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Nanotech Briefs 1 O c t o b e r 2 0 0 3Nanotech Briefs 1 O c t o b e r 2 0 0 3

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Putting the “Tech”in Nanotech

A lmost 45 years ago, physicist Richard Feynman saw a con-nection between biology and small-scale manufacturing.

In 1959, Feynman explained his theory.“A biological system can be exceedingly small. Many of the

cells are very tiny, but they are active — they manufacture sub-stances, they walk around, they wiggle, and they do all kind ofmarvelous things, all on a very small scale. Consider the possibil-ity that we, too, can make a thing very small, which does what wewant — that we can manufacture an object that maneuvers atthat level.”

Feynman was describing nanotechnology, long before theword even existed. Today, that once bizarre theory of manipulat-ing atoms and molecules is one of the fastest-growing technolo-gy areas ever developed.

And technology is why ABPI — the publishers of NASA TechBriefs — is pleased to welcome you to this premier issue of Nan-otech Briefs, the first small-tech publication that focuses on thetechnology of nanotechnology — the best of government andindustry nanotech innovations with real-world applications,developed for the commercial market. Our publication was con-ceived as a conduit for these innovations to reach design engi-neers and engineering managers who are developing tomor-row’s small-tech products today.

In each issue of Nanotech Briefs — which begins as a bimonth-ly publication in January — you’ll also find nanotech govern-ment and industry news in “Small Talk,” the most exciting real-world uses of nanotechnology in our feature story, a profile ofone of the country’s cutting-edge nano research facilities in our“Inside” feature, and an “In Person” interview with a leading nan-otech pioneer. In this issue, we’re pleased to feature a discussionwith Dr. Mihail (Mike) Roco, the key architect of the U.S. NationalNanotechnology Initiative.

We’d like you to use Nanotech Briefs — not just read it. Use it asyour central source of leading-edge government and industrynanotech innovations. Use it to spawn new ideas and solve prob-lems in your design process. And use it to learn more about thestaggering potential of nanotechnology in our daily lives.

Becoming a Nanotech Briefs subscriber is easy. If you’realready a subscriber to the digital (PDF) version of NASA TechBriefs, you’ll automatically receive a free, one-year trial subscrip-tion to Nanotech Briefs in 2004. If you currently receive the printversion of NASA Tech Briefs and choose to either convert to thedigital version or add the digital version to your print subscrip-tion, you’ll also receive a free one-year subscription to NanotechBriefs. Finally, if you’re not a NASA Tech Briefs subscriber, you canget Nanotech Briefs for the introductory subscription price ofonly $49 for a full year. Choose your subscription option atwww.nanotechbriefs.com/subscribe .

Linda L. BellEditor/[email protected]

For a complete list of staff e-mail addresses,visit www.abpi.net



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Nanotech Briefs 2 O c t o b e r 2 0 0 3

TECHNOLOGIES

Electronics10 Nanotube Heterojunctions

Mechanical Systems10 Nanotube Bearing and Spring

Materials11 Organic/Inorganic Hybrid Polymer/Clay

Nanocomposites

12 Low-Temperature Plasma Functionalization of Carbon Nanotubes

13 Nanoparticulate Electrodes Enable Improve Rechargeable Li-ion Batteries

14 Fundamentals of Magnetic Nanomaterials

15 Elastomer Filled With Single-Wall Carbon Nanotubes

16 Modifying Silicates for Better Dispersion in Nanocomposites

Sensors17 Sensor for Monitoring Nanodevice-Fabrication

Plasmas

Manufacturing/Fabrication18 Ordered Nanostructures Made Using Chaperonin

Polypeptides

19 Simple Fabrication of VeryLong Carbon Nanotubes

19 Conductive AdhesivesEnable Assembly of MEMS Chips

20 Growing Aligned CarbonNanotubes for Interconnections in Ics

Biotechnology21 Quantum-Dot-Based Cell Motility, Invasion,

and Metastasis Assays

Software22 Speeding Up the

Internet With MEMS Technology

23 Using Mainstream CAD Software in MEMSand Micro-MechanicalDesign

Test & Measurement25 Nanofluidic Size-Exclusion Chromatograph

26 Scanning Nanomechanics

10

23

19

CONTENTS v o l u m e 1 n u m b e r 1

October 2003

ON THE COVER

Researchers at NASA’s Ames ResearchCenter in California formed this pla-nar array of gold nanoparticles on acarbon film using chaperonin poly-peptides. This and other periodic andotherwise ordered nanostructurescan be fabricated less expensively than using conven-tional lithographic methods. See the tech brief on page18 for details on the technology.(Image courtesy of NASA Ames)

FEATURES

4 Small TalkTech notes and nano news on patents, grants, and industry partnerships.

5 In PersonDr. Mihail Roco, founder of the National Nanotechnology Initiative, discusses its goals,the real potential of nanotechnology, and why it’s worth the risks.

7 Sending Nanotechnology Into SpaceCarbon nanotubes have an important role to play in NASA’s next Hubble Space Telescope servicing mission.

28 Inside:Research at Stanford University’s Nanofabrication Facility includes new innovations in optics, MEMS,biology, chemistry, and electronics.


“For science and engineering departments, whether academic or corporate, with a regular need for solving diffi cult models - and quickly FEMLAB will be a superb investment.”

Ray Girvan, Scientifi c Computing World

Multiphysics Modeling and Simulation

© COPYRIGHT 2003 by COMSOL Inc. All rights reserved. No part of this documentation may be photocopied or reproduced in any form without prior written consent from COMSOL, Inc.FEMLAB is a registered trademark of COMSOL AB. MATLAB is a registered trademark of The MathWorks, Inc. Other product or brand names are trademarks or registered trademarks of their respective holders.

FEMLAB is a finite element based modeling tool with a unique and fl exible equation-based approach. In your FEMLAB models you can include all the inter-acting physics that determine the performance of your processes and devices:

Electromagnetics Structural mechanics Heat and mass transfer Acoustics and vibrations Fluid dynamics

In addition to an easy-to-use graphical user interface, FEMLAB is fully compatible with MATLAB, provid-ing an open and extensible environment with easy access to measured data and hundreds of mathemati-cal functions. Thousands of researchers, engineers, and students at leading universities and corporations worldwide rely on FEMLAB for their modeling and simulation needs.

“For science and engineering departments, whether academic or corporate, with a regular need for solving diffi cult models - and quickly - FEMLAB

“FEMLAB is an extremely versatile tool

for solving all sorts of transport problems

in arbitrary geometries and with a wide

variety of boundary conditions. FEMLAB

is ideal both for course assignments and

research.”

Jim Wilkes, University of Michigan

– brings you FEMLAB

The momentum and mass balances in a cross-fl ow micro-electromechanical systems (MEMS) heat exchanger are coupled to an energy balance using one of the ready-to-use applications in the Chemical Engineering Module. The model calculates the heat exchanger’s temperature distribution and calculates the heat exchanger’s temperature distribution and effi ciency.calculates the heat exchanger’s temperature distribution and calculates the heat exchanger’s temperature distribution and calculates the heat exchanger’s temperature distribution and calculates the heat exchanger’s temperature distribution and calculates the heat exchanger’s temperature distribution and calculates the heat exchanger’s temperature distribution and calculates the heat exchanger’s temperature distribution and calculates the heat exchanger’s temperature distribution and

Visit www.comsol.com/ntb or call +1-781-273-3322 to order your free introductory kit.

The multiphysics capabilities in FEMLAB allows you to freely couple different physical phenomena. In this case, the model couples a structural mecha-nics application with an application for quasi-static electric fi elds in a MEMS-switch. The electric fi eld generates a force that bends the cantilever beam.

Multiphysics Modeling and Simulation

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SMALL TALK

Keithley and Zyvex Join Forces for Nano Solutions

K eithley Instruments (Cleveland, OH), a worldleader in instrumentation for low-level electri-

cal measurements, and Zyvex Corp. (Richardson,TX), a molecular assembly company, have joinedforces to develop new solutions for the nanotechmarketplace. The agreement calls for the companiesto share marketing, sales, and applications engineer-ing resources, and develop new solutions that combine Zyvex’s nanomanipulatorexpertise and Keithley’s ultra-low-level measurement technology.

Keithley’s line of precision electrometers, picoammeters, and nanovoltmeters canmeasure electrical signals generated by nanodevices. Much of the company’s technol-ogy used for characterizing semiconductor devices and test structures at the wafer levelis applicable to nanotechnology.

Zyvex’s family of nanomanipulation systems consists of modular R&D tools that arecompatible with a variety of microscopes and probe stations. Keithley’s Model 4200-SCSsemiconductor characterization system (pictured), when coupled with Zyvex’s S100nanomanipulator, for example, will help engineers developing nanostructures, nanoma-terials, and MEMS.

Visit Keithley at www.keithley.com . Visit Zyvex Corp. at www.zyvex.com .

NSF Grant toStudy Nano’sSocietal Impact

T he National Science Foundation(Arlington, VA) has announced

two new grants of more than $1 mil-lion each to study the societal impli-cations of nanotechnology. Oftenreferred to as a “transformative” tech-nology — one that could change theway we live and work as profoundlyas the automobile — nanotech has“the potential for unintended conse-quences,” according to NSF DirectorRita Colwell. Said Colwell, that’s pre-cisely why “we can’t allow the societalimplications to be an afterthought.The program has to build in a concernfor those implications from the start.”

According to David Baird of the Uni-versity of South Carolina, whichreceived one of the grants, technolo-gies that don’t do that have a way ofcoming to grief later on. “So, how canwe go down a better path with nan-otechnology?” Baird asked. The NSFgrant will allow Baird and his team totackle that question by setting up anongoing dialog with as many points ofview as possible. Just as researchersneed to consider societal implicationsfrom the start, scholars need to under-stand what’s possible in the lab.

The second grant, awarded to theUniversity of California, Los Angeles(UCLA), will help Lynne Zucker andher team study how newly acquiredknowledge about nanotechnologymakes its way from the lab to the mar-ketplace. Zucker explained that this isnot something that happens auto-matically, and many startup compa-nies fail because it’s not done well.One of the products of the UCLAstudy will be an extensive databaseon small startup firms in the nanotecharena, and what factors influencedhow well ideas succeed in the market-place.“It will help us understand howthe knowledge is transmitted, whatfacilitates that transfer, what blocks it,and what works well,” Zucker said.

Visit www.nsf.gov/od/lpa/news/03/pr0389.htm .

Olympus Forms MEMS Division

O lympus Partnership Development Group (PDG) of San Jose, CA, has announcedthat Olympus Optical has formed a new MEMS Technology Division that will unify

all of the company’s previous MEMS activities, including R&D and MEMS foundry ser-vices. The present MEMS foundry will be expanded andhave the capability to handle both existing and devel-oping MEMS technologies on both 4" and 6" wafers,with future capability to handle 8" wafers. The MEMScenter will produce and develop its own products, aswell as provide foundry, R&D, and assembly services toother companies.

Visit www.olympuspartnership.com .

Nanobattery Patent Awarded

T he University of Tulsa announced that chemistry professor Dale Teeters and two for-mer students, Nina Korzhova and Lane Fisher, have been awarded a patent for a

method of making nanobatteries for use in tiny machines.The team has made batteriesthat are so small, that more than 40 of them could be stacked across the width of ahuman hair. They are continuing to make even smaller batteries.

The patented invention is a manufacturing process that can build, charge, and test thenanobatteries.The method includes use of a porous membrane, filling the pores with anelectrolyte, and capping the pores with electrodes. Conventional batteries have twoelectrodes that deliver the charge and an electrolyte through which charged ions move.Each battery packs as much as 3.5 volts.

Funding for Teeters’ research was sponsored by the Department of the Navy’s Officeof Naval Research and the Oklahoma State Regents for Higher Education. Electronicscompanies Sanyo and Panasonic are interested in the battery-making process. The bat-teries can be used to power computers, medical devices, robots, and MEMS.

View the complete patent text at www.uspto.gov . Refer to patent #6,586,133 .


www.keithley.com

www.zyvex.com

www.olympuspartnership.com

www.uspto.gov

www.nsf.gov/od/lpa/news/03/pr0389.htm

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IN PERSON

M ike Roco is the Senior Advisor forNanotechnology at the National Sci-

ence Foundation, and serves as Chair of theSubcommittee on Nanoscale Science,Engineering and Technology (NSET) for theU.S. National Science and TechnologyCouncil. Roco is most notably the founderand key architect of the National Nan-otechnology Initiative (NNI).

