Thunder Lecture III

Nano-Bionik

Micro- and Nanotechnology in Nature

Ingo Rechenberg

Shanghai Institute for Advanced Studies

Fudan University 04.04.2006

from the engineering point of view

What is Bionik ?

The study of the results of biological evolution

Learning from nature‘s way of engineering

from the engineering point of view

Bionics Biomimicry

Biomimetics

Nano-Bionik

Bacteria flagellum

Biological receptors

Biological self assembly

Muscle filaments

Protein machines

Micro & nano-structured biological surfaces

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.

The topics

Nano-patterns in nature

Nano-humps

Nano-grooves

Nano-bumpsNano-burls

Nano-spikes

Nano-ladders Nano-knobsNano-ribs

Nano-thresholds

? ?

The Lotus-Flower-Effect

The sacred Lotus flower is a symbol of purity in Asian religions.

The Lotus-Effect®

A droplet takes up the dirt while rolling down

Water droplets roll down the leaf of the Lotus flower

Glue rolls down the leaf of the Lotus flower

Honey rolls down from a “Lotus-Effect-spoon”

Self cleaning

30 μm

Bionik-product

The development of the Lotus-Effect

® paint

Microrelief of the leave

Lotusan facade paintStandard facade paint

Test areas at the wall of my house after 4 years

Surface tension and wetting angle

Adhesion > Cohesion

Adhesion < Cohesion

Adhesion << Cohesion

The Lotus-Effect in action

smooth surface

Lotus-Effect® surface

Prof. Wilhelm Barthlott

Lotus-Effect

® roof tile

Lotus-Effect

® tie

The Lotus-Effect extended

Lotus leaf

1 × 1 cm

engineering imitation

Secondary structure

The Lotus-Effect extended

Water droplet

Water droplet

The Moth-Eye-Effect

Micro-optics of the moth eye

130 x

Micro-burls100 nm Ø

420 x

1050 x

4120 x

light

The little burls on the surface of the optical medium work as a gentle increase of the refractive index

Reflection of the light is avoided by a continuously increasing refractive index of the optical medium

Deception of the light

Air

Glass

Optical transparent layer

Night-flying insect

All the light is captured by th eye

Moonlight is not mirrored (predatory!)

Invisible Jelly Fish

Glass pane withMoth-Eye-Effect

Technological imitation of the nanostructure of a moth eye. Periodicity of the burls: 300 nm.

The Moth-Eye-Effect

400 500 600 700 800Wavelength

nm

Re

flect

ivity

1

2

3

4

5

6

0

%

Without burl pattern

With burl pattern

The wonder of the Gecko toes

Gecko sticking at the wall

500 000 000 nanohairs2 kg (theoretically)

Ph

oto

: M

. Mo

ffetGeckos get a grip using Van-der-Waals-forces

The Gecko toe has 500 000 microhairs (setae)

The seta has 1 000 nanohairs

Nanostructure of the Gecko toe

Technical surface 1

Technical surface 2

Microhair

Nanohairs !

Technical surface

The Gecko effectAdhesion effect through

Van-der-Waals-forces

Small contact area

small adhesion force

Large contact area

large adhesion force

Contact area

Synthetic Gecko hairsnecessary for spider man

(New Scientist 15. 05. 2003)

Gecko-Tape

The Sandfish-Effect

?The Sandfish lives in the Sahara desert

Fishing rod

Sandfish ?

The Sandfish

dives down

0 s

¼ s

½ s

Friction

Abrasion

Electron emission

Characteristics of the sandfish scales

M. Zwanzig, IZM

8µm

sand flow

Fieldworkin theSahara

Erg Chebbi

My Sahara Lab

GPS:

N 31° - 15‘ – 02“

W 03° - 59‘ – 13“

Hand lever

Object platformAngular scale

Sand tubule

Simple apparatus to measure the dynamic friction coefficient of

flowing sand

Measurement of the dynamic friction coefficient

Sand flow is moving

Sand flow stops

20°

18°

Sandskink

Measurement of the angle of sliding friction

Sliding friction: Sandfish versus engineering materials

Sahara-Measurement 2002

0

50

100

150

200

Ski

n k

Sa

nd s

lidin

g a

ng

le

25 0

300

35 0

400

0

Ste

el

Gla

ss Teflo

n

Nyl

on

Friction measurements with a sand-filled cylinder

Skink

Steel

151618202021212121242425252626273030th August

25

20

15

10

5

0

0

0

0

0

0

0

ERG CHEBBI 4. - 31. 8. 2003An

gle

of s

lidin

g fri

ctio

n

Sliding angle:

