Nano-Impact
Jonathan P. Rothstein and Mark Tuominen
Mechanical and Industrial Engineering
University of Massachusetts
Amherst, MA, USA
Challenges facing society
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Water
Energy
Health
Sustainable development
Environment
Knowledge
Economy
These are challenges that require interdisciplinary
collaborations to solve!
Global Grand Challenges
2008 NAE Grand Challenges
Top Research Areas of the NNI for 2011
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Fundamental nanoscale phenomena and processes
Nanomaterials
Nanoscale devices and systems
Instrumentation research, metrology, and standards
Nanomanufacturing
Major research facilities and instrumentation
Environment, health and safety
Education and societal dimensions
484M
342M
402M
77M
101M
203M
117M
35M
Making a Better Bulletproof Vest
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A group of researchers at Univ. Del. have impregnated Kevlar vests with a nanoparticle
colloidal suspension resulting in a dramatic improvement in projectile impact.
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The addition of a very small amount of fluid increased performance equivalent to
doubling the number of Kevlar sheets while not changing flexibility of fabric. Why?
Kevlar
Kevlar & Nanoparticle Suspension
Lee, Wetzel and Wagner J. Material Science (2003)
Making a Better Bulletproof Vest
•
A group of researchers at Univ. Del. have impregnated Kevlar vests with a nanoparticle
colloidal suspension resulting in a dramatic improvement in projectile impact.
•
The addition of a very small amount of fluid increased performance equivalent to
doubling the number of Kevlar sheets while not changing flexibility of fabric. Why?
Kevlar
Kevlar & Nanoparticle Suspension
http://www.ccm.udel.edu/STF/images1.html
Nanoparticle Suspensions
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The nanoparticle (d = 13nm)
suspensions are shear thickening –
the faster you shear or stretch them
more viscous (thick) they become.
The dramatic increase in viscosity
dissipates energy as the Kevlar
fibers are pulled out by the impact of
the bullets.
1000
Viscosity [pa.s]
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100
10
1
0.1
1
10
100
-1
Shear Rate [s ]
Increasing
Stretch Rate
1000
Why Size Matters
1mm Particles
100nm Particles
10nm Particles
• For large particles the fluid remains Newtonian like air or water below 30wt%
• Above 30% interactions between and collisions of particles result shear thickening and
elastic effects – particles interact to form large aggregate structures
• For nanoparticles, the effect of nanoparticle addition can be observed at concentrations
closer to 1wt% - why?
• Surface area increases with reduced particle size resulting in enhanced interparticle
interactions
• At same volume fraction smaller particles are packed closer together – electrostatic
interactions are stronger and diffusion is faster so they interact more frequently.
Surface Tension – Keeping Liquids Together
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What is surface tension?
It is an energy per unit area needed to create an interface.
• More interfacial area – more energy
• Liquids want to minimize surface area – form spheres
• Two immiscible liquids will separate – oil in water
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Liquids and solids interact through surface tension, g, and
contact angle, q
From Dr. Seuss’ “Wocket in my Pocket”
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The larger the surface tension the large the force a liquid can exert on a solid
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If water likes a surface, the contact angle is small, q < 90o, and the surface is hydrophilic
If water dislikes a surface, the contact angle is large, q >90o, and the surface is hydrophobic
Water Striders – Living on Top of the Pond
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The smaller you are, the more important surface tension becomes.
Water striders are more dense than water, but use surface tension and nanometer-sized
hydrophobic hairs to support their weight to stay afloat.
Water Strider
Leg
FST
FST
Water
Fg
FST=g * P ~ 0.072N/m*3mm*2*6 ~ 2.6x10-3 N or 2.6x10-4 kg or 260mg
The insect needs to be small!
The Lotus Effect - Superhydrophobic Surfaces
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The leaves of the lotus plant are superhydrophobic – water beads up on the surface of
the plant and moves freely with almost no resistance making the leaves self-cleaning.
Water Drops on a Lotus Leaf
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The surface of the lotus leaf has 10mm sized
bumps which are coated by nanometer sized
waxy crystals – extremely hydrophobic
• Superhydrophobic in fact!
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The water does not wet the entire surface of
the leaf, but only the tops of the roughness.
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Contact angle approaches q = 180o
(the contact angle with air)
Hydrophobic vs. Superhydrophobic
Hydrophobic
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Superhydrophobic
Droplets don’t stick to superhydrophobic surfaces
• Water-based stains don’t adsorb resulting in stain
resistant textiles
• Dirt is picked up by rolling drop as it moves
resulting in a self cleaning surface
• Droplets can be manipulated one at a time on
these surfaces to synthesize or analyze nano or
picoliters of material – nanofluidics
• Snow and ice do not accumulate on these surfaces
Make Your Own Superhydrophobic Surfaces – Part I
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Need: two identical pieces of Teflon, sandpaper (240 grit) and a pipette full of water.
Keep one piece of Teflon smooth.
Lightly sand the second piece of Teflon with a random motion of the sandpaper to
impart micron and nanometer size surface roughness.
Smooth Teflon
Experiment:
• Place a small drop of water on the
smooth Teflon surface.
• Tilt the surface through vertical.
• Does the drop stick or slide?
Sanded Teflon
• Now place a small drop on the sanded
Teflon surface
• Tilt the surface through vertical.
• Can you get the drop to stick?