Nanotech Briefs: What is the NationalNanotechnology Initiative and whatare its origins?

Dr. Mihail C. Roco: The National Nano-technology Initiative (NNI) is a visionaryresearch and development program thatcoordinates 16 departments and inde-pendent agencies, with a total investmentof about $770 million in fiscal year 2003.The program started formally in fiscal year2001 (October 2000), and was the result ofa bottom-up activity proposing the idea ofdeveloping nanoscience and engineeringthat started in 1996.

At that time, I organized a small groupof researchers and people from govern-ment, and we started to do our home-work in preparing a vision for nanotech-nology. In March 1999, on behalf of thisinteragency group, I proposed at theWhite House the National Nanotech-nology Initiative with a budget of half abillion dollars. At that time, nanotechnol-ogy was not known to anyone in Con-gress or the Administration. We involvedsix major agencies that would place nan-otechnology as a top research priority —the National Science Foundation (NSF),the Department of Defense (DOD), theDepartment of Energy (DOE), NationalAeronautics and Space Administration(NASA), National Institutes of Health(NIH), and the National Institute ofStandards and Technology (NIST).

In January 2000, President Clintonannounced the Initiative. It was the firsttime we had a fundamental-science-driven initiative that was announced by

a president. In the first year, the six agen-cies of the NNI spent about $470 mil-lion. Since then, NNI has increased sig-nificantly, and we now have 16 depart-ments and agencies.

Nanoscale science and engineering arethe wave of scientific discovery and haverelevance in almost all disciplines andareas of the economy. Initially, the topicswere driven by science, but since last year,industry has become a strong supporterand is expected to surpass the expendi-tures made by government next year inresearch and development. Also, statesrealize that nanotech has economicpotential, and in 2002 made a commit-ment for nanotechnology that is morethan half the NNI budget in 2002.

NB: How does the NNI work withindustry to promote and develop nanotechnology?

Dr. Roco: The role of NNI is to createthe foundation to do things that industrycannot do well, and to promote the trans-fer of information to industry and societyat large. NNI will develop visionary proj-ects that only government can dobecause it’s cross-cutting, addresses com-mon issues, and is long-term in its impacton society.

We help industry in many ways.We arelooking to create a workforce for tomor-row for nanotechnology. Second, wewant to develop the knowledge basethat can be applied for different areas ofdevelopment. Third, we want to createan infrastructure. This is an importantissue, because the infrastructure has tobe flexible, applicable in differentdomains, and geographically distrib-uted. The National Science Foundation(NSF) has more than 20 centers fundingnanotechnology, and two networks. Oneis the National Nanofabrication UserNetwork for experiments, and the otheris the Network for Computation of Nan-otechnology. Next year, we’ll expand the

National Nanofabrication User Networkto more than double its size.

NB: What are the NSF’s main focusareas in nanotechnology?

Dr. Roco: NSF in 2002 spent more than$10 million in Small Business InnovationResearch/Small Business TechnologyTransfer (SBIR/STTR) grants for nanotech-nology. In 2002 we spent $22 million fornanomanufacturing, mostly focused onfundamentally new concepts. Just lastmonth, we announced two new centersfor nanomanufacturing and a new centeron instrumentation at the nano scale.

This is a very broad program. In all ofNNI, we have only about 2,000 activeprojects. At NSF, we have about 1,500active projects. We try to cover almost allthe disciplines and areas of activity in abalanced way. We have involvement withindustry, the states, foreign governments,and industrial partners abroad.

NB: How does the United States com-pare with other countries in terms ofnanotechnology development?

Dr. Roco: Nanoscale engineering is avery broad field, and no country hassupremacy in all of the fields. There areseveral areas in which the U.S. is moreadvanced, such as nano/bio, or in materi-als and simulations. We have more organ-ized activity and we have a slightly betterinfrastructure in our physics, chemistry,and genetics departments. Overall, the USprobably has a slight advantage, but it’sdifficult to quantify in each field.

Nanotechnology is slightly differentfrom other technologies. First of all, westarted earlier and felt an external pres-sure. For instance, when the space pro-gram started, it was because of competi-tion with Russia. In nanotechnology, itwas driven by the vision of scientificopportunity.The U.S. did not have a dom-inant advantage. In nanotechnology, the

Dr. Mihail C. RocoFounder and Key Architect, National Nanotechnology Initiative (NNI)


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U.S. does not have the overwhelmingadvantage we have in other technologies.We have to compete harder.

NB: How do you respond to concernsabout the potential societal and envi-ronmental dangers of nanomaterials?

Dr. Roco: Like any emerging technolo-gy, there are questions about societalimplications. And this was addressed fromthe beginning. In October 2000, we organ-ized the first major workshop on societalimplications. Societal implications arequite broad — it implies increasing pro-ductivity, changing healthcare, andexpanding the limits of sustainable devel-opment of the Earth. With existing tech-nologies, we have a limit to the number ofpeople who can live on Earth in a sustain-able way. If we improve that technology,moving to processes with no waste,or witha small amount of materials, this limit willbe extended. Also, like any new technolo-gy, there are social effects like potentialnegative impacts if by accident, materialsare released into the environment. All ofthis has to be taken into account.

We are moving ahead because all theindications so far show that the advan-tages of nanotechnology by far outweighthe potential unexpected consequences.For example, nanoparticles can eventuallytarget cancer cells and visualize illnessesbefore they happen. At the same time,nanoparticles may have effects that arenot yet fully determined. The positiveaspect is that already nanoparticles existall over the Earth. With nanotechnology,we can address current issues that cannotbe solved otherwise.

At the same time, one has to developnanotechnology in a responsible way. Wehave to pay sufficient attention to environ-mental and health issues, as well as to eth-ical and economic issues. It’s interestingthat NNI,because it was developed as a sci-ence project, planned for this from thebeginning. In the first announcement theNSF made in June 2000, we had six majorthemes and one was on environmentalissues and one was societal and education-al issues.

NB: Is the development of nanotech-nology proceeding at an expectedpace, or is practical application stillyears away?

Dr. Roco: It’s been said that nanotech-nology is as complex as the space pro-gram. The main advantage to the spaceprogram was developing knowledgeabout the universe. Moving to nanotech-nology is not only exciting, but willchange the way we live on Earth. Bothbring a lot of excitement. But one thingthat’s different is that in moving to thenano world, you have significant implica-tions for living conditions on Earth and onhealth that are probably broader than anyother technology developed so far. It is arisk sometimes to focus too much on day-to-day activities and not to have a guid-ing, long-term vision that helps to devel-op the programs, find the best invest-ments, and find the best ways to preparethe people.

We are just developing the sciencebase of nanotechnology now. So far, weonly have things that have been devel-oped, I’ll say, by accident. People workingin other fields move to the smaller scaleand discover things. They don’t exactlyknow how they work or why they work. Sowe are still in an empirical phase of nan-otechnology.There will be several phases.The first phase, which we’re already in, isdealing with nanostructures and startingto have systematic control of this. Thenext phase, in three or four years, will bewhen we start to have active nanostruc-tures such as a transistor, an actuator, anactive drug-delivery device. It will beanother several years before we havenano systems.

We don’t want to be too pessimistic ortoo optimistic. We’re moving in this direc-tion — the only question is how far. Whilethe space program had a lot of knowl-edge development, nanotechnology willhave much more, besides an equal inter-est in knowledge and understandingonce we develop the tools, and that willmark a major change in the economy.

One cannot predict exactly the timeinvolved — many developments will bemade by breakthroughs.We cannot makean exact timeline for each event. One has

to keep in mind that basically, we are stillat the beginning of the road. Most of theactivity in nanotechnology is empiricallybased — it’s experimental, stemmingfrom another field prior to nano.

NB: What is the long-term vision fornanotechnology?

Dr. Roco: The vision has three or fourcomponents. It’s not important what’shappening on the “small” end. What’simportant are the new phenomena, thenew processes, the new functions thathappen at the intermediate-length scale.It is not important to work in one field —what’s important is the exchange of tools,methods, architectures, and applicationsamong different disciplines. And it’s

important that you have the ability totransform with a small amount of energyor materials, and to do things that are notpossible at any other scale, and to dothem more economically.

This is robust development — it’s notscience fiction or hype. The develop-ment is real, and is penetrating intomany fields. What I see for this year andnext year is expanding into four newareas: food and agricultural systems,energy conversion and storage, re-generative medicine and nano/biomedicine, and environmental researchand education.

One has to be very careful when read-ing comments from those who are notworking in the field. You find people whosay,“There’s nothing new in nanotechnol-ogy. We’ve been doing this for the past 20years.” These people don’t even knowthat 20 years ago, you had microscopes1,000 times larger, but not to thenanoscale, and you could not manipulateto see the shape of the molecule, tomanipulate them one by one. We’vedeveloped a vision collectively.

Contact Dr. Roco at the National Sci-ence Foundation at [email protected]. Formore information on the NNI, visitwww.nano.gov .

IN PERSON

“Nanotechnology is not science fiction or hype. The development is real,

and is penetrating into many fields.”


www.nano.gov


SendingNanotechnology into

SpaceS ince 1993, the Hubble Space Tele-

scope (HST) has been deliveringsome of the best images of space everseen. The HST has allowed NASA toobserve massive black holes, the birthand death of stars, the origins of gammarays, and much more. As evidenced by thespectacular images taken August 27thwhen Mars made its closest approach toEarth in almost 60,000 years, HST is with-out a doubt an important tool for improv-ing our understanding of the universe.

On its upcoming fourth servicing mis-sion — expected to launch when SpaceShuttle flights resume — HST will receivenew and high-power instruments in thetelescope’s aft shroud section. However,the Space Telescope Imaging Spectro-graph (STIS) is also located in this section,and the heat generated by these newinstruments would wreak havoc withSTIS’s ability to deliver high-quality spaceimages. To address this issue, the fourthservicing mission also will include addinga capillary-pump loop (CPL) technologyto draw the waste heat away from STISand toward the aft shroud’s exterior,where it will be rejected into the colddarkness of space.The challenge with thiscooling solution is how to attach the CPLsystem to the STIS radiator.

The STIS Thermal Interface Kit (STIK)will provide the means to attach the CPLto STIS (see Figure 1). However, STIK’sinterface material must be a good ther-mal conductor that:• can withstand the harsh vacuum of

space,

• provides electrical isolation,• has a low contact pressure (so as not to

damage the STIS instrument),• does not contaminate the spacecraft or

its instruments, and• is abrasion tolerant (astronauts will

have to install STIK around a blind corner).

Compounding this situa-tion is the fact that the STISradiator was never envi -s ioned to be an on-orbitinterface, so no one knowsthe condition of its surface.Although it is safe to say thatSTIS’s surface is likely to bevery uneven, measurementsare impossible to obtain asHST travels above the Earth at18,000 miles per hour.

Finding an effective inter-face material is essential.“Theproblem is that the compliantpolymer materials providingthe flexibility we need are notgood thermal conductors orwould contaminate HST,”explained Dan Powell, a researcher atNASA’s Goddard Space Flight Center inGreenbelt, MD. “And the materials thatare good conductors aren’t going to becompliant enough to mold to STIS’srough surface, creating a good thermalcontact. What we need is a material thatis as flexible as a polymer but as con-ductive as, or better than, copper, andthat can be attached with a low contactpressure.”

The Nanotechnology SolutionThat’s where nanotechnology —

specifically, the carbon nanotube (CNT)— comes in. Although carbon nanotubes(CNTs) were discovered a decade ago,their practical applications are just begin-ning to be explored. Measuring one-bil-

lionth of a meter in diameter, CNTs arecarbon molecules that have been cova-lently bonded in a seamless, hexagonalnetwork architecture (see Figure 2).

CNTs offer highly useful material char-acteristics such as:• Flexible: CNTs offer a linear elasticity of

up to 10%. They also can be manufac-tured with several concentric tubesthat can expand like the sections of apocket telescope.

Figure 1: STIS Thermal Interface Kit (Source: NASA GoddardSpace Flight Center)



• Strong: With a Young’s modulus of morethan 1 terapascal, CNTs offer a strength-to-weight ratio 500 times better thanaluminum, steel, and titanium as well asan order of magnitude improvementover graphite/epoxy.

• Electrically conductive: CNTs, particu-larly multiwalled CNTs, are robustohmic conductors with extremely highcurrent-carr y ing capabi l i t y. Theyremain stable at current densities ashigh as 109 A/cm2, more than threeorders of magnitude higher than cop-per wires.Yet in situations like with HST,electrical conductivity can be eliminat-

ed so as not to pose any shorting orcontamination problems.

