Mechanical and Industrial Engineering University of Massachusetts

Amherst, MA, USA

Nano-Impact

Jonathan P. Rothstein and Mark Tuominen

Challenges facing society

• 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

1. Fundamental nanoscale phenomena and processes

2. Nanomaterials3. Nanoscale devices and systems4. Instrumentation research, metrology, and

standards5. Nanomanufacturing6. Major research facilities and

instrumentation7. Environment, health and safety8. Education and societal dimensions

484M 342M 402M 77M 101M 203M 117M 35M

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?

Lee, Wetzel and Wagner J. Material Science (2003)

Kevlar Kevlar & Nanoparticle Suspension

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

• 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. 0.1 1 10 100 1000

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Shear Rate [s-1]

Increasing Stretch Rate

Why Size Matters

• 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.

1mm Particles100nm Particles

10nm Particles

Surface Tension – Keeping Liquids Together

• 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

• Liquids and solids interact through surface tension, g, and contact angle, q

From Dr. Seuss’ “Wocket in my Pocket”

• The larger the surface tension the large the force a liquid can exert on a solid

• 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

• 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.

Fg

FST FST

Water

Water StriderLeg

FST= g * P ~ 0.072N/m*3mm*2*6 ~ 2.6x10-3 N or 2.6x10-4 kg or 260mgThe insect needs to be small!

The Lotus Effect - Superhydrophobic Surfaces

• 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

• The surface of the lotus leaf has 10mm sized bumps which are coated by nanometer sized waxy crystals – extremely hydrophobic• Superhydrophobic in fact!

• The water does not wet the entire surface of the leaf, but only the tops of the roughness.

• Contact angle approaches q = 180o (the contact angle with air)

Hydrophobic vs. Superhydrophobic

Hydrophobic 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

Superhydrophobic Surface

Dirt

Make Your Own Superhydrophobic Surfaces – Part I

• 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

Sanded Teflon

Experiment:

• Place a small drop of water on the smooth Teflon surface.

• Tilt the surface through vertical.• Does the drop stick or slide?

• 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

• 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 SandExperiment 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• We are currently using superhydrophobic surfaces

to develop a passive, inexpensive technique that can generate drag reduction in both laminar and turbulent flows.

• This technology could have a significant impact on applications from microfluidics and nanofluidics to submarines and surface ships.

• 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.

• Currently capable of reducing drag by over 70% in both laminar and turbulent flows!

w

d

15μm

On PDMS

Hierarchical Nanostructures On Silicon

Can These Surfaces Have a Real Impact?

60μm

• 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

The GENMAR GEORGE T (Japan Universal Shipbuilding, Tsu shipyard)

Why Size Matters

• To support larger and larger pressures and pressure drops, the spacing of the roughness on the ultrahydrophobic surfaces must be reduced into the nanoscale.

• 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.

4 cos( )aw ap p p

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Supply Drive

Module

CoatingModule

ImprintingModule Receive

DriveModule

R2R NIL70nm Optical Gratings

Why Roll-to-Roll Nanoimprint Lithography

• 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.

Supply Drive

Module

CoatingModule

Membranes and Filters

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

22Liddle & Gallatin (NIST), Nanoscale – In press

Nanofabrication & Nanomanufacturing Today

The Cost of Complexity

Complexity/Functionality

Cost/area

Logic

Storage

Coatings

Photovoltaics

Filters

Lighting

Displays

Catalysts

Sensors

$105/m2$1/m2

23Liddle & Gallatin (NIST), Nanoscale – In press

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 InitiativeDuPont/EDF: Nano Risk FrameworkACS: Lab Safety Guidelines For Handling NanomaterialsLockheed-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 centersOther 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