Lotus Effect

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UML Continuing Education Conference

Glass Surfaces

Super Hydrophobic Self Cleaning

Lotus-Effect®


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.


Lotus-Effekt : Professor Wilhelm Barthlottwww.botanik .uni-bonn.de/biodiv

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



(a) Smooth hydrophobic surface (b) Superhydrophobic -surface


α

On-rolling Angle


• Application methods:screen printing roll coatingelectrostaticspraying

• Firing of surfacetempering furnace

• Structure is formedin self organizing process

How to form a microstructure?


• Easy to use

• Low investment necessary

• Fast

• Large surface areas possible

Ferro Lotus Effect Materials


Nelumbo nucifera(sacred lotus)

...in nature ...artificial

Artificial surface onflat glass

Biomimetic surface structure


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


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


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


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


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


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



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



Ice-Rain Storm 90° samples:Untreated glass surfaces covered with a sheet of ice,Lotus-Effect® surfaces completely free from ice.


Fungus Study

u Top: Erlenmyer Flask Treated with the Lotus Effect

u Bottom: Untreated Flask


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


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


Lotus-Effect® Potential Applications

Indoor applications

Technical glass

Automotive glass

Solar panels

Outdoor lighting

and........

Glass/Metal construction

Optical Sensors/Detectors


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

Lotus Effect

Documents

Transcript of Lotus Effect