• Thermally conductive: Although test-ing is still being done, the theoreticalconductivity of CNTs in the axial direc-tion is 6,000 W/m-K, whereas copper’sconductivity is only about 400 W/m-K.

Seeking an appropriate interfacematerial for the STIK, NASA decided totry to leverage these characteristics and,more importantly, the fact that a CNTinterface would have a low contact pres-sure. Powell and his colleagues are nowworking out the engineering details toput the CNTs into practical application.

Because the timeframe for develop-ing the CNT interface is very short, NASAasked its Ames Research Center in Mof-fett Field, CA, and the Applied PhysicsLaboratory (APL) at Johns Hopkins Uni-versity to create a usable nanoconduc-tor.“Having two labs working simultane-ously helps reduce the risk of failure,”said Powell. “It increases the chancesthat we’ll get what we need for the HSTservicing mission on time.”These collab-orative efforts are just one example ofsome of the benefits yielded by the Nanotech Alliance (see the sidebar onpage 9).

FEATURE

Figure 2: Scanning electron microscope views of 30µm-long vertical carbon nanotube arrays (Source: NASA Ames Research Center)

S ince Goddard is a space flight center, it is continually work-ing to take the scientific breakthroughs discovered at

NASA’s research centers and get them ready for launch.“It’s likea jigsaw puzzle,” explained Goddard’s Dan Powell. “AmesResearch Center provides us with the pieces, and we figure outhow to put them together to make a picture. Maintaining ongo-ing communication between the scientists and the engineershelps ensure that the pieces will fit in the picture NASA is tryingto create.”

In addition to the research related to the Hubble servicingmission, NASA also is exploring other space flight applicationsfor its nanotechnology research. Much of this work is being per-formed jointly with members of the Nanotech Alliance:• Goddard researcher Jeannette Benavides has developed a

new noncatalytic method for manufacturing carbon nanotubes, which might have by-the-ton yields, cost of less than $10 per gram to produce, and could greatlyenhance the feasibility of using CNTs in space as well as otherapplications.

• Using oriented nanocomposite extrusion to produce “design-er” materials — tailoring their properties to the specific appli-cation without changing their constituents — could provide amore reliable alternative to graphite-epoxy composites.

• Filling CNTs with lithium-methane and/or lithium-hydridecould protect space, terrestrial, and even biological systemsfrom energetic neutrons/protons and gamma radiation.

• A software program for finite element analysis with atomic-scale resolution might be used to study a wide range of nanosystems — from theoretical material design to structuralanalysis to designing energetic materials (e.g., rocket propel-lant, car fuel).

• Nanoelectronic, cosmochemistry, and nanoelectrode array bio-chemical sensors could serve as low-power, high-sensitivityelectronic sensors for NASA’s space science, Earth science, andbiological and physical research missions as well as DNA, RNA,and protein sensors for “bioexplorers.”

• A CNT X-ray source has been incorporated into an instrumentfor analyzing the chemistry and mineralogy of solar systemobjects and later could be applied to microelectronics for sur-face analysis for <1kg mass spectrometers, spacecraft steriliza-tion, or in vivo cancer treatment.

Other possibilities for nanotechnology at NASA include ultra-lightweight electrically conductive CNT-based satellite tethers,selectively rechargeable quantum chemical sensing assays, self-actuating radiometer hinges, and long-range self-deployingphased array antennae.

NASA’s Nano Research



Ames and APL are aligning arrays ofCNTs, and optimizing their characteristicsfor the needs of the HST project.“Our firstCNT product will be a 6-square-inch,copper-backed thermal conductor,”explained Dr. Robert Osiander, who isleading APL’s research effort.“On it will beapproximately 4 billion nanotubes stick-ing up about 40-millionths of a meterfrom the copper surface. Think of a laun-dry brush with stiff but somewhat flexiblebristles rising from its wooden base.”

Ames is working on arrays with similarlength and tube density specifications,which were selected to ensure good contact between STIK and STIS. Amesresearchers have established a plasma-enhanced chemical vapor depositionmethod that can grow freestanding CNTarrays on various substrates with densi-ties from 107 to 109 CNTs per square cen-timeter, which fits the requirements ofthis application.

HST researchers are testing the CNTarrays for STIK. By mounting the nanocon-ductor and a compliant pad on a thincopper foil at the end of a mechanicalarm, NASA researchers hope to establishbillions of points of contact with STIS.

Several technical issues must beaddressed before the CNT interface willbe ready for the HST servicing mission.These issues include determining exactlywhat the thermal conductivity of the CNTinterface is and exactly how an astronautwill attach STIK’s interface to STIS. “We stillhave a lot of work to do,” said Ted Swan-son, Goddard’s Assistant Chief for Tech-nology for the Mechanical EngineeringDivision. “We began testing in June, andso far it’s looking promising. The HubbleDevelopment Project Office is very sup-portive and is as excited about this tech-nology application as we are.”

Contact Dan Powell at [email protected].

FEATURE

M uch of the nanotechnologywork that is proceeding for the

space program has come out of theNanotech Alliance (NTA). Currentlycomposed of nearly 20 governmentand academic labs — including NASA,the Applied Physics Laboratory (APL)at Johns Hopkins University, the Uni-versity of Maryland at College Park, theNaval and Army Research Labs, theNational Institute of Standards andTechnology, and many others — theNTA is dedicated to advancing nan-otechnology research. But rather thanfocusing on delivering a tangibleproduct, the NTA members focus onbuilding their relationships to allowthe benefits of collaboration to berealized.

The NTA began simply as informaldiscussions between researchers atNASA Goddard Space Flight Centerand APL.“I had been working with APLfolks on other research,” recalled God-dard’s Dan Powell, who founded theNTA in September 2002. “When werealized we had a mutual interest innanotechnology, it made sense toleverage our current relationship intothat new area.”

Over time, Powell made similar con-tacts within other organizations, build-ing the NTA’s membership with tworepresentatives each from eight labs.“We always have one scientist and oneengineer from each organization forbalance,” said Powell. “The scientistsconsider what’s possible, and the engi-neers focus on what’s practical.”

As the NTA members continued tomeet monthly, they found specific

research areas where their interestsand goals overlapped. In those cases,NTA members would team up to con-duct research jointly. A key benefit ofthis joint research has been the effi-cient use of resources — most ofwhich are provided by the taxpayers.“By knowing who the key players are,what they’re looking at, and wherethings can be combined, you candirect your efforts where they bringthe most value,” Powell said. “There’snot enough money for all of us to beworking alone, so we’d better worktogether.”

And such collaboration has paid off.“We have done a lot to advance NASA’sresearch in nanotechnology for thespace program, and much of thatprogress can be attributed to theNTA,” emphasized Powell.“On average,research efforts take 20 years to getfrom concept to flight. For the Hubblerepair we’re testing now, which was acooperative effort between NASA andAPL, it took two and a half years.”

Now that the NTA has grown tonearly 20 organizations, the group isplanning its first conference forNovember 25, 2003, in Laurel, MD.Attendees, who will be invited fromthe broader nanotech community, willlook at the latest advances in nan-otechnology, taking an applicationsfocus. The emphasis will be on systemdevelopment and the integration ofnanotechnology into those systems.

For more information about the N a n o t e c h A l l i a n c e , v i s i t w w w .nanotech-alliance.org or contact Dan Powell at [email protected] .

The Nanotech Alliance

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MECHANICAL SYSTEMS

ELECTRONICS

C arbon nanotube struc-tures have been de-

signed that enable the cre-ation of nanometer-scalediodes, transistors, and sen-sors. These carbon nan-otubes, containing metal/semiconductor or semicon-ductor/semiconductor junc-tions, may be used to formelectronic devices that are 1to 2 nanometers in eachdimension. Nanoscale de-vices envisioned includeSchottky barriers, quantumwells, and transistors 10,000times smaller in area thanpresent commercial silicondevices.

A novel topological solution thatmatches tubes with different electronicstructures enables the creation of thesejunctions. Carbon nanotubes are synthe-sized to contain pentagon-heptagon

pair defects in their normal hexagonalstructure. The defects change the helici-ty of the nanotube and alter its electron-ic structure. In addition to forming allcarbon heterojunctions, the tubes can

be doped with boron ornitrogen to add charge carri-ers to the semiconductingregion.

Applications for the tech-n o l o g y i n c l u d e m i c r o -switches, micromachines,microsensors, computationelements, high-strengthfibers, smart materials, andother devices that requirehigh thermal conductivity,high mechanical strength,high temperature stability,and high-potential devicedensity.

This research was per-formed by Alex Zettl ofLawrence Berkeley National

Lab. For further information, contact PamSeidenman,Technology Transfer Dept., 510-486-6461, e-mail: [email protected], or visitwww.lbl.gov/tt . Refer to Technology #IB-1181.

Nanotube HeterojunctionsThese carbon nanotubes can be used to form electronic devices.

Ernest Orlando Lawrence Berkeley National Laboratory, U.S. Department of Energy, Berkeley, CA

Researcher Alex Zettl, displaying a model of a Carbon Nanotube, has createdmechanical switches far too small to be seen without the aid of an electronmicroscope.

Nanotube Bearing and SpringMultiwall nanotubes can perform as nanoscale linear bearings and nanosprings.


T hrough controlled and reversible tel-escopic extension, multiwall nan-

otubes have been shown to perform asextremely low-friction nanoscale linearbearings and constant-force nanosprings.Measurements of individual custom-engi-neered nanotubes — performed in situinside a high-resolution transmissionelectron microscope — have explicitlydemonstrated the anticipated van derWaals energy-based retraction force.

These measurements have also placedquantitative limits on the static anddynamic nanotube/nanotube interwallfriction forces, and have shown that the A telescopically extended Multiwall Nanotube.


www.lbl.gov/tt


MATERIALS

nanotubes behave as constant-forcesprings that do not follow Hooke’s law.

On the atomic scale, no wear andfatigue were observed after notingrepeated extension and retraction of telescoping nanotube segments.

This indicates that the new multiwall nanotubes may constitute wear-freesurfaces.

This research was performed by JohnCummings, Alex Zettl, Steven Louie, andMar vin Cohen of Lawrence Berkeley

National Lab. For further information, con-tact Pam Seidenman, Technology TransferDept., 510-486-6461, e-mail: [email protected], orvisit www.lbl.gov/tt . Refer to Technology#IB-1649.

MECHANICAL SYSTEMS

Organic/Inorganic Hybrid Polymer/ClayNanocompositesThe exfoliation and dispersion of clay particles are improved.

NASA’s Langley Research Center, Hampton, Virginia

A novel class of polymer/clay nano-composites has been invented in an

attempt to develop transparent, light-weight, durable materials for a variety ofaerospace applications. As their namesuggests, polymer/clay nanocompositescomprise organic/inorganic hybrid poly-mer matrices containing platelet-shapedclay particles that have sizes of the order ofa few nanometers thick and several hun-dred nanometers long. Partly because oftheir high aspect ratios and high surfaceareas, the clay particles, if properly dis-persed in the polymer matrix at a loading

level of 1 to 5 weight percent, impart uni-que combinations of physical and chemicalproperties that make these nanocompos-ites attractive for making films and coatingsfor a variety of industrial applications. Rela-tive to the unmodified polymer, the poly-mer/clay nanocomposites may exhibitimprovements in strength, modulus, andtoughness; tear, radiation, and fire resist-ance; and lower thermal expansion andpermeability to gases while retaining ahigh degree of optical transparency.

The clay particles of interest occurnaturally as layered silicates. In order

to fully realize the benefits of a poly-mer/clay nanocomposite, it is necessarythat the clay particles become fully exfo-liated (delaminated) and uniformly dis-persed in the polymer matrix. Con-comitantly, it is necessary to maintainthe exfoliation, counteracting a tenden-cy, observed in prior formulations ofpolymer/clay nanocomposites, for dis-persions of exfoliated clay particles tocollapse back into stacked layers uponthermal treatment. One reason for thedifficulty in achieving and maintainingexfoliation and uniform dispersion is the

Organic Precursor Inorganic Precursor

Inorganic Precursor

Hybrid-Clay Solution

Hybrid Sol-Gel Solution Clay Solution

Solvent Clay Solvent

High-Shear Mixing Sonication



This Flow Diagram shows the major steps of a process for making a film of an organic/inorganic hybrid polymer/clay nanocomposite.


www.lbl.gov/tt


MATERIALS

Low-Temperature Plasma Functionalization of Carbon NanotubesThis process is dry, clean, and relatively simple.

