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Thunder Lecture III
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Fudan University 04.04.2006
Nano-Bionik
Micro- and Nanotechnology in Nature
Ingo Rechenberg
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Bionics Biomimicry Biomimetics
What is Bionik ?
The study of the results of biological evolution
from the engineering point of view
from the engineering point of view
Learning from natures way of engineering
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Nano-Bionik
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The topics
The Lotus-Flower-Effect Self-cleaning property
through hydrophobic micro-dots. The
Moth-Eye-Effect The art to be invisible through
optical nano-burls. The Gecko-Foot-Effect
Sticking on the wall through elastic nano-hairs.
The Sand-Skink-Effect Reduction of friction
and wear through nano-thresholds. The
Darkling-Beetle-Effect Collecting dew through
hydrophilic/hydrophobic micro-spots. The
Shark-Scale-Effect Turbulence reduction through
longitudinal micro-grooves. The Water
Strider-Effect To keep dry through micro-hairs
with nano-ridges.
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Nano-patterns in nature
?
?
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The sacred Lotus flower is a symbol of purity in
Asian religions.
The Lotus-Flower-Effect
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The Lotus-Effect
Water droplets roll down the leaf of the Lotus
flower
Glue rolls down the leaf of the Lotus flower
A droplet takes up the dirt while rolling down
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30 µm
Microrelief of the leave
The development of the Lotus-Effect paint
Bionik-product
Self cleaning
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Lotusan facade paint
Standard facade paint
Test areas at the wall of my house after 4 years
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Adhesion gt Cohesion
Adhesion lt Cohesion
Surface tension and wetting angle
Adhesion ltlt Cohesion
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The particles adhere tightly to the surface
Smooth neutral surface The dirt particles are
predominantly overflowed by the water-droplet.
Mirco-burled hydrophobic surface The down
rolling droplet washes the dirt particles away.
Mechanism of the Lotus-Effect
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smooth surface
Lotus-Effect surface
The Lotus-Effect in action
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Lotus-Effect roof tile
Lotus-Effect tie
Prof. Wilhelm Barthlott
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Secondary structure
Lotus leaf
The Lotus-Effect extended
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Water droplet
Water droplet
The Lotus-Effect extended
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The Moth-Eye-Effect
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Micro-optics of the moth eye
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Air
Optical transparent layer
Reflection of the light is avoided by a
continuously increasing refractive index of the
optical medium
Glass
Deception of the light
The little burls on the surface of the optical
medium work as a gentle increase of the
refractive index
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All the light is captured by th eye
Moonlight is not mirrored (predatory!)
Night-flying insect
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Invisible Jelly Fish
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Technological imitation of the nanostructure of a
moth eye. Periodicity of the burls 300 nm.
Glass pane with Moth-Eye-Effect
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The Moth-Eye-Effect
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The wonder of the Gecko toes
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500 000 000 nanohairs
2 kg (theoretically)
Photo M. Moffet
Geckos get a grip using Van-der-Waals-forces
Gecko sticking at the wall
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The seta has 1 000 nanohairs
The Gecko toe has 500 000 microhairs (setae)
Nanostructure of the Gecko toe
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The Gecko effect
Adhesion effect through Van-der-Waals-forces
Technical surface 1
Contact area
Technical surface
Technical surface 2
Nanohairs !
Large contact area large
adhesion force
Small contact area small
adhesion force
Microhair
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Synthetic Gecko hairs necessary for spider man
(New Scientist 15. 05. 2003)
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Gecko-Tape
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?
The Sandfish lives in the Sahara desert
The Sandfish-Effect
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Sandfish ?