Steel = 19°

Sandskink = 12° Caudal

Sandskink = 18° Cranial

Sand-cylinder measurements

2003

58 %

Sandfish scale under the electron mikroscop (REM)

8µm

Sand sflow

at the back at th belly

50 nm Ø

scale

Oblique view of the nano-thresholds

6 µm

Sand flow

Size comparison

Grain of sand upon the thresholds

Sli

din

g d

irec

tio

n

Abrasion of the sandfish scales

Man-made things soon get blunt in the desert wind !

The sandskink always looks shiny

while

The resistance to abrasion

Simple apparatus for the abrasion tests

30 cm

Sandfunnel

Sandblast

Objectplatform

Impact point of the sandblast

Impact time: 10 hours !

Abrasive spot:Steel

Glass

Sand abrasion under the microscope

Before Afterward

2 hours impact time

20 cm blast height

Glass Magnification ≈ 200

Sandfish Magnification ≈ 1000 Sandfish Magnification ≈ 1000

Scotch tape protected Sand blast

Sandskink

Parallel Evolution

Kenyan Sandboa

Sandskink

Parallel Evolution

Sandskink Kenyan Sandboa

Sand-diving lizard in the Namib desert

Namib

Aporosaura anchita

Allghoi khorkhoi

The Mongolian Death Worm

lives in the Ghobi dersert

?

Ghobi

Electrical charging in a sand storm

Discharge spark on the back of the sandskink after a sand storm

Night photoExposure time 20 s

Triboelectric charging of a glass rod

Triboelectric charging of a plastic rod

Directed tribo-electricity on the sandskink scales

Electron donatorElectron acceptor

Sandskink scale

Head Tail

Neutrally charged grain of plastic with oppositely charged spots

Observed by Ernő Németh

https://fridolin.tu-freiberg.de/archiv/pdf/VerfahrenstechnikNXmethErnX748129.pdf

Neutrally charged grain of sand can have oppositely charged spots

Observed in Sahara

Stic

king

cha

in o

f sa

ndgr

ains

Hypothesis:

The directed triboelectric experiment indicates the ease of an electron exchange from and to the Sandfish skin

Electric levitation hypothesis

Sandgrain

Electric levitation hypothesis

Sandfish

The effect may work for some seconds, time enough for the sandfish to escape. After that the neutralised charge has to be refilled.

Modern Sand Boarding

The Darkling-Beetle-Effect

Fog catching in

the Namib desert

made by humans

made by nature

and

Darkling beetle of the Namib desert (Stenocara sp.)

Andrew R. Parker and Chris R. Lawrence

10 mHydrophobic burled lowland

Hydrophilic peaks

similar to the Lotus-Effect ®

Fog droplets

Hydrophilic hills

Hydrophobic burls

Fog droplets

Hydrophilic hills

Hydrophobic burls

Condensation

Fog droplets

Hydrophilic hills

Hydrophobic burls

Collected dew

To the mouth of the beetle

Air flo

w

Experiment of Parker and Lawrence

Spray

Fan

Waxen surface

Glass spheres

The Shark-Scale-Effect

Shark scale

The groove structure of the shark scales

0,5 mm

BECHERTs experiments in the Berlin oil-channel

0 2 4 6

0

-2

-4

-6

-8

-10

60o

45o

s

s

s 2

s

WW0

%

s

s 2

*

Sawtooth-Grooves

Trapezoidal-grooves

Rectangular- grooves

Sawtooth-Grooves

Trapezoidal-grooves

Rectangular- grooves

Advertisement of a new swim suit

Mounting a riblet foil on the wing of an airbus

The Water-Strider-Effect

Water strider skating on water

Water strider

Nano-grooves

200 nm20 μmXuefeng Gao & Lei Jiang, Beijing

Robostrider

B. Chan, D. Hu

Development of an artificial water strider

The water spider never gets wet

10 m

The hair of the water spider, a model for a new waterproof suit

Thank for your attention

www.bionik.tu-berlin.de