NASA’s Ames Research Center, Moffett Field, California

A low-temperature plasma processhas been devised for attaching spec-

ified molecular groups to carbon nan-otubes in order to impart desired chemi-cal and/or physical properties to the nan-otubes for specific applications. Unlikecarbon-nanotube-functionalizationprocesses reported heretofore, thisprocess does not involve the use of wetchemicals, does not involve exposure ofthe nanotubes to high temperatures, andgenerates very little chemical residue. Inaddition, this process can be carried outin a relatively simple apparatus and canreadily be scaled up to mass production.

The apparatus used in this processincludes two vacuum chambers, denotedthe target chamber and the precursorchamber. A plasma of the chemical precursor of the molecular groups to be deposited is generated in the precur-sor chamber. The plasma flows from

the precursor chamber to the targetchamber, wherein the carbon nanotubesto be functionalized are mounted on asubstrate.

The process is best described by use ofan example of functionalizing carbonnanotubes with hydrogen atoms.The pre-cursor chamber is backfilled with high-purity (99.9999 percent or greater) H2 gas,optionally mixed with an inert carrier gas(N2, Ne, or Ar), to a total gas pressurebetween 0.1 and 1 mm of Hg (betweenabout 13 and about 130 Pa). The gas isirradiated with microwaves, thereby gen-erating free electrons and a partially ion-ized gas that includes free radicals (in par-ticular, monatomic hydrogen). Instead of amicrowave source, a DC, non-microwave-radio-frequency, inductive-discharge, orelectron-cyclotron-resonance source canalso be used to generate the plasma. Thetemperature of the free electrons is typi-

cally of the order of a few electron volts (1eV = 11,604 K). The temperature of thepartially ionized gas typically lies in theapproximate range from 350 to 1,000 K.

The two chambers are connected by acurved tube or plug made of polytetraflu-oroethylene or other suitable material.Typically, the tube or plug has an innerdiameter of about 1 mm, an outer diame-ter of between 5 and 25 mm, and a lengthbetween 5 and 25 mm. The substrateholding the carbon nanotubes is posi-tioned to face directly into the plasmaflowing into the target chamber throughthe hole in the tube or plug.

The tube or plug is curved to eliminatea direct line of sight between the interi-ors of the chambers in order to preventultraviolet light originating in the pre-cursor chamber from reaching the car-bon nanotubes. This is necessary for thefollowing reasons: Some ultraviolet radi-

incompatibility between the silicate par-ticle surfaces (which are hydrophilic)and the polymer matrix (which ishydrophobic). The present inventionaddresses these issues.

The figure depicts a process for mak-ing a polymer/clay nanocomposite filmaccording to the invention. In one of twobranches of the first step, a hybrid organ-ic/inorganic matrix resin in a sol-gel formis prepared. The organic precursor of thehybrid is a compound or oligomer thatcontains both a cross-linkable functionalgroup (e.g., phenylethynyl) and analkoxysilane group. The inorganic pre-cursor of the hybrid is also an alkoxysi-lane. Both precursors are mixed with asolvent to form the sol-gel matrix resin.In the other branch of the first step, a claysolution is prepared by initially dispers-ing layered clay particles in the same sol-vent as that used to form the sol-gelmatrix resin. To achieve intercalation of

the solvent into the stacked layers, themixture is subjected to high-shear mix-ing and to ultrasound. Suitable clays toprovide compatibility to the organicpolymer include chemically modifiedorganophilic cation-exchanged smectitetype clays and synthetic clays havinghydroxyl functional groups on the edgesand/or elsewhere on the surfaces of theparticles.

In the second step of the process, theclay solution is added to the hybrid sol-gelsolution and the resulting mixture subject-ed to high-shear mixing and ultrasound.The hydroxyl groups of the organic/inor-ganic hybrid react with hydroxyl groups onthe surfaces and the edges of the exfoliatedclay particles, forming covalent and/orhydrogen bonds that enhance exfoliationin the presence of high shear.

The third step involves a film castingprocess. For example, to make an unori-ented film, one begins by simply casting

the solution onto a glass plate or othersuitable clean, dry surface. The solution isallowed to dry to a tack-free film in ambi-ent, desiccated air, then further dried andcured in flowing heated air. During thisthermal treatment, the remaining silanolgroups of the hybrid undergo condensa-tion reactions, forming a molecular net-work that prevents the reunion of theexfoliated particles into stacked layers. Inaddition, the organic matrix can be con-solidated with further crosslinkingamong the cross-linkable functionalgroups during thermal cure. It may bepossible to prepare oriented films andfibers by using shear, drawing, and fiberspinning processes.

This work was done by Cheol Park (NRC),John W. Connell, and Joseph G. Smith, Jr., ofNASA’s Langley Research Center. For moreinformation, contact the Langley Commer-cial Technology Office at (757) 864-3936.Refer to LAR-16216



MATERIALS

ation is generated in the undesired butunavoidable recombination of some ofthe monatomic hydrogen into H2 mole-cules. This radiation is capable of break-ing the C–H bonds in hydrogenatedmaterials, including hydrogenated car-

bon nanotubes. Other ultraviolet radia-tion generated in the precursor chambermay be capable of breaking C–C bondsin the nanotubes.

There is no need to maintain the tem-perature in the target chamber at any par-

ticular value in order to achieve function-alization. Experiments have shown thatcarbon nanotubes can be functionalizedwith hydrogen to the point of saturationin a process time of about 30 seconds, ator below room temperature. It is also pos-sible to functionalize carbon nanotubeswith molecular groups other than hydro-gen. For example, by choosing a suitableprecursor, one could attach halogen oralkali metal atoms or low-molecularweight hydrocarbons.

This work was done by Bishun Khare ofSETI Institute and M. Meyyappan of NASA’sAmes Research Center. For further informa-tion, please contact M. Meyyappan at (650) 604-2616 or E-mail: [email protected].

Inquiries concerning rights for the com-mercial use of this invention should beaddressed to the Patent Counsel, AmesResearch Center, (650) 604-5104. Refer toARC-14661-1

Curved Tube or Plug

SubstrateCarbon

Nanotubes

VacuumPump

MicrowaveSource

Percursor Chamber

Sourceof

Hydrogen

A Hydrogen Plasma is generated in the precursor chamber and flows into the target chamber,where hydrogen atoms become chemically bonded to the carbon nanotubes.

Nanoparticulate Electrodes Enable ImprovedRechargeable Li-ion Batteries NEI Corporation, Piscataway, New Jersey

T he unique structural features ofnanostructured powders lead to en-

hanced diffusion of Li-ions, therebydelivering high power density, alongwith a long cycle life and high charge/discharge rate capability. The surfaceand internal structures of nanomaterialsare often very different from that of con-ventional coarse particles.This has sever-al ramifications, including the fact thatthe primary particle or grain sizes are atleast an order of magnitude smaller thanthose used in conventional electrodematerials. This implies that a battery canbe fully charged or discharged at a muchfaster rate, without compromising thecapacity.

Nanostructured electrode materialsfor rechargeable Li-ion batteries, brand-ed as Nanomyte™, may reduce the waitassociated with recharging laptops andcamcorders from hours to tens of min-utes. Intrinsically low-cost materials,when used in the nanostructured form, Figure 1. Schematic of an Electrochemical Test Assembly.



lead to higher capacity compared totheir coarse-grained counterparts.

Quick charge/discharge capabilities areneeded in applications such as uninter-ruptible power supplies, power tools, andhybrid electric vehicle batteries. Nanopar-ticles of certain compositions and struc-tures can potentially increase the energydensity of Li-ion batteries; this is becauseof the additional sites available on thesurface of the nanoparticles in addition tothe intercalating sites — only the latterbeing available in micron-sized particles.Also, the volume distortion associatedwith intercalation is relatively small innanomaterials. As a result, the reversibleintercalation reaction can occur severaltimes without any “damage” to the elec-trode material. This results in a long cyclelife; i.e. the initial capacity can be main-tained for a large number of cycles.

Another unique feature of nanoparti-cles is the ability to use alternative inter-

calating ions — such as magnesium —instead of lithium. The advantage is thatmagnesium is significantly less expen-sive than lithium, and the resultantrechargeable device has the capability ofdelivering still higher power densities,along with good energy densities.

Over the past few years, NEI has beenworking closely with a number of groupsin academia and industry to developnanostructured materials for use in avariety of rechargeable “rocking-chair”devices, the rechargeable Li-ion batterybeing one of them. For example, under aNASA-sponsored program, NEI is devel-oping a nanostructured and layeredlithium manganese oxide-based materi-al, LiMnO2. To date, an initial dischargecapacity of ~250 mA/g has beenachieved. The capacity drops somewhatat higher discharge rates, but there ispractically no capacity loss over 100cycles. This material has the potential to

surpass the energy density achieved inspinel LiMn2O4 as well as in LiCoO2, whichis the standard cathode material.

On the anode side, NEI has develop-ed nanostructured lithium titanate(Li4Ti5O12) using a novel low-costmethod. The ultrafine material displaysnear-theoretical capacity at moderatecharge rates (1 hour charge) , and >90% capacity at exceptionally highcharge rates (20-minute charge). Othercathode compositions, based on phos-phates, are also in advanced stages ofdevelopment.

In summary, nanomaterials presentunprecedented opportunities for achiev-ing the performance goals of severalapplications at competitive cost.

This article was written by Amit Singhal,Chief Scientist, and Ganesh Skandan, CEO,at NEI Corporation. For more information,visit www.neicorporation.com or call(732) 868-1906.

MATERIALS

Fundamentals of Magnetic NanomaterialsMagnetic interactions between nanomaterials can be characterized using this method.

Materials Science Department, Brookhaven National Laboratory, U.S. Department of Energy

L ocal magnetic interactions betweenferromagnetic and antiferromag-

netic nanocrystallites strongly dependupon the chemical and topographicalnature of the inter face, and theexchange-bias effect is a sensitive meas-ure of these interactions. Additionally,the geometry of the interfacial regionmay also affect the magnetism.To exam-ine the effects of the geometry of theferromagnetic/antiferromagnetic inter-facial region upon the intrinsic andextrinsic magnetic properties of anexchange-biased system, a 13-nm-thickf i lm of interspersed Ni and NiOnanocrystallites was produced usingreactive dual ion-beam deposition.

X-ray diffraction, Rutherford backscat-tering spectroscopy, and SQUID magne-tization and susceptibility measure-ments were used to characterize thesample. Results indicate that the film hasan overall composition of 75 at. % Ni and25 at. % O with average grain sizes of 6nm (Ni) and 7 nm (NiO). A measured TN =

510 K for the NiO nanocrystallites isslightly reduced from the bulk value (525K); however TC = 580 K for the Ni isseverely depressed compared to thebulk value (627 K), possibly due toexchange effects or chemical inhomo-geneities.

A strong temperature and measuringfield dependence for both the coercivityand exchange field strength is present.The coercivity rapidly decreases withincreasing temperature in large measur-ing fields (5 T) and remains essentiallyconstant with small measuring fields (0.05T). Most notably, the exchange field variesfrom positive to negative with rising tem-perature in a strong measuring field butremains positive with rising temperaturein smaller measuring fields.

In addition to their technologicalattributes, magnetic nanocompositematerials exhibit interesting, non-intuitivephysical properties such as an apparentincreased Curie temperature of the lower-TC constituent and anomalous high-tem-

perature coercivities. To investigate theorigin of these phenomena quantificationof the internal strain state of the individ-ual phases in melt-quenched Nd2Fe14B +α-Fe nanocomposites was undertaken.Synchrotron x-ray diffraction studies wereperformed at the National SynchrotronLight Source, and the data was analyzedwithin the framework of a modifiedWilliamson-Hall method. It was deter-mined that the constituent Nd2Fe14Bgrains are largely strain-free, but the α-Fecomponent exhibited significant stress(~1 GPa) with an associated strain ofapproximately 0.1%.

The results of this study helped toconfirm that the enhanced TC of Nd2Fe14Bwas likely an exchange- and not stress-induced effect as well as provide a basisfor the marginal remanence enhance-ment and anomalous elevated-tempera-ture coercivities found in these nano-composites.