Fishing rod
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0 s
The Sandfish
¼ s
½ s
dives down
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Characteristics of the sandfish scales
M. Zwanzig, IZM
Friction
Abrasion
sand flow
Electron emission
8µm
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My Sahara Lab
Field work in the Sahara
GPS
N 31 - 15 02 W 03 - 59 13
Erg Chebbi
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Simple apparatus to measure the dynamic friction
coefficient of flowing sand
Sand tubule
Angular scale
Object platform
Hand lever
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Measurement of the dynamic friction coefficient
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Sand flow is moving
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Sand flow stops
Sandskink Measurement of the angle of sliding
friction
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0
40
0
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0
30
sliding angle
0
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Sahara-Measurement 2002
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5
0
0
Sliding friction Sandfish versus engineering
materials
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Friction measurements with a sand-filled cylinder
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Sand-cylinder measurements 2003
Steel 19
Sliding angle
Sandskink 12 Caudal
Sandskink 18 Cranial
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Sandfish scale under the electron mikroscop (REM)
scale
Sand sflow
8µm
at the back
at th belly
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Sand flow
6 µm
Oblique view of the nano-thresholds
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Sliding direction
Size comparison
Grain of sand upon the thresholds
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Abrasion of the sandfish scales
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The sandskink always looks shiny
while
Man-made things soon get blunt in the desert wind
!
The resistance to abrasion
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Simple apparatus for the abrasion tests
Sandfunnel
Sandblast
Objectplatform
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Impact point of the sandblast
Impact time 10 hours !
Steel
Abrasive spot
Glass
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Glass Magnification 200
Sand abrasion under the microscope
2 hours impact time 20 cm blast height
Scotch tape protected
Sand blast
Sandfish Magnification 1000
Sandfish Magnification 1000
Afterward
Before
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Kenyan Sandboa
Sandskink
Parallel Evolution
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Sandskink
Kenyan Sandboa
Sandskink
Parallel Evolution
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Aporosaura anchita
Sand-diving lizard in the Namib desert
Namib
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Ghobi
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Electrical charging in a sand storm
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Night photo Exposure time 20 s
Discharge spark on the back of the sandskink
after a sand storm
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Triboelectric charging of a glass rod
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Triboelectric charging of a plastic rod
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Electron donator
Electron acceptor
Sandskink scale
Tail
Head
Directed tribo-electricity on the sandskink scales
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Observed by Erno Németh
https//fridolin.tu-freiberg.de/archiv/pdf/Verfahr
enstechnikNXmethErnX748129.pdf
Neutrally charged grain of plastic with
oppositely charged spots
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Observed in Sahara
Sticking chain of sandgrains
Neutrally charged grain of sand can have
oppositely charged spots
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Hypothesis
The directed triboelectric experiment indicates
the ease of an electron exchange from and to the
Sandfish skin
Electric levitation hypothesis
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The effect may work for some seconds, time enough
for the sandfish to escape. After that the
neutralised charge has to be refilled.
Sandfish
Electric levitation hypothesis
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Modern Sand Boarding
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The Darkling-Beetle-Effect
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Fog catching in the Namib desert
made by nature
and
made by humans
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Darkling beetle of the Namib desert
(Stenocara sp.)
Hydrophilic peaks
Hydrophobic burled lowland
similar to the Lotus-Effect
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Hydrophobic burls
Fog droplets
Hydrophilic hills
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Hydrophobic burls
Fog droplets
Hydrophilic hills
Condensation
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Hydrophobic burls
Fog droplets
Hydrophilic hills
To the mouth of the beetle
Collected dew
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Waxen surface
Spray
Air flow
Glass spheres
Fan
Experiment of Parker and Lawrence
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Shark scale
The Shark-Scale-Effect
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0,5 mm
The groove structure of the shark scales
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D
W
Sawtooth-Grooves
W
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Sawtooth-Grooves

Trapezoidal-grooves
Rectangular- grooves
Trapezoidal-grooves
s
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Rectangular- grooves


s
BECHERTs experiments in the Berlin oil-channel
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Advertisement of a new swim suit
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Mounting a riblet foil on the wing of an airbus
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The Water-Strider-Effect
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Water strider skating on water
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Nano-grooves
Water strider
Xuefeng Gao Lei Jiang, Beijing
20 µm
200 nm
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Robostrider
Development of an artificial water strider
B. Chan, D. Hu
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The water spider never gets wet
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10 mm
The hair of the water spider, a model for a new
waterproof suit
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Thank for your attention
www.bionik.tu-berlin.de