• Adding micron and nanometer surface
roughness can have a big impact on
how drops adhere to and wet a surface
Make Your Own Superhydrophobic Surfaces – Part II
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In the first experiment we changed surface roughness to make a hydrophobic surface
superhydrophobic here we will change the hydrophobicity of an already rough surface
Need: Regular sand and “Magic Sand” (sand treated to make it hydrophobic)
Need: Two shallow pans/plates, two cups, two spoons and water
Magic Sand
Experiment 1:
• Cover the bottom of one pan with regular sand
and the other with magic sand.
• Place a small drop of water on each.
• What do you observe?
• Agitate/shake the pan.
• Does the drop stick or slide?
Experiment 2:
• Fill two cups with water.
• Pour regular sand into one cup and magic sand
into the other.
• What do you observe?
• Does the magic sand get wet?
• Use a spoon to move sand around. Bring it to
the surface and see what happens!
Using Superhydrophobic Surfaces to Reduce Drag
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We are currently using superhydrophobic surfaces
to develop a passive, inexpensive technique that can
generate drag reduction in both laminar and
turbulent flows.
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This technology could have a significant impact on
applications from microfluidics and nanofluidics to
submarines and surface ships.
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How does it work? The water touches only the tops
of the post and a shear-free air-water interfaces is
supported – effectively reducing the surface area.
d
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Currently capable of reducing drag by over 70% in
both laminar and turbulent flows!
Hierarchical Nanostructures
On Silicon
w
On PDMS
15μm
Can These Surfaces Have a Real Impact?
• Current Energy Resources – Fossil Fuels
• Increasing scarcity
• Increasing cost
• Dangerous to maintain security
• Ocean-going vessels accounted for 72% of all U.S.
imports in 2006
• Technology could be employed to make ships more
efficient or faster
• Friction drag accounts for 90% of total drag
experienced by a slow moving vessel
• A 25% reduction in friction drag on a typical
Suezmax Crude Carrier could…
• Save $5,500 USD / day in #6 fuel oil
• Prevent 43 metric tons of CO2 from entering the
atmosphere each day
60μm
The GENMAR GEORGE T
(Japan Universal Shipbuilding, Tsu shipyard)
Why Size Matters
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To support larger and larger pressures and pressure drops, the spacing of the
roughness on the ultrahydrophobic surfaces must be reduced into the nanoscale.
p  pw  pa 
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4 g cos(  q a )
w
Currently developing processing techniques for large area nanofabrication of
superhydrophobic surfaces with precise patterns of surface roughness.
→ Roll-to-roll nano-imprint lithography – a cutting edge tool.
Coating
Module
R2R NIL
70nm Optical Gratings
Supply
Drive
Module
Imprinting
Module
Receive
Drive
Module
Why Roll-to-Roll Nanoimprint Lithography
Membranes
and Filters
Coating
Module
Supply
Drive
Module
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Roll-to-roll technology will enable fabrication of nanostructured materials and
devices by a simple, rapid, high volume, cost-effective platform.
Current cost of nanofabrication is $25,000/m2
This technology capable of pushing it to $25/m2
• Will help address many of the challenges facing society.
nano.gov
Nanomanufacturing
- the essential link between
laboratory innovations and
nanotechnology products.
Nanomanufacturing
• Processes must work at a commercially
relevant scale
• Cost is a key factor
• Must be reproducible and reliable
• EHS under control
• Nanomanufacturing includes top-down and
bottom-up techniques, and integration of both
• Must form part of a value chain
Nanofabrication & Nanomanufacturing Today
Liddle & Gallatin (NIST), Nanoscale – In press
22
The Cost of Complexity
Logic
Complexity/
Functionality
Storage
Displays
Sensors
Lighting
Photovoltaics
Coatings
$1/m2
Filters
Catalysts
Cost/area
$105/m2
Liddle & Gallatin (NIST), Nanoscale – In press
23
Important Strides in Nano Environmental, Health and Safety
NIOSH: "Approaches to Safe Nanotechnology"
- Emphasizing effective control banding
- Now an ISO standard
NIH: Nano Health Enterprise Initiative
DuPont/EDF: Nano Risk Framework
ACS: Lab Safety Guidelines For Handling Nanomaterials
Lockheed-Martin: Enterprise-wide Procedure for Environmental,
Safety and Health Management of Nanomaterials
and many more efforts
NSF Centers Dedicated to Nano EHS
• University of California Center for the Environmental
Implications of NanoTechnology
• Duke Center for the Environmental Implications of
NanoTechnology (CEINT)
• Rice University Center for Biological and Environmental
Nanotechnology
• Components within other centers
Other Federal EHS Activities
• National Institute for Environmental Health Science
• NIH Nanomaterials Characterization Laboratory
• NIOSH
• EPA
• FDA
Industrial EHS Testing
An open access network for the advancement
of nanomanufacturing R&D and education
• Cooperative activities (real-space)
• Informatics (cyber-space)
Mission: A catalyst -- to support and develop communities
of practice in nanomanufacturing.
www.nanomanufacturing.org
www.internano.org
Nanoinformatics
• Nanotechnology meets Information Technology
• The development of effective mechanisms for collecting,
sharing, visualizing, modeling and analyzing data and
information relevant to the nanoscale science and
engineering community.
• The utilization of information and communication
technologies that help to launch and support efficient
communities of practice.
"The Cathedral and the Bazaar"
(Eric S. Raymond)
The open source movement:
• The power of peer production by a large
group with diverse agendas, expertise and
perspectives
• Yet an appropriate degree of editorial
control (a filter) by an expert body of
authority ensures quality control
"Connect and Develop"
(P&G)
Open Innovation via a distributed network
• Printed Pringles and other examples