Master Class

1
30 November 2006
Master Class
Erika Eiser René Williams, Jeroen Goedkoop
2
Nano-technologies inspired by Nature
3
(No Transcript)
4
The Lotus effect
Nelumbo nucifera, the sacred lotus flower.
5
Many plants show the phenomena that water
droplets do not wet their leaves.
6
Surface tensions
vapor
?lv liquid/vapor
liquid
?ls liquid/solid
?sv solid/vapor
solid
Youngs equation
7
poor wetting
good wetting
complete wetting
? gt 90C
90 gt ? gt 0
? ? 0
?lv
?lv
?lv
?ls
?
?sv
?
?
cos? lt 0
cos? 0
cos? gt 0
8
Wetting is a physical property, purely driven by
surface energies!!
9
There are 2 factors that render surfaces even
more hydrophobic.
http//www.botanik.uni-bonn.de/system/lotus/en/pri
nzip_html.htmldas
10
Surface roughness
Only ? ?180 can be reached!

• amplifies wetting on hydrophilic surfaces
• reduces wetting on hydrophobic surfaces

11
The energy cost to wet a hydrophobic surface with
water is larger than to wet the solid surface
with air (?sv lt ?sl) The liquid drop will try to
minimize its contact area with the solid,
leaving air pockets underneath!
J. Bico et al., Europhys. Lett., 47 (2), pp.
220-226 (1999) J. Bico et al. / Colloids and
Surfaces A Physicochem. Eng. Aspects 206 (2002)
42 4146
12

• Micro- or nanopatterning an already hydrophobic
  surface will make that surface even more
  hydrophobic (? gt 150).
• Some call such super-hydrophobic surfaces also
  fakir surface

David Quéré, nature materials, vol. 1, Sept. 2002
13
Where is the connection to Nature?
14
Lotus leaves are known to be extremely
hydrophobic and self-cleaning surfaces.
http//www.botanik.uni-bonn.de/system/lotus/en/lot
us_effect_multimedia.html
15
(No Transcript)
16
? gt 150
http//www.botanik.uni-bonn.de/system/lotus/en/lot
us_effect_multimedia.html
17
We may create new self-cleaning paints or
wallpaper.
Facade paint, self-cleaning with rainfall thanks
to the Lotus-effect
http//www.botanik.uni-bonn.de/system/lotus/en/lot
us_effect_multimedia.html
18
Creating self-cleaning glass coatings.
http//www.nano-products.info/nanotechnologie-auto
scheiben-versiegelung.php
19
poly(tetrafluoroethylene) (PTFE) non-wetting
coating.
Kenneth K. S. Lau et al. Nano Letters 2004
20
http//solutions.3m.com/wps/portal/3M/en_US/VHB/Ta
pes/Product-Information/How-to-use/Design-Tape-Sel
ection/
21
Self-Assembly
22
The magic words that make the handling of
nano-technology feasible are
bottom-up approach self-assembly
23
Biological examples
24
Can we use self-assembly to make our own smart
drugs?
25
Surfactants Surface Active Molecules
Amphiphiles

• Surfactants are molecules with amphiphilic
  character.
• This means the molecules consist of a hydrophobic
  (tail) and hydrophilic (head group) part.

tail
head group
26
Self-assembling soap molecules
http//www.nonequilibrium.com/complexfluids.htm
27
Our Research and what we are going to do today
Sodium dodecyl sulfate (SDS)
Spontaneous self-assembly into wormlike micelles

Pentanol

Water
http//www-its.chem.uva.nl/research/complex_fluids
/
28
Our Research and what we are going to do today
UvA (E.Eiser, A. Gaikward, P.Verschuren)

• Physical questions How do the clusters align?
  How do they influence the crystal growth?...
• Chemistry/Nanotechnology

http//www-its.chem.uva.nl/research/complex_fluids
/
29
Self-Assembly of colloids
30
Natural Colloidal Crystal
31
Bio-mineralization
Butterflies Photonic Crystals
32
Bio-mineralization
Morpho
33
Photonic Band Gap
Photonic crystals

• Allow only a narrow band of visible light pass
• All other wavelength will be blocked
• Just like electrons in a semi-conductor.

34
Photonic Band Gap
Application
New, powerful lasers and optical fibers.
http//policy.iop.org/v_production/v12.html
35
The difficulty
Making photonic crystals with complex structures,
e.g. the diamond structure.
And many more problems will await you.
36
Self-Assembly For biomedical applications
37
T. A. Taton, C. A. Mirkin, and R. L. Letsinger,
Science 289, 1757 (2000).
38
Importance for DNA arrays
Using ssDNA fragments attached to Au-colloids
give a much sharper melting or hybridization
curve. Any mismatch in the ssDNA to be tested
will lead to a shift in the melting
line Therefore test on base-pair mismatches, e.g.
cancer patients can be developed with a much
higher sensitivity.
39
Our Research and what we are going to do today
UvA/Amolf/Edinburgh (E.Eiser, T. Schmatko, W.C.K.
Poon D. Frenkel)
We try to link micron sized colloids
(fluorecently labed) using long DNA strands. Our
aim is to explore new colloidal architectures
that may be interesting for the application of
photonic band-gap materials.
http//www-its.chem.uva.nl/research/complex_fluids
/
40
Quantum dots
Nanometer sized semiconductors (CdSe)
Dr. D. Talapin, University of Hamburg,
http//www.chemie.uni-hamburg.de/pc/Weller/
41
Quantum dots (QDs) nano-sized semiconductor
crystals that, when stimulated by laser light,
can fluoresce in a rainbow of colors for weeks at
a time Nie and colleagues have succeeded in
attaching quantum dots to peptides or antibodies
that recognize specific cancer cells, and then
using the dots to isolate individual cancerous
areas (as in this mouse).
X. Gao and S. Nie, Emory University School of
Medicine
42
Nature has taught us

• Self-assembly is possible by
• Using amphiphilic molecules like
• Soaps,
• Proteins with hydrophobic and hydrophilic patches

43
Thank you for coming listening.