nanostructuring surfaces to control wetting · cos app = f(cos +1)-1 cassie & baxter, trans....

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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

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Wetting

Gas Pure liquid Ideal solid

or Real liquid Real solid

?

Mixtures Solutions Surfactants Melts, …

Soft Structured

Heterogeneous Reactive

…

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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

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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

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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

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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

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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

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Advancing water front

8°

Substrate

Water Air

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Advancing water front

a = 5 µm, b = 15 µm

Phys. Rev. Lett. 2016, 116, 096101

Advancement is touch down a

app = 180°

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Receding water front

8°

Substrate

Water

Air

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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

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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

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Design of superamphiphobic surfaces

• Low R/A0 ratio

Drag reduction Large slip length b

b

vs

rc

Soft Matter 2013, 9, 418

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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

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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

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Thanks!

Collaborations:

Kremer, Bonn

ESPCI Paris

MPI Göttingen

TU Darmstadt

Uni. Twente

…

Thanks for your attention!