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°

5

How to make super liquid-repellent surfaces?

Water

> 150°

Oil

superhydrophobic superoleophobic

superamphiphobic

6

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

7

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

8

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

9

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

11

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

13

water droplet (6 µL)

water

Potential applications

Anti fogging

Anti icing

Anti biofouling

Drag reduction

Gas exchange

Microsphere

…

Self-cleaning

14

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

15

Understanding

16

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

18

How does a drop advance and recede on a superhydrophobic surface?

19

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

20

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

25

Advancing and receding are fundamentally different processes

Use apparent receding contact angle to characterize superliquid repellent surfaces

26

Design of superamphiphobic surfaces

A0

2R

Ciro Semprebon MPI Martin Brinkmann Stephan Herminghaus Matteo Ciccotti ESPCI

27

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!