Fe layers of 100 nm and 200 nm thick-ness evaporated onto slices of Gd5Si1.5Ge2.5


www.neicorporation.com


are found to increase the dc initial sus-ceptibility and shift the metamagnetictransition to low field. These effects leadto an enhancement of the magne-tocaloric effect around the entropy peaktemperature. At the current time, themechanism underlying the observed

phenomena is not clear; candidatemechanisms are a magnetostatic effect,an exchange interaction between theferromagnetic Fe layer and the first fewnanometers of the Gd5Si1.5Ge2.5 and a mechanical “clamping” effect from the layer.

This work was done by Dr. Laura J.Henderson Lewis of the Center for Func-tional Nanomaterials at Brookhaven Na-tional Laboratory. Visit www.cfn.bnl.gov/research/nanoassemblies/ for more in-formation. Contact Dr. Lewis at [email protected].

MATERIALS

Elastomer Filled With Single-Wall CarbonNanotubesStrength and stiffness increase with SWNT content.

NASA’s Lyndon B. Johnson Space Center, Houston,Texas

E xperiments have shown that com-posites of a silicone elastomer with

single-wall carbon nanotubes (SWNTs)are significantly stronger and stiffer thanis the unfilled elastomer. The largestrengthening and stiffening effectobserved in these experiments stands incontrast to the much smaller strengthen-ing effect observed in related prior effortsto reinforce epoxies with SWNTs and toreinforce a variety of polymers with multi-ple-wall carbon nanotubes (MWNTs). Therelative largeness of the effect in the case

of the silicone-elastomer/SWNT compos-ites appears to be attributable to (1) a bet-ter match between the ductility of thefibers and the elasticity of the matrix and(2) the greater tensile strengths of SWNTs,relative to MWNTs.

For the experiments, several compos-ites were formulated by mixing variousproportions of SWNTs and other fillingmaterials into uncured RTV-560, which isa silicone adhesive commonly used inaerospace applications. Specimens of astandard “dog-bone” size and shape for

tensile testing were made by casting theuncured elastomer/filler mixtures intomolds, curing the elastomer, then press-ing the specimens from a “cookie-cut-ter” die.

The results of tensile tests of the speci-mens showed that small percentages ofSWNT filler led to large increases in stiff-ness and tensile strength, and that theseincreases were greater than those afford-ed by other fillers. For example, the incor-poration of SWNTs in a proportion of 1percent increased the tensile strength by

Control Specimen:Unfilled Elastomer

1% SICWhiskers

1% UnpurifiedSWNT,

Manually Mixed

5% GroundCarbon Black

5% SICWhiskers

10% SICWhiskers

5% UnpurifiedSWNT,

Manually Mixed

Composite Specimens Containing Fillers as Noted

10% UnpurifiedSWNT,

Mechanically Mixed

10% GroundCarbon Black

0.89 0.85

1.56

0.931.21

2.05

2.57

5.89

1.00

7

6

5

4

3

2

1

0

Mo

du

lus

of E

last

icit

y, k

psi

The Stiffness of a Silicone Elastomer filled with several different kinds and proportions of reinforcing materials was measured in standard tensile tests.


www.cfn.bnl.gov/research/nanoassemblies/


MATERIALS

Modifying Silicates for Better Dispersion in NanocompositesProcessability and final material properties are improved.

NASA’s John H. Glenn Research Center, Cleveland, Ohio

44 percent and the modulus of elasticity(see figure) by 75 percent. However, therelative magnitudes of the increasesdecreased with increasing nanotube per-centages because more nanotubes madethe elastomer/nanotube composites

more brittle. At an SWNT content of 10percent, the tensile strength and modulusof elasticity were 125 percent and 562percent, respectively, greater than thecorresponding values for the unfilledelastomer.

This work was done by Bradley S. Filesand Craig R. Forest of NASA’s Johnson SpaceCenter. For further information, access theTechnical Support Package (TSP) free on-line at www.techbriefs.com/tsp under theMaterials category. Refer to MSC-23301

A n improved chemical modificationhas been developed to enhance the

dispersion of layered silicate particles inthe formulation of a polymer/silicatenanocomposite material. The modifica-tion involves, among other things, the co-exchange of an alkyl ammonium ion anda monoprotonated diamine with interlay-er cations of the silicate. The net overalleffects of the improved chemical modifi-cation are to improve processability ofthe nanocomposite and maximize thebenefits of dispersing the silicate particlesinto the polymer.

Some background discussion is neces-sary to give meaning to a description ofthis development. Polymer/silicate nano-composites are also denoted polymer/clay composites because the silicate par-ticles in them are typically derived from

clay particles. Particles of clay compriselayers of silicate platelets separated bygaps called “galleries.” The platelet thick-ness is 1 nm.The length varies from 30 nmto 1 µm, depending on the silicate. Inorder to fully realize the benefits of poly-mer/silicate nanocomposites, it is neces-sary to ensure that the platelets becomedispersed in the polymer matrices. Properdispersion can impart physical and chem-ical properties that make nanocompos-ites attractive for a variety of applications.

In order to achieve nanometer-leveldispersion of a layered silicate into a poly-mer matrix, it is typically necessary tomodify the interlayer silicate surfaces byattaching organic functional groups. Thismodification can be achieved easily byion exchange between the interlayermetal cations found naturally in the sili-

cate and protonated organic cations —typically protonated amines. Long-chainalkyl ammonium ions are commonly chosen as the ion-exchange materialsbecause they effectively lower the surfaceenergies of the silicates and ease theincorporation of organic monomers orpolymers into the silicate galleries. Thiscompletes the background discussion.

In the present improved modification ofthe interlayer silicate surfaces, the co-ionexchange strengthens the polymer/silicate interface and ensures irreversibleseparation of the silicate layers.One way inwhich it does this is to essentially tetherone amine of each diamine molecule to asilicate surface, leaving the second aminefree for reaction with monomers duringthe synthesis of a polymer. In addition, theincorporation of alkyl ammonium ions

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SENSORS

The term “plasma process diagnostics”(PPD) refers to a spectroscopic tech-

nique and sensing hardware that havebeen proposed for monitoring plasmaprocesses used to fabricate electronicdevices that feature sizes as small as sever-al nanometers. Nanometer dimensions arecharacteristic of the quantum level ofminiaturization, where single impurityatoms or molecules can drastically changethe local properties of the nanostructures.Such changes may be purposely used innanoscale design but may also be extreme-ly damaging or cause improper operationof the fabricated devices. Determination oftemperature and densities of reactantsnear the developing features is important,since the structural synthesis is affected bycharacteristics of the local microenviron-ment. Consequently, sensors capable ofnonintrusive monitoring with high sensitiv-ity and high resolution are essential for real-time atomistic control of reaction kineticsand minimizing trace contamination inplasma processes used to fabricate elec-tronic nanodevices. Such process-monitor-ing sensors are required to be compact,multiparametric, and immune to the harshenvironments of processing plasmas. PPDis intended to satisfy these requirements.

The specific technique used to imple-ment plasma diagnostics with a PPD sensorwould be an advanced version of

continuous-wave cavity-ringdown spec-troscopy (CW-CRDS) capable of profilingspectral line broadenings in order to deriveboth Doppler and Stark components.CRDSis based on measurements of the rate ofabsorption of laser light in an optical res-onator.The ultimate sensitivity results froma very long absorption path length withinthe cavity and immunity to variations inincident laser intensity. The proposed ver-sion of this technique would involve theuse of multiplexing tunable laser diodesand an actively modulated high-reflectivityoptical resonator,thus offering a synergisticcombination of simplicity, compactness,high sensitivity, and high resolution.

The multiplexing capabilities of diodelasers could be utilized to make the PPDsensor a single, simple, compact, and inex-pensive tool for the acquisition of multi-parametric data. A PPD sensor would becapable of continuous measurement ofsuch physical parameters as gas tempera-ture, gas velocity, electron number densi-ty, and absolute densities of reactingchemical species. A laser beam can beeasily adjusted to analyze the immediatevicinity of the growing nanostructures (orfeatures etched down) in real time. Theabsorption enhancement in an opticalcavity would afford the sensitivity neededfor measurement of the temperature anddensities of species at concentrations sig-

nificantly lower than measurable by othernonintrusive techniques.

It is anticipated that fully developed PPDsensors would enable simultaneous meas-urement of local temperature and determi-nation of plasma species responsible forthe synthesis and functionalization of nan-odevices. These sensors would also enabletracking the pathways and origins of dam-aging contaminants, thereby providingfeedback for adjustment of processes tooptimize them and reduce contamination.The PPD sensors should also be useful foroptimization of conventional microelec-tronics manufacturing plasma processes.

Going beyond plasma processes forfabrication of electronic devices, PPD sen-sors could be used for monitoring ofatoms, molecules, ions, radicals, clusters,and particles in a variety of other settings,including outer space. Because of theirhigh sensitivity, such sensors could alsoprove useful for detecting traces of illegaldrugs and explosives.

This work was done by AlexanderBol’shakov while he held a National ResearchCouncil associateship award at NASA’sAmes Research Center.

Inquiries concerning rights for the com-mercial use of this invention should beaddressed to the Patent Counsel, AmesResearch Center, (650) 604-5104. Refer toARC-15084-1.

Sensor for Monitoring Nanodevice-Fabrication PlasmasTemperature and trace amounts of chemical species could be measured in situ.


MATERIALS

into the galleries at low concentrationhelps to keep low the melt viscosity of theoligomer formed during synthesis of thepolymer and associated processing — aconsideration that is particularly impor-tant in the case of a highly cross-linked,thermosetting polymer. Because of thechemical bonding between the surface-modifying amines and the monomers,

even when the alkyl ammonium ionsbecome degraded at high processingtemperature, the silicate layers do notaggregate and, hence, nanometer-leveldispersion is maintained.

This work was done by Sandi Campbellof NASA’s Glenn Research Center. For fur-ther information, access the TechnicalSupport Package (TSP) free on-line at

www.techbriefs.com/tsp under theMaterials category.

Inquiries concerning rights for the com-mercial use of this invention should beaddressed to NASA Glenn Research Center,Commercial Technology Office, Attn: SteveFedor, Mail Stop 4–8, 21000 BrookparkRoad, Cleveland, Ohio 44135. Refer to LEW-17339.




MANUFACTURING/FABRICATION

Ordered Nanostructures Made UsingChaperonin PolypeptidesThis method exploits the ability of chaperonins to assemble into complex structures.


A recently invented method of fab-ricating periodic or otherwise

ordered nanostructures involves the useof chaperonin polypeptides. The methodis intended to serve as a potentiallysuperior and less expensive alternativeto conventional lithographic methodsfor use in the patterning steps of the fab-rication of diverse objects characterizedby features of the order of nanometers.Typical examples of such objects includearrays of quantum dots that would serveas the functional building blocks offuture advanced electronic and photonicdevices.

A chaperonin is a double-ring proteinstructure having a molecular weight ofabout 60±5 kilodaltons. In nature, chap-eronins are ubiquitous, essential, subcel-lular structures. Each natural chaperoninmolecule comprises 14, 16, or 18 proteinsubunits, arranged as two stacked ringsapproximately 16 to 18 nm tall byapproximately 15 to 17 nm wide, theexact dimensions depending on thebiological species in which it originates.The natural role of chaperonins isunknown, but they are believed to aid inthe correct folding of other proteins, byenclosing unfolded proteins and pre-

venting nonspecific aggregation duringassembly.

What makes chaperonins useful for thepurpose of the present method is thatunder the proper conditions, chaperoninrings assemble themselves into higher-order structures. This method exploitssuch higher-order structures to definenanoscale devices. The higher-orderstructures are tailored partly by choice ofchemical and physical conditions forassembly and partly by using chaper-onins that have been mutated. The muta-tions are made by established biochemi-cal techniques.

The assembly of chaperonin polypep-tides into such structures as rings, tubes,filaments, and sheets (two-dimensionalcrystals) can be regulated chemically.Rings, tubes, and filaments of some chap-eronin polypeptides can, for example,function as nanovessels if they are able toabsorb, retain, protect, and release gasesor chemical reagents, including reagentsof medical or pharmaceutical interest.Chemical reagents can be bound in, orreleased from, such structures under suit-able controlled conditions.

In an example of a contemplated appli-cation, a two-dimensional crystal of chap-

eronin polypeptides would be formed ona surface of an inorganic substrate andused to form a planar array of nanoparti-cles or quantum dots. Through geneticengineering of the organisms used tomanufacture the chaperonins, specificsites on the chaperonin molecules and,thus, on the two-dimensional crystals canbe chemically modified to react in a spe-cific manner so as to favor the depositionof the material of the desired nanoparti-cles or quantum dots. A mutation thatintroduces a cysteine residue at thedesired sites on a chaperonin of Sul-folobus shibatae was used to form planararrays of gold nanoparticles (see figure).

