Post on 18-Nov-2014
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Glass Surfaces
Super Hydrophobic Self Cleaning
Lotus-Effect®
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Biomimetics
Technical usage of biological principles
bur
Velcro fastener
Toes of treefrog
Automotive tires
Shark skin
Airbus A320Honey combs
light weight constructions
Lotus leaf
Selfcleaning surfaces
From nature...
Biomimetic surfaces
...to Lab
... to product.
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Lotus-Effekt : Professor Wilhelm Barthlottwww.botanik .uni-bonn.de/biodiv
Lotus-Effect® : Principles
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Lotus-Effect® : Principles
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Lotus-Effect® : Principles
hydrophilic hydrophobic
hydrophilic super hydrophobic
Smooth surface
Micro/Nanostructured surface
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(b)(a)
θσas
σla
σls
Typical Float Glass Surfaceθ ∼ 30ο
Smooth Silane Treated Glass Surface θ ∼ 100ο
Super Hydrophobic Structured Glass Surface θ > 160ο
Lotus-Effect® : Principles
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(a) Smooth hydrophobic surface (b) Superhydrophobic -surface
Lotus-Effect® : Principles
α
On-rolling Angle
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• Application methods:screen printing roll coatingelectrostaticspraying
• Firing of surfacetempering furnace
• Structure is formedin self organizing process
How to form a microstructure?
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• Easy to use
• Low investment necessary
• Fast
• Large surface areas possible
Ferro Lotus Effect Materials
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Nelumbo nucifera(sacred lotus)
...in nature ...artificial
Artificial surface onflat glass
Biomimetic surface structure
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1. Hydrolysis Si(OR)3catalyst ( H+)
+ 3 H2O / - 3 ROHSi(OH)3
(Silanol)
2. Binding tosurface
3. Forming a 2-dim. layer
(glasssurface)
Si(OH)3 +HO SiO
O
SiO
O
- x H2O
Rf
Rf
RfRf
Rf
(
)
n (∆ H)
using fluoroalkyl silanes
Creating a Hydrophobic Surface
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l UV-A stability:no deterioration up to 2000h UV-exposure (wavelength 300 - 425 nm)
l thermal stability:stable up to 300°C
l chemical stability:stable against strong acids and bases up to pH 10
l optical appearance:transparent coating with nm-scale thickness
l UV-A stability:no deterioration up to 2000h UV-exposure (wavelength 300 - 425 nm)
l thermal stability:stable up to 300°C
l chemical stability:stable against strong acids and bases up to pH 10
l optical appearance:transparent coating with nm-scale thickness
Properties of Fluoroalkylsilanes
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Creating a Lotus-Effect® Surface
Application of Lotus-Effect materialscreen printing, roll coating, spraying
1. Firing cycle (formation of micro/nano structure)at approx. 650°C for 3 to 6 minutes
Application of fluoroalkylsilane containing agentspraying, dipping
2. Firing cycle (formation of fluoroorganic coating)at approx. 280°C for 5 to 10 minutes
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Analytical Methods
Mechanical resistanceAbrasion test
Chemical resistanceResistance against acids, bases, detergents
Thermal stabilityBoiling water, water vapor, hot oils
UV-stability and weatheringQUV(B), Kesternich, outdoor weathering
Self CleaningContact Angle, On rolling angle, Transmission
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QUV Testing of Lotus-Effect® Surface
0
20
40
60
80
100
120
140
160
0 500 1000 1500 2000
Time (hour)
Co
nta
ct A
ng
le θ
°
Lotus
Fain
Diamond Seal
Rain X
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Chemical resistivity
After:
2hr in 3 wt% HCl
2hr in 10 wt % citric acid2hr in 0.1 N H2SO4
2hr in 10 wt % NaOH2hr in boiling water
the Lotus-Effect® is stable on glass surfaces
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Accelerated SO2 - atmosphere weathering
0
5
10
0 50 100 150 200 250hours
On
rolli
ng a
ngle
° white frost
clear
blue frost
1 cycle is 24 h with alternating Tempearture 20°C - 60°C, [H2O] and [SO2]
Kesternichtest DIN 51018
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Outdoor-weathering - Washington PA south exposure
0° (horizointal), 45°, 90 ° (vertical)
After a heavy Ice-Rain Storm, 0° samples: covered with a sheet of ice
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Outdoor-weathering - Washington PA south exposure
Ice-Rain Storm 45° samples:Untreated glass surfaces covered with a sheet of ice,Lotus-Effect® surfaces have few large scattered frozen dropletts
Suggests undercooled water has higher viscosity and could partially freeze on Lotus-Effect® surfaces
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Outdoor-weathering - Washington PA south exposure
Ice-Rain Storm 90° samples:Untreated glass surfaces covered with a sheet of ice,Lotus-Effect® surfaces completely free from ice.
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Fungus Study
u Top: Erlenmyer Flask Treated with the Lotus Effect
u Bottom: Untreated Flask
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Lotus-Effect® : Current Efforts
• Transferring Technologyfrom Lab to commercial Applications
• Clear, White frost, and Blue FrostProduct Bulletins available
• Samples available soon
• Establish Industrial Partnerscustomer performance feedback
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Lotus-Effect® Surfaces
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Products: Architectural Flat Glass
Sony-Center, Berlin
Airrail station, Frankfurt Airport
Estimated world market volume (2005):
2,5 billion m2 = 25 billion sqft
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Lotus-Effect® Potential Applications
Indoor applications
Technical glass
Automotive glass
Solar panels
Outdoor lighting
and........
Glass/Metal construction
Optical Sensors/Detectors
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The Lotus-Effect® Team
Dr. Martin Baumann
Dr. Lutz PothDagmar Korbelarz
Dr. Andy Axtell
Dr. Klaus D. Fritsche
Gerhard Tuenker
Dr. George Sakoske
Dr. Stephan Schreiber
Geoff Weinstock
Dr. Ron Harris