Macro Micro Nano
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Macro
Micro
Nano
Grains of sand
Red blood cells
DNA (width)
Can see with your eyes
Often requires a microscope
to see
Requires a highly
specialized
microscope, such as
a Scanning Electron
Microscope (SEM),
to see
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Contact Angle
High contact angle
Hydrophobic surface
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Low contact angle
Hydrophilic surface
Making Predictions
1. Examine the slide under the microscope
2. Predict how a drop of water will behave
OR
Rounded
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Flat
SEM of Soot
Int. J. Electrochem. Sci., 6 (2011) 1269 – 1276
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What is nanotechnology?
1. The nanometer is extremely small.
2. At the nanometer scale, many things behave
differently.
3. We can use this new behavior to make new
technologies.
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What is nanotechnology?
Nanotechnology is the understanding and
control of matter 1 to 100 nanometers in size.
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Nanotechnology
Anti-biofouling applications
Scientists coat surfaces
with nanoparticles to
prevent biofouling, seen
here on a submarine.
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Nanotechnology
Biomedical applications
Research is currently underway
that incorporates nano-sized
features on implants to prevent
bacterial growth, and to
encourage the body grow the
correct type of cells on the
implant.
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The Lotus Effect
Lotus leaves and nasturtium
leaves are self-cleaning due to
nano and microscale
structures and a waxy coating.
Together these features create
a superhydrophobic surface.
Close-up of a nasturtium leaf, which exhibits the
Lotus Effect, with a droplet of water
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The Lotus Effect
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Hydrophobic Surfaces
• Water “fearing”
• Repel water
• Non-polar
• Rounded water drop
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Superhydrophobic Surfaces
• VERY water “fearing”
• Non-polar
• Nano-scale surface features
• Water rolls off when surface is held at an
angle
• Water drop is very rounded (contact angle
greater than 150°)
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Hydrophilic Surfaces
•Water “loving”
•Polar
•Flat water drop
•Water drop may absorb into material
•Leaves a streak of water when rolling off
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Water
Covers 70% of the Earth’s surface!
Essential for life
Universal solvent
The only molecule that exists
naturally as a gas, liquid, and solid
Unique properties
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Chemical Formula: H2O
2 Hydrogens covalently bonded to
1 Oxygen
Water Molecule
Properties of Water
1. Polarity
2. Hydrogen Bonding
3. High Surface Tension
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Polarity of Water
Oxygen attracts electrons much more strongly than hydrogen
Partially negative
δ-
δ+
δ+
Partially positive
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Water is polar!
Hydrogen Bonding
Attraction between
water molecules
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Surface Tension of Water
Polarity and Hydrogen Bonding cause water to form a
“skin” of molecules at the surface
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