluorosilane
600°C
Science 2012, 335, 67
12
Superamphiphobic surfaces
Soot
Highly porous soot
aggregates
SiO2 coating + Fluorosilane
600°C
Liquid
SiO2
50-100 nm
Science 2012, 335, 67
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water droplet (6 µL)
water
Potential applications
Anti fogging
Anti icing
Anti biofouling
Drag reduction
Gas exchange
Microsphere
…
Self-cleaning
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Superamphiphobic membranes for blood oxygenation
Nature Commun. 2013, 4, 2512
Human blood stabilized by heparin as anticoagulant after 24 h incubation at 37°C
Mailänder
Schöttler
Landfester
XPS
Weidner
Bonn
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Understanding
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Microscopic structure contact angle
Bico, Marzolin & Quéré, EPL 1999, 47, 220; Öner & McCarthy, Langmuir 2000, 16, 7777
cosapp = f(cos +1)-1
Cassie & Baxter, Trans. Faraday Soc. 1944, 40, 546
app
17
Bico, Marzolin & Quéré, EPL 1999, 47, 220; Öner & McCarthy, Langmuir 2000, 16, 7777
cosapp = f(cos +1)-1
Cassie & Baxter, Trans. Faraday Soc. 1944, 40, 546
app
Global thermodynamic equilibrium
Hypothesis
Advancing and receding are fundamentally different
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How does a drop advance and recede on a superhydrophobic surface?
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Superhydrophobic micropillar surface
a = 5 µm, b = 15 µm 10 30 25 75
SU8 + 70 nm SiO2 + perfluorooctyltrichlorosilane
Water
Solid
Advancing aapp = 1653°
Receding rapp = 1425°
Substrate
Air
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Superhydrophobic micropillar surface
Laser scanning confocal microscope
21 21
Advancing water front
8°
Substrate
Water Air
22
Advancing water front
a = 5 µm, b = 15 µm
Phys. Rev. Lett. 2016, 116, 096101
Advancement is touch down a
app = 180°
23 23
Receding water front
8°
Substrate
Water
Air
24
Receding water front
a = 5 µm, b = 15 µm
Phys. Rev. Lett. 2016, 116, 096101
The apparent receding contact angle is defined and characteristic
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Advancing and receding are fundamentally different processes
Use apparent receding contact angle to characterize superliquid repellent surfaces
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Design of superamphiphobic surfaces
A0
2R
Ciro Semprebon MPI Martin Brinkmann Stephan Herminghaus Matteo Ciccotti ESPCI
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Design of superamphiphobic surfaces
A0
2R
Impalement
• High R/A0 ratio
Soft Matter 2013, 9, 418
28
Design of superamphiphobic surfaces
a
2R
app
• Low R/a ratio
High app
• High R2/a2 ratio
High shear strength
Soft Matter 2013, 9, 418
29
Design of superamphiphobic surfaces
• Low R/A0 ratio
Drag reduction Large slip length b
b
vs
rc
Soft Matter 2013, 9, 418
30
Design of superamphiphobic surfaces
2R
a
Impalement pressure high R/a2
App. contact angle low R/a
Slip length low R/a2
Shear strength high R2/a2
Soft Matter 2013, 9, 418
31
Conclusions
High apparent receding
contact angle
High impalement pressure
Mechanically robust
Challenge:
Advancing and receding are fundamentally different processes
Use apparent receding contact angle to characterize superliquid repellent surfaces
32
Thanks!
Collaborations:
Kremer, Bonn
ESPCI Paris
MPI Göttingen
TU Darmstadt
Uni. Twente
…
Thanks for your attention!