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SelfCleaning Surfaces

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Nanobumps are only a few micrometers across and packed very closely ... is a photocatalyst which will oxidize dirt particles when Ultra-Violet rays shines on it ... – PowerPoint PPT presentation

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Title: SelfCleaning Surfaces


1
Self-Cleaning Surfaces
By Stevie Jew, Veena Pathiparampil, Jimmy Teo,
and Jennifer Wong
2
How Nanobumps were Developed
  • Scientists developed nanobumps from lotus leaves
    which are known to repel water very well

3
How 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.

4
Lotus Nanobumps
Scanning electron micrograph image of the surface
of a lotus leaf. Ohio State University
5
Problems 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

6
Titanium 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

7
TiO2 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

8
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9
Redox
  • 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

10
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11
Drawbacks
  • 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

12
Importance
  • 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

13
Photocatalysis 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.
14
Dye, 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.
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