Title: SelfCleaning Surfaces
1Self-Cleaning Surfaces
By Stevie Jew, Veena Pathiparampil, Jimmy Teo,
and Jennifer Wong
2How Nanobumps were Developed
- Scientists developed nanobumps from lotus leaves
which are known to repel water very well
3How Nanobumps Work
- Nanobumps are only a few micrometers across and
packed very closely together - Bumps are too small to pierce the surface tension
of a water drop - Bumps are hydrophobic so that water is even more
repelled - This keeps water from sticking to the surface
- Help with car windshields
- It is transparent, and so the glass looks the
same.
4Lotus Nanobumps
Scanning electron micrograph image of the surface
of a lotus leaf. Ohio State University
5Problems and Development
- At close to horizontal angles the water drops do
not slide off because they balance on the
nanobumps - Scientists still need to develop what size and
shape nanobumps are most effective - Nanobump design depends on sliding water drops to
clean off dirt, does not repel dirt directly - Leaves spots and streaks
6Titanium Dioxide
- Window glass would be coated with a thin layer of
titanium dioxide while still molten - Titanium dioxide is a photocatalyst which will
oxidize dirt particles when Ultra-Violet rays
shines on it - Titanium Dioxide is Hydrophilic
- Water will spread out evenly on surface, so it
will sheet off instead of beading up - Water will dry evenly leaving no spots or streaks
7TiO2 is a Photocatalyst
- TiO2 is a semiconductor
- That means that it has an empty conduction band,
but a small band gap (3.2 eV) - Energy from ultraviolet light excites electrons
to the conduction band
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9Redox
- Electrons (e-) in the conduction band can be
donated to dirt molecules (Reduction) - Positively charged holes (h) in the valence band
can accept electrons from dirt molecules
(Oxidation) - Products of the Redox reactions are often H2O and
CO2 which can be washed away - NO2 H2O ? H NO3-
- H CO32- ? H2O CO2
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11Drawbacks
- Depends on Ultra-violet rays from the sun
- Cannot be used on interior glass surfaces such as
mirrors or shower doors - If too much dirt builds up, it can block the
Ultra-violet rays
12Importance
- Spray-on self-cleaning surfaces wear off
- Nanosurfaces would be built into the material and
last the lifetime of the surface - Nanosurfaces can also be used as lubricating
surfaces in microbots which are too small for
liquid lubricants and where friction is a huge
problem
13Photocatalysis Applications of Titanium Dioxide
Ti02.titaniumart.com.lthttp//www.titaniumart.com
/photocatalysis-ti02.htmlgt. Azom.com. CERAM
Research Ltd.lthttp//www.azom.com/details.asp?Art
icleID1179gt. Benedix, Roland, et al.
Application of Titanium DioxidePhotocatalysis to
Create Self-Cleaning Building Materials.lthttp//w
ww.uni-leipzig.de/massivb/institut/lacer/lacer05/
l05_19.pdfgt. clarkpublicutilities.com.lthttp//w
ww.clarkpublicutilities.com/Residential/TheEnergyA
dviser/Archives2004/04_10_17gt.
14Dye, Lee. Abc News. Ohio State.lthttp//abcnews.go
.com/Technology/DyeHard/story?id440893page1gt.
Nano Tsunami.lthttp//www.voyle.net/Future20Tech
nology202005/future202005-0006.htmgt. Ozone
Lite. lthttp//www.ozonelite.com/otheruses.htmlgt.
world changing another world is
here.lthttp//www.worldchanging.com/archives/00084
4.htmlgt.