This work was done Jonathan Trent,Robert McMillan, and Chad Paavola ofNASA’s Ames Research Center; RakeshMogul of University of California, SantaCruz; and Hiromi Kagawa of SETI Institute.For further information, access http://www.ipt.arc.nasa.gov/trent.html andhttp://amesnews.arc.nasa.gov/audio/bionanosound/bionano9.html.

Inquiries concerning rights for the com-mercial use of this invention should beaddressed to the Patent Counsel, AmesResearch Center, (650) 604-5104. Refer toARC-14744.

This Planar Array of Gold Nanoparticles was formed on a carbon film by the method summarized in the text.


www.ipt.arc.nasa.gov/trent.html

http://amesnews.arc.nasa.gov/audio/bionanosound/bionano9.html



S ome MEMS (MicroElectroMechanicalSystem) chip designs are simply too

fragile for traditional solder flip chipassembly. Examples would include MOEM(MicroOptoElectroMechanical) mirrorarrays with delicate balance beams, andfluidic and DNA analysis chips that cannottolerate exposure to either high tempera-tures or aggressive cleaning procedures

to remove flux residues. For sensitivecomponents such as these, electricallyconductive, silver-filled adhesives may bethe only available option for first-levelchip assembly.

Conductive epoxies typically are curedat temperatures ranging between only70-150°C compared with 235-265°C forreflow-soldering and require no post-

cleaning procedure. They are also surpris-ingly good electrical conductors whencompared to solder. A typical flip chipconnection made with conductive epoxyranges from 6-10 milliohms, compared toan equivalently sized solder connectionwith 3-5 milliohms resistance.

Automated dispensing equipment isoften employed when depositing non-

Conductive Adhesives Enable Assembly of MEMS ChipsFlip chip mounting enables fragile MEMS devices to be assembled without damaging process steps.

Polymer Assembly Technology, Inc., Billerica, Massachusetts

Simple Fabrication of Very Long Carbon NanotubesThis inexpensive process yields very long carbon nanotubes with narrow-diameter distribution.

Ernest Orlando Lawrence Berkeley Laboratory, U.S. Department of Energy, Berkeley, CA

A simple, inexpensive, high-yield pro-cess requiring no special apparatus

has been devised for fabrication of high-quality, very long carbon nanotubes withnarrow-diameter distribution. This me-thod improves upon existing arc dis-charge, laser ablation, and chemicalvapor deposition (CVD) methods, all ofwhich have various problems, includinglack of control of catalyst/precursorratios in starting materials and products;the need for fabrication of specializedapparatus; limited area coverage of nan-otube mats (which translates into a lowyield); and the need for overly high tem-peratures for fabrication.

The new process successfully fabricateslarge-area, freestanding films of very longcarbon nanotubes by heating a transitionmetal complexed alkyne with aryl and/oralkyl substituents.The heating of the tran-sition metal complex can be completed in0.5 to 3.0 hours at 550 to 700°C in a sealedvessel under partial pressure of argon orhelium (in contrast to typical chemicalvapor deposition, which involves a flow oforganic compound over a transitionmetal catalyst).

The heating results in high yields of car-bon nanotubes as freestanding films ornanotube mats, which can be simply lift-ed off the inside of the vessel. Coverage ofareas more than 4 cm2 has been achievedfrom about 30 mg of the starting com-plex. Compared to other processes, theyields are essentially quantitative.

The removal of the transition metalfrom the films is a simple process,achieved by immersing the film in aque-ous hydrochloric acid and filtering out thedissolved metal. This allows for greaterpurity in the final carbon nanotube yield.

Applications for the technologyinclude field emitters, high-strengthfibers, strong radiation shields, energy-absorbing materials, nanoscale catalyticbeds, nanocircuits, nanoscale transistors,frictionless nanobearings, and electro-mechanical and optoelectronic devices.

This research was performed by K.P. Voll-hardt and V.S. Iyer of Lawrence BerkeleyNational Lab. For further information, con-tact Pam Seidenman, Technology TransferDept., 510-486-6461, e-mail: [email protected], orvisit www.lbl.gov/tt . Refer to Technology#IB-1719.

TEM (200 keV, JEOL 200 CX microscope)images of Carbon Nanotubes.


www.lbl.gov/tt


conductive “underfill” epoxies under-neath flip chip mounted devices toincrease chip interconnect reliability, butis less effective when applying conduc-tive epoxy bumps. Unlike their non-con-ductive counterparts, the silver-filledepoxies are more viscous and prone toparticle agglomeration, which can clogsmaller dispensing needles. Dot size uni-formity can therefore vary considerablyand is presently limited to an approxi-mately 125 µm diameter. A more practicalapproach, especially for high pin-countapplications when pitch dimensionsbetween flip chip bumps are small andwhen processing whole wafers, is thestencil printing process.

An array of stencil-printed epoxybumps can be seen in Figure 1, whichwas taken from a section of a 3D MOEMmirror array substrate. This unit requiredaccurate placement of the mirror cells inthree axes. The Z-height needed to becontrolled by a soft placement tech-

nique onto a tightly packed pattern ofconductive epoxy bumps that wouldmerge into a contiguous conductive thinfilm.The MEMS mounting surface includ-ed regions with very thin, fragile wallsseparating adjacent mirror cells. In thesesections, only a single row of bumps wasdeposited to prevent any epoxy fromspreading into the cell’s interior regionand potentially interfering with the mir-ror’s movement.

In this application, over 40,000 bumpswere required per doublet-cell. The sten-cil-printing process required only a fewseconds to perform this process step,yielding a near-perfect array of uniformconductive bumps. Attempting todeposit this pattern using an automaticdispenser would have consumed far toomuch time, and the epoxy would havebegun to set up before the pattern couldbe deposited and transferred into theplacement machine. Many low-tempera-ture-curing (<100°C) conductive epoxieshave a short “pot-life” and begin to hard-en within a few hours, placing a restrictionon the process cycle time.

The stencil-printing process also canbe adapted for multiple prints using dif-ferent epoxy materials on the same sur-face. Another application, for example,required a MEMS device be attached toan Au-coated silicon substrate atop anintegral 5-µm-high insulator. First, a pat-tern of 5-µm-high dielectric epoxy bumpswas stencil-printed and cured, followedby a separate print depositing an outer

pattern of conductive epoxy bumps toelectrically and mechanically secure theMEMS device to the substrate surface(Figure 2). The required 5-µm-high insula-tor bumps were achieved by determin-ing the right combination of stencilaperture and printing parameters for theparticular viscosity of the dielectricepoxy used.The conductive epoxy in thiscase was a b-staged, solvent-based, ther-moplastic material to which the MEMSdevice was subsequently thermo-com-pression bonded.

As wafer scale packaging techniquesare considered for MEMS devices, theadvantages of using stencil-printed poly-mer materials should not be overlooked.

This article was written by James Clay-ton, President of Polymer Assembly Technol-ogy, Inc. For further information, visit www.polymerassemblytech.com, or call 1-978-667-0071.


Figure 2: MEMS Device Mounting Substratewith stencil-printed, conductive, and dielectricepoxy patterns.

Figure 1: MOEM Test Substrate illustratingconductive epoxy spreading pattern.

Growing Aligned Carbon Nanotubes for Interconnections in ICsCarbon nanotubes are embedded in silica with their tips exposed as contacts.


A process for growing multiwalled car-bon nanotubes anchored at speci-

fied locations and aligned along specifieddirections has been invented. Typically,one would grow a number of the nan-otubes oriented perpendicularly to a sili-con integrated-circuit (IC) substrate, start-ing from (and anchored on) patterned cat-

alytic spots on the substrate. Such arraysof perpendicular carbon nanotubes couldbe used as electrical interconnectionsbetween levels of multilevel ICs.

The process (see Figure 1) begins withthe formation of a layer, a few hundrednanometers thick, of a compatible electri-cally insulating material (e.g., SiOx or SiyNz)

on the silicon substrate. A patterned filmof a suitable electrical conductor (Al, Mo,Cr, Ti, Ta, Pt, Ir, or doped Si), having a thick-ness between 1 nm and 2 µm, is deposit-ed on the insulating layer to form the ICconductor pattern. Next, a catalytic mate-rial (usually, Ni, Fe, or Co) is deposited to athickness between 1 and 30 nm on the


www.polymerassemblytech.com


spots from which it is desired to growcarbon nanotubes.

The carbon nanotubes are grown byplasma-enhanced chemical vapor depo-sition (PECVD). Unlike the matted andtangled carbon nanotubes grown bythermal CVD, the carbon nanotubesgrown by PECVD are perpendicular andfreestanding because an electric fieldperpendicular to the substrate is used inPECVD. Next, the free space between thecarbon nanotubes is filled with SiO2 bymeans of CVD from tetraethylorthosili-cate (TEOS), thereby forming an array ofcarbon nanotubes embedded in SiO2.Chemical mechanical polishing (CMP) isthen performed to remove excess SiO2

and form a flat-top surface in which theouter ends of the carbon nanotubes areexposed. Optionally, depending on theapplication, metal lines to connect select-ed ends of carbon nanotubes may bedeposited on the top surface.

The left part of Figure 2 is a scanningelectron micrograph (SEM) of carbon nan-

otubes grown, as described above, on cat-alytic spots of about 100 nm diameterpatterned by electron-beam lithography.These and other nanotubes were foundto have lengths ranging from 2 to 10 µmand diameters ranging from 30 to 200nm, the exact values of length dependingon growth times and conditions and theexact values of diameter depending onthe diameters and thicknesses of the cat-alyst spots. The right part of Figure 2 is anSEM of an embedded array of carbonnanotubes after CMP.

This work was done by Jun Li, Qi Ye, AlanCassell, Hou Tee Ng, Ramsey Stevens, JieHan, and M. Meyyappan of NASA’s AmesResearch Center. For further information,access the Technical Support Package (TSP)free on-line at www.techbriefs.com/tspunder the Manufacturing category.

Inquiries concerning rights for the com-mercial use of this invention should beaddressed to the Patent Counsel, AmesResearch Center, (650) 604-5104. Refer toARC-15042-1.

BIOTECHNOLOGY


Deposition of Metal

Deposition and Patterning of Catalyst

PECVDCarbon Nanotubes

Substrate With Top Insulating Layer

TEOSCVD

CMP

Deposition of Metal on Tips of Nanotubes

Figure 1. A Bottom-Up Approach is followedin growing carbon nanotubes, embeddingthem in a silica matrix, exposing their tips, andusing the exposed tips as electrical contacts.

Figure 2. These Electron Micrographs, both taken at an angle of 45°, show specimens of arrays ofcarbon nanotubes at two different stages of processing. (The scale bar on the left is 5 µm, the oneon the right is 0.2 mm.)

R esearchers have discovered a pow-erful tool for studying cell mobility

and migration — behaviors that are

responsible for metastases of primarycancers. The researchers compared themotions of cancerous and healthy

human breast cells, as well as severalother cell types, as they migrated acrossa layer of colloidal semiconductor

Quantum-Dot-Based Cell Motility, Invasion,and Metastasis AssaysA new technique enables cell motility and migration studies.





BIOTECHNOLOGY

nanocrystals. As they move, they engulfthe quantum dots and leave behind aphagokinetic track that yields informa-tion about the health of the cells.

M igrat ion of ce l l s and their metastatic potentialare well known to be cor-related.

Colloidal quantum dotsare robust and efficientlight emitters that havebeen used for static biolog-ical labeling. They are supe-rior to organic dyes, whichfade quickly and perturbthe assayed cells. Thesenanocrystals are sponta-neously ingested by a widevar iet y of ce l l s whi leremaining fully lumines-cent, enabling researchersto examine live cells overextended time periods, andto quantify changes inresponse to various molec-ular manipulations.

This new technique is less labor-intensive than the Boyden Chamberinvasion assay method. It does notrequire killing the cells, and it enables

real-time variation of external condi-tions and analyses of cellular responses.It also overcomes the marker problemsencountered in the original phagokinet-ic tracking methods.

This method can be coupled to in-formation about chemical signals andallows a wide variety of tissue culturesubstrates to be used, including growthon all extracellular matrix substances.

The improved cell motility studies andrapid assaying of metastatic potentialenabled by this quantum dot methodwill provide improved diagnostics andenhanced information for cancer drugdevelopment.

