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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 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 • 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 & Nanoparticle Suspension Kevlar 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 & Nanoparticle Suspension Kevlar 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. Increasing Stretch Rate
Why Size Matters 1mm Particles 100nm 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. 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. Water Strider Leg FST FST Water Fg FST=g * P ~ 0.072N/m*3mm*2*6 ~ 2.6x10-3N or 2.6x10-4kg or 260mg The 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 Dirt Superhydrophobic Surface
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. • 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 Smooth Teflon Sanded Teflon
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 • 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! Magic Sand
d w 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! Hierarchical Nanostructures On Silicon On PDMS 15μm
The GENMAR GEORGE T (Japan Universal Shipbuilding, Tsu shipyard) 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
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. R2R NIL 70nm Optical Gratings Coating Module Supply Drive Module Imprinting Module Receive Drive Module
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. Membranes and Filters Coating Module Supply Drive Module
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 Catalysts Filters Coatings $105/m2 $1/m2 Cost/area 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
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