This research was performed by CarolynLarabell, Paul Alivisatos, W.J. Parak, R.Boudreau, M. LeGros, D. Gerion, D. Zanchet,C.M. Micheel, and S.C. Williams ofLawrence Berkeley National Lab. For fur-ther information, contact Pam Seiden-man, Technology Transfer Dept., 510-486-6461, e-mail: [email protected], or visitwww.lbl.gov/tt . Refer to Technology #IB-1755.

Engulfment of Nanocrystals reveals migratory paths of breasttumor cells. A wide variety of mammalian cells engulf quantumdots when migrating. This migration is correlated to the cell’smetastatic potential. After 24 hours, dark clearings in thenanocrystal layer are observed around motile tumor cells.

A s Internet traffic continues to grow,so does consumer demand for

increased bandwidth to support data-intensive multimedia applications. Inresponse, telecommunications companiesare expanding and upgrading their fiber-optic networks. A key to improving per-formance is the use of new optical switch-es, which can redirect signals amongthousands of different ports. Opticalswitch systems offer improvements overalternate methods in speed, data capacity,data management, and cost.

SiWave, a supplier of optical switchingcomponents and subsystems, is develop-ing an optical switch using microelectro-mechanical systems (MEMS) technology.

MEMS are micromachines the size of agrain of salt or the eye of a needle thatintegrate mechanical elements, sensors,actuators, and electronics on a commonsilicon substrate. MEMS devices are fabri-cated using photolithographic-basedsemiconductor processes that selectivelyetch away parts of the silicon wafer oradd new layers to form the variousdevices. The unique characteristics ofMEMS devices allow the manufacture ofextremely small optical switching prod-ucts that provide new levels of capability,reliability, and complexity at a relativelylow cost.

The telecommunications industry hasstringent shock specifications for all

components — even if they can fit onthe head of a pin. According to Telcordiastandards, all components must be ableto survive a 500-g, 1-millisecond, 1/2-sine pulse. Equivalent to dropping a rigidobject six feet onto concrete, this stan-dard ensures that components will with-stand shocks they might see in the field;for example, during installation or whena technician thrusts a card into an adja-cent rack. For geometrically complexdevices such as a MEMS optical switch,the specification becomes an importantdesign consideration.

SiWave used ALGOR finite elementanalysis-based simulation software in thedevelopment of this product to predict

Speeding Up the Internet With MEMS TechnologySimulation software is used to design a MEMS optical switch.

ALGOR, Inc., Pittsburgh, Pennsylvania and SiWave, Arcadia, California

SOFTWARE


www.lbl.gov/tt


SOFTWARE

the performance and durability of thedevice. The 1-mm optical switch mirrorwas modeled in SolidWorks and InCADtechnology was used to seamlessly cap-ture the model for use in ALGOR. Aftercreating an automatic mesh, it wasrefined in Superdraw, ALGOR’s finite ele-ment modeling tool.

Anticipating that the optical switchmight be susceptible to shock, a built-in100-Hz frequency isolation system within

the MEMS device’s packaging wasplanned that would provide about 40%damping. The optical switch within theisolation system would actually experi-ence a peak acceleration of 163 g’s. It wasthis attenuated shock value that wasinput into the simulation.

Because critical resonance frequencieswere high compared to the duration ofthe shock, an inertial acceleration methodwas considered as a good way to approx-

imate the behavior of the mirror undershock conditions. This method requiredno special constraints, only a standardgravity input and a time history curve.Although the Telcordia standards call for a1/2-sine pulse, the isolation system affectsthe shape as well as the magnitude of theshock load — resulting in a sine-shapedload — so that the optical switch actuallywill get shaken in two directions withinjust a few milliseconds.

In addition to the shock load, pub-lished, orthotropic material properties forthe silicon and silicon compounds thatcomprise the optical switch were input.Also, the surfaces of the part that weremost likely to experience possible contactwere examined, and restricted contactpairs were defined.

Both von Mises stress and displace-ment results were examined. One concernfor this component is the orientation intowhich it displaces. If the part were to con-tact the packaging, it could get stuck. Themirror’s motion could not result in inter-ference with surrounding components.Another concern was that the devicemight drum itself against its base, so itwas important to know whether contactoccurred and the stresses that resultedfrom it.

This work was done by Robert Calvet ofSiWave, Inc. To read this complete story,visit http://SiWavetechnology.ALGOR.com . For more information on ALGOR, visitwww.ALGOR.com .

ALGOR Mechanical Event Simulation (MES) software was used to calculate Stress and Displace-ment Results over time for an applied shock load on the MEMS optical switch. The image shows adisplay of von Mises stress results.

U ntil recently, microelectromechani-cal systems (MEMS) and micro-

mechanical design and production weremore often research-oriented activitiesthat took place in university labs, thancommercially viable manufacturingenterprises. The design and manufactur-ing tools used for MEMS and micro-mechanical design were highly special-

ized, and very few engineers knew how toaccomplish micro-design without devel-oping manufacturing techniques andenabling technologies as part of thedesign process. Much of this work wasdone using 2D layouts to represent con-figurations of the separate layers of sili-con that are deposited sequentially tocreate a conventional MEMS component.

One development that is helping tofacilitate the widespread use of MEMSand micro-design techniques is theinclusion of MEMS-specific functionalityin mainstream 3D computer-aideddesign (CAD) applications. The ability touse a familiar tool and design environ-ment for designs ranging from MEMSand micro devices to larger assemblies

Using Mainstream CAD Software in MEMS and Micro-Mechanical DesignSolid modeling tools can simplify the complexity of the MEMS design process.

SolidWorks Corporation, Concord, Massachusetts


http://SiWavetechnology.ALGOR.com

www.ALGOR.com


SOFTWARE

and components eliminates the time,effort, and cost involved with learningspecialized tools.

The typical sequence for designing aMEMS device is to begin with a model ofthe component created out of multiplesemiconductor layers. Designers thenproduce photo masks — 2D layouts foreach layer that match each specificcross-section configuration to drivemanufacturing. A significant challengein MEMS design arises in working withphoto masks for several cross-sectionsof a solid model at the micron and sub-micron level for a device that will bepackaged in a much larger assembly.Without MEMS-specific CAD functionali-ty, designers must move back and forthin their CAD systems between differentdimensional scales, from microns to mil-limeters to meters; are unable to trulyvisualize the complete assembly; andcannot take advantage of basic solidmodeling features such as parametricassociative design.

Solid modeling systems simplify thecomplexity of the process by providingcapabilities that specifically addressMEMS design functions. For example,SolidWorks® 3D CAD software enables abroad geometric range, which allowsdesigners to work on the same assemblyat the micron level all the way up to many

meters. Engineers can zoom into theMEMS detail and zoom out to the largerassembly, providing full 3D visualizationof both the MEMS component and itspackaging.The software also automatical-ly cross-sections the MEMS componentand creates fully associative photo masksfor each layer. As the design is modified

and refined, changes propagate to allassociated design documents, includingcomponents, assemblies, detail, andphoto-mask drawings. Sub-micron feature definition, collision/interferencedetection of components, and the cre-ation of feature patterns and patterns ofpatterns are capabilities that are also use-ful for MEMS design.

Another important benefit in usingmainstream CAD for MEMS design is theability to conduct structural, thermal,electromagnetic, and fluid flow analysesdirectly on the solid model. Finite ele-ment analysis (FEA) is extremely impor-tant for predicting the behavior and per-formance of a MEMS component ormicro device before producing costlyprototypes.

The introduction of MEMS-specificcapabilities in mainstream design toolsis helping to pave the way to greater useof micro technology. These tools willhelp companies facing miniaturizationchallenges to break new ground; toinnovate products, devices, and micro-manufacturing technologies; and tobroaden the use of MEMS systems for avariety of applications.

This article was written by Ilya Mirman,Vice President of Marketing, SolidWorksCorp. Visit www.solidworks.com formore information.

Figure 1. This Automated Packaging Cell was designed with SolidWorks software, which enablesengineers to design the MEMS device, output the photo mask, design the packaging, and put ittogether in a single software package.

Figure 2. Finite Element Analysis, such as the stress analysis shown here, is important for predicting the behavior and performance of a MEMS component before producing costly prototypes.


www.solidworks.com


E fforts are under way to develop ananofluidic size-exclusion chro-

matograph (SEC), which would be acompact, robust, lightweight instru-ment for separating molecules of inter-est according to their sizes and measur-ing their relative abundances in smallsamples. About as large as a deck ofplaying cards, the nanofluidic SECwould serve, in effect, as a “laboratoryon a chip” that would perform the func-tions of a much larger, conventional,bench-top SEC and ancillary equipment,while consuming much less power andmuch smaller quantities of reagent andsample materials. Its compactness andlow power demand would render itattractive for field applications in which,typically, it would be used to identifyand quantitate a broad range of polarand nonpolar organic compounds insoil, ice, and water samples.

Size-exclusion chromatography is aspecial case of high-performance liquidchromatography. In a conventional SEC,

a sample plug is driven by pressurealong a column packed with silica orpolymer beads that contain uniformnanopores. The interstices between, andthe pores in, the beads collectively con-stitute a size-exclusion network. Mole-cules follow different paths through thesize-exclusion network, such that char-acteristic elution times can be related tosizes of molecules: basically, smallermolecules reach the downstream end ofthe column after the larger ones dobecause the smaller ones enter minorpores and stay there for a while, where-as the larger ones do not enter thepores. The volume accessible to mole-cules gradually diminishes as their sizeincreases. All molecules bigger than apore size elute together. For most sub-stances, the elution times and sizes ofmolecules can be correlated directlywith molecular weights. Hence, bymeasuring the flux of molecules arrivingat the downstream end as a function of time, one can obtain a liquid mass

spectrum for the molecules present in a sample over a broad range of molecularweights.

The developmental nanofluidic SEC isbased on the same size-separation prin-ciple as that of a conventional SEC. How-ever, instead of a packed macroscopiccolumn containing porous beads, thenanofluidic SEC would contain a size-exclusion network in a miniature col-umn in the form of a microscopic chan-nel containing nanometer-scale fea-tures (see figure). More specifically, thenanometer-scale features in the channelwould be sized, shaped, and positionedto define a matrix of micron-width sub-channels topped with a gap of varyingthickness of the order of tens ofnanometers. The miniature columnwould be fabricated by establishedtechniques now used to produce inte-grated circuits (ICs) and microelectro-mechanical systems (MEMS). One ormore device(s) to detect moleculescould be integrated onto the column


Inlet

Outlet

Channel

Nanoscale Size-ExclusionSubnetwork

10 µm

1 mm

Flow

Nanofluidic Size-Exclusion ChromatographThis device would perform the functions of a much larger instrument.

NASA’s Jet Propulsion Laboratory, Pasadena, California

TEST & MEASUREMENT

A Size-Separation Network in a Miniature Channel on a chip would contain nanoscale features. The channel and features would be formed as onepiece in a chip by use of IC and MEMS fabrication techniques.



TEST & MEASUREMENT

T he invention of the scanning tun-neling microscope (STM) and atom-

ic force microscope (AFM) in the 1980shas led to rapid commercialization ofmicroscopes that image surfaces withatomic resolution. As a result, materialsanalyses capabilities at the nano scalehave expanded enormously and nowinclude magnetic, dielectric, tribologi-cal, electrochemical, thermal, andmechanical properties.

However, despite the many advancesin commercially available instrumenta-tion, dynamic mechanical analysis atthis scale has been an elusive goal. Toresolve this problem, we have devel-oped a hybrid nanoindentation systemcapable of measuring quantitativelydynamic materials properties. The out-put of this instrument also can be in theform of an image or map of mechanicalresponse or property (e.g., stiffness,modulus).

High-resolution mapping of mechani-cal properties is possible through theuse of a hybrid nanoindenter that com-bines depth-sensing nanoindentationwith an AFM. This combination enablesquantitative nanomechanical proper-ties analyses with nanometer-scalepositioning and topographical map-ping. These scanning and positioningcapabilities allow investigations ofmaterials and structures (e.g., compos-ites, nanostructured materials, litho-graphic patterns, or microelectro-mechanical systems (MEMS)) that havefeatures below the optical limit.

In an indentation experiment, mecha-nical properties are evaluated using arigid probe of well-defined shape (e.g., apyramid or sphere) to elastically or plastically deform a sample while moni-

toring the load and displacementresponse. We have improved the sensi-tivity of the hybrid nanoindenter byintroducing a small sinusoidal compo-nent to the indentation force anddetecting the displacement signal witha lock-in amplifier.The result is a dynam-

ic measurement of contact stiffness thatis related to both the contact size andelastic properties of the contactingmaterials.

Two significant capabilities arise fromthese dynamic stiffness measurements.First, by scanning the sample under theoscillating probe at low loads (elastical-ly), a two-dimensional map of thedynamic stiffness of the sample can beobtained. Second, by varying the fre-quency of the oscillations, we can inves-tigate dynamic mechanical propertiesinherent in many polymers and bioma-terials. Figure 1 is a schematic of theinstrument.

Figure 2(a) shows a 10mm x 10mmimage mapping the elastic (storage)modulus of a carbon fiber-epoxy com-posite. Contrast in the image, as well asthe rendered height, correspond direct-ly to modulus with lighter regions hav-ing higher modulus. Figure 2(b) shows across section through the center of theimage of the elastic modulus. The imageshows that the center of the carbonfiber has a lower modulus than theperiphery, while the epoxy has a sub-stantially lower modulus than the fiber.

The elastic modulus values obtainedduring the modulus mapping experi-ment were consistent with measuredvalues from standard indentation exper-iments. More importantly, the low loadsused during modulus mapping mini-mized the contact area between theprobe and sample, thereby increasingthe lateral resolution of the technique.

Scanning NanomechanicsA hybrid nanoindentation instrument is capable of measuring dynamic materials properties.

Naval Research Laboratory, Chemistry Division, U.S. Department of Defense, Washington, DC

Figure 1. The Hybrid Scanning Nanoindenter.The load-displacement response of a probeattached to a movable plate is actuated electro-statically to apply force; the displacementresponse is monitored by capacitive techniques.Sample x-y positioning and scanning areaccomplished through a piezo-tube scanner.

chip at the downstream end. Thesedevices could be based, for example, onelectrochemical (in particular, ampero-metric) and laser-induced-fluorescencedetection techniques.

This work was done by Sabrina Feld-man, Danielle Svehla, Frank Grunthaner,Jason Feldman, and P. Shakkottai of Cal-tech for NASA’s Jet Propulsion Laboratory.

For further information, access the Techni-cal Support Package (TSP) free on-line atwww.techbriefs.com/tsp under the Physi-cal Sciences category.

In accordance with Public Law 96-517,the contractor has elected to retain title to this invention. Inquiries concerningrights for its commercial use should beaddressed to

Intellectual Assets OfficeJPLMail Stop 202-2334800 Oak Grove DrivePasadena, CA 91109-8099(818) 354-2240E-mail: [email protected] to NPO-30499.




TEST & MEASUREMENT

Stiffness images can be acquired overa range of frequencies up to ~250 Hz,allowing investigation of dynamicmechanical properties of viscoelasticmaterials. Figure 3(a) and (b) shows twocontact stiffness images of a cross sec-tion of a layered polystyrene (PS) sam-ple, with alternating low (PS1) and high(PS2) molecular weights. The lighterregions in the images correspond tohigher contact stiffness. The two imageswere taken from the same region of thesample while oscillating the probe at105 and 200 Hz, respectively. At 200 Hz,the image contrast is reversed, indicat-ing a strong frequency-dependentresponse of the two PS materials withinthis frequency range.

The image contrast reversal reflects achange in contact stiffness caused bythe frequency-dependent dissipativeproperties of the two polymers. Figure

3(c) plots the dynamic compliance(1/stiffness) of the nanoindenter probein contact with the two polymers as afunction of frequency. This plot shows

that the stiffness of PS1 should be lowerthan PS2 at 105 Hz, but higher than PS2at 200 Hz. Because the compliance max-ima (and equivalent stiffness minima) ofthe polymers occurs near 100 Hz for PS1and near 200 Hz for PS2, dynamic imag-ing at these two frequencies results in astiffness contrast reversal due to thechange in relative compliance betweenthe polymers.

This new scanning nanomechanicstechnique is capable of mapping elasticand visco-elastic response, and is anideal tool for multiphase materials, com-posites, polymers, and nanostructures.

This work was done by S.A. Syed Asif ofHysitron, Inc. and R.J. Colton and K.J. Wahlof the Chemistry Division of the NavalResearch Laboratory. Visit www.nrl.navy.mil/content.php?P=02REVIEW155.

Figure 3. Stiffness Images of alternating layers of polystyrene (PS) of two molecular weights at (a)105 Hz and (b) 200 Hz. The contrast is due to frequency-dependent mechanical response of thepolymers.The probe-sample response as a function of frequency shown in (c) is consistent with thestiffness image.

Figure 2. A two-dimensional Map of the Elastic Modulus (a) of a carbon fiber-epoxy compositematerial. Brighter regions correspond to higher modulus. (b) Cross-section line scan through thecenter of the image shows the storage modulus in the epoxy and the modulus gradient at the cen-ter of the fiber.

(a) (b)

(a) (b) (c)

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www.nrl.navy.mil/content.php?P=02REVIEW155



INSIDE:

Stanford Nanofabrication Facility

T he Stanford Nanofabrication Facility(SNF) at Stanford University in Califor-

nia is directed by Professor Yoshio Nishi,and supports research in areas such asoptics, MEMS, biology, chemistry, andprocess characterization and fabricationof electronics devices. SNF also uses microand nanofabrication technologies in non-traditional research applications.

Hands-on access to SNF is provided tolab members; remote use also is availablefor well-defined projects that are per-formed by the lab’s staff. Remote users aremembers who do not come to SNF to dotheir own nanofabrication processing.Rather, SNF staff performs the processing.A variety of Web-based tools are availablethat allow remotely located researchersto view and inspect their nanofabricationprocess via Webcams, microscope cams,and automated downloads for still micro-scope images.

SNF also participates in the MEMSExchange program, administered by theCorporation for National Research Initia-tives. The MEMS Exchange is a network offabrication facilities that provides MEMSprocess and design capabilities. SNF usersinclude researchers from industrial com-panies and non-Stanford universities, aswell as individual users.

The SNF was spawned from the Inte-grated Circuit Fabrication Facility, whichbegan on the Stanford campus in themid-1960s. The design and fabrication ofMEMS devices has been a major compo-nent of the facility since its beginning,with much of its early support stemmingfrom the medical systems area. Thisresulted in work in the areas of image sen-sors and image processing, accelerome-ters, and implantable electronics. Work indevice and process modeling began inthe mid-1970s, and resulted in the devel-opment of an array of device and processsimulators. The facility was upgraded inthe early 1980s to support larger chips,and then upgraded again in 1986.

Research AreasRecent research at SNF covers a wide

variety of nanotech and MEMS applica-tions, from integrated bio-fluorescence

sensors and micromachined sensors for biological measurements, to design-ing and fabricating piezoresistive pressure sensors using carbon nan-otubes, and integrated circuit thermalmanagement.• Integrated Bio-Fluorescence Sensor

— The need for small, portable biosen-sors becomes more important as bio-logical analysis systems shrink. Thisproject integrates vertical cavity sur-face emitting lasers (VCSELs), PIN pho-todetectors, and optical emission filtersto be used as a f luorescence sen-sor. Integrating these components willdrastically reduce the size and cost offluorescence detection systems, andparallel sensing architectures of morethan 100 channels will be possible.(Work performed by SNF researchersEvan Thrush, Ofer Levi, James S. Harris Jr.,and Stephen J. Smith.)

• Microfluidic Channels With Integrat-ed Ultrasonic Transducers — Recentdevelopments in the field of ultrasonicMEMS devices are being used to inte-grate ultrasonic sensors and actuatorsin biofluidic channels. The integrationof ultrasonic transducers in small chan-nels enables applications that previous-ly were in the domain of larger-scale

sensors and actuators. Silicon microma-chined ultrasonic capacitor transducers(CMUTs) and zinc oxide-based piezo-electric transducers are being studiedfor use in flow measurement, fluidpump, pressure, density, viscosity,and other mechanical properties.(Work performed by SNF researchersGoksen G. Yaralioglu and HemanthJagannathan, with B.T. Pierre Khuri-Yakub of Stanford’s Dept. of ElectricalEngineering.)

• Piezoresistive Pressure Sensors UsingCarbon Nanotubes — Traditional sili-con piezoresistive pressure sensors arehighly temperature-dependent. Onealternative material that has beenshown to exhibit the piezoresistiveeffect is the single-walled carbon nan-otube (SWNT), a single graphene sheetrolled into a cylinder. SWNTs were grownon suspended polysilicon membranes,and air pressure was applied uniformlyto press down on the membranes, caus-ing the tightly attached SWNTs todeform.The current passing through theSWNTs was measured with respect tocontinuous time. The team’s designs canbe used in further investigation on thepotential of SWNTs as piezoresistivepressure sensors. (Work performed by Dr.

SNF is housed in the Paul Allen Center for Integrated Systems (CIS) building on the Stanford campus.


Nanotech Briefs 29 O c t o b e r 2 0 0 3Nanotech Briefs 29 O c t o b e r 2 0 0 3Nanotech Briefs 29 O c t o b e r 2 0 0 3

INSIDE

Hongjie Dai and Randy Grow of Stanford,and researcher John Liu of the Universityof California Irvine.)

• Micromachined Sensors for Biologi-cal Measurements — A collaborationbetween SNF and members of the Uni-versity of California at Berkeley is seek-ing to create a micromachined multi-axis force sensor to study biomechani-cal forces produced by insects such ascockroaches. The device enables three-axis measurement of ground reactionfoot forces produced by runninginsects. The sensors, while originallydesigned to study insect biomechanics,also enabled the first detailed measure-ments ever made of biomechanicalforces produced by ants as small as 4mg. (Work performed by SNF researcherMichael S. Bartsch, with Thomas W.Kenny of Stanford’s Dept. of MechanicalEngineering.)

• Silicon Micropumps for IC ThermalManagement — New approaches tothermal management are necessary dueto increases in high-end chip perform-ance. An SNF team is developing thermalmanagement systems based on microflu-idic networks. Electro-osmotic pumpingis a key enabling technology for suchsystems. These pumps operate well atthe micro scale, require little power, andsince they have no moving structuralelements, they are inherently reliable.The electro-osmotic pumps leverageelectrochemical interactions at a liquid-solid interface to induce flow through

the application of an electric field. (Workperformed by SNF researcher Daniel J.Laser, with Kenneth E. Goodson, Juan G.Santiago, and Thomas W. Kenny of Stan-ford’s Dept. of Mechanical Engineering.)

• Probe System for ElectrochemicalAnalysis in Nanometer Dimension —A pencil-shaped electrochemical trans-ducer system for analysis or surfacemodification in the nanometer dimen-sion has been developed. High-aspect-ratio tip structures are shaped by com-bining isotropic and anisotropic deepreactive etch processes to form thebody of the transducer. Due to the highaspect ratio topography, the probe iswell suited for Scanning Electrochemi-cal Microscope (SEM) methodologies.The technology also shows production

possibility for both probe-arrays andprobes on cantilevers. (Work performedby SNF researchers R. Fasching, Y. Tao, andK. Hammerick, with F. Prinz of Stanford’sDepts. of Mechanical Engineering andMaterials Science.)

Working With SNFLab membership at SNF is open to any-

one from any academic, government, pri-vate, or industrial organization. SNF wasdesigned to serve as a sophisticated “sand-box” where lab members can work hands-on with a broad range of state-of-the-arttools generally unavailable to researchersin academia or in small companies.

For information on SNF’s facilities,including becoming a user, visit http://snf.stanford.edu .

A micromachined force sensor measures foot forces produced by running insects such as this 1gcockroach.

A Unique Network

SNF is one of five founding members of the National

Nanofabrication Users’ Network (NNUN), which was estab-

lished in 1993 by the National Science Foundation to expand

access to nanofabrication resources across the country. The

combined staffs of the NNUN — which includes, in addition to

SNF, the Cornell NanoScale Facility, the Penn State Nanofabri-

cation Facility, the Materials Science Research Center at

Howard University, and the Nanofabrication Facility at the

University of California Santa Barbara — have experience in

all phases of nanofabrication and its use in fields from

nanophysics to biology to electronics.

Recognizing the need to foster growth in many integrated

fields, the NNUN has chosen to focus on the interface

between biology and engineering. Clinical diagnostics and

high-throughput screening of genes and drug candidates are

prime areas of rapid growth in this field. NNUN Biology

Domain Experts serve as technical liaisons between the bio-

logical and engineering research communities, coordinating

resources and maintaining information on biotechnology

research.

For more information on the NNUN, and how to become a

user, visit www.nnun.org .


http://snf.stanford.edu

www.nnun.org

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