September 2012 Vol. 37 No. 9 www.mrs.org/bulletin Inside: Energy Quarterly Semiconductor nanowire building blocks ZnO: Nanogenerators to piezotronics Fighting cancer with nanoparticle medicines Smart materials for cell-biomaterial interactions Self-folding thin-film materials Extremes of heat conduction IN THIS ISSUE
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September 2012 Vol. 37 No. 9
www.mrs.org/bulletin
Inside: Energy Quarterly
Semiconductor nanowire building blocks
ZnO: Nanogenerators to piezotronics
Fighting cancer with nanoparticle medicines
Smart materials for cell-biomaterial interactions
Self-folding thin-film materials
Extremes of heat conduction
IN THIS ISSUE
High Voltage Engineering
Beam energies from 10 keV up to several 10s of MeV
Beam currents from 100 micro-amps up to several milliamps
Ion species, including H, He, B, P, As and others
Single wafer or batch processing of wafers up to and including 8”
In-air or in-vacuum cassette-to-cassette wafer handling
Alta Devices moves out of the lab and into the valley
Jessica M. Smith
865 Books
Composite reinforcements for optimum performance
Philippe Boisse
Reviewed by Erik Thostenson
871 Posterminaries
Good reads for the materials researcher
Steve Moss
866 CAREER CENTRAL
864 SOCIETY NEWSYMRS seeks award nominations for 2013
VOLUME ORGANIZERS
2013 Mark T. Lusk, Colorado School of Mines,f USA Eva Olsson, Chalmers University of Technology,f Sweden Birgit Schwenzer, Pacificfi Northwest National Laboratory, USA James W. Stasiak, Hewlett–Packard Co., USA
2012 Lei Jiang, Chinese Academy of Sciences,f ChinaSergei V. Kalinin, Oak Ridge National Laboratory, USAStéphanie P. Lacour, EPFL, SwitzerlandSteven C. Moss, Aerospace Corporation, USA
2011 Kyoung-Shin Choi, Purdue University, USAReuben T. Collins, Colorado School of Mines,f USASean E. Shaheen, University of Denver,f USA
MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin788
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2012 MRS BOARD OF DIRECTORS
President Bruce M. Clemens, Stanford University, USAImmediate Past President James J. De Yoreo, Lawrence Berkeley Nationaly
Laboratory, USAVice President and President-Elect Orlando Auciello, Argonne National
Laboratory, USASecretary Sean J. Hearne, Sandia National Laboratories, USATreasurer Michael R. Fitzsimmons, Los Alamos National Laboratory, USAExecutive Director Todd M. Osman, Materials Research Society, USA
Wade Adams, Rice University, USAAna Claudia Arias, University of California–Berkeley,f USAShenda Baker, Synedgen, Inc./Harvey Mudd College, USATia Bensona Tolle, U.S. Air Force Research Laboratory, USADuane B. Dimos, Sandia National Laboratories, USAChang-Beom Eom, University of Wisconsin-Madison,f USAEric Garfunkel, Rutgers University, USAJ. Murray Gibson, Argonne National Laboratory, USAOliver Kraft,r Karlsruhe Institute of Technology,f GermanyHideki Matsumura, Japan Advanced Institute ofe Sciencef ande Technology, JapanStephen K. Streiffer, Argonne National Laboratory, USAJames C. Sturm, Princeton University, USASusan E. Trolier-McKinstry, The Pennsylvania State University, USAPierre Wiltzius, University of California–Santaf Barbara, USA
MRS OPERATING COMMITTEE CHAIRS
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About the Materials Research Society
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The Materials Research Society (MRS), a not-for-profitscientificfi association founded ind 1973, promotes interdiscipli-nary goal-oriented basicd research on materials of technologi-fcal importance. Membership in the Society includes almost16,000 scientists, engineers, and research managers fromindustrial, government, and universityd researchy laboratoriesh in thenUnited Statesd and overd 80r countries.
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MRS publishes The MRS Online Proceedings Library, MRSBulletin, Journal ofl Materialsff Research, MRS CommunicationsS ,and otherd publicationsr related tod current researcht activities.
Special ConsultantsMridula Dixit Bharadwaj
Energy Quarterly Steve M. Yalisove (Chair),V.S. Arunachalam, Anshu Bharadwaj,David Cahen, Russell R. Chianelli,George Crabtree, Abdelilah Slaoui,Guillermo Solórzano,and M. Stanley Whittingham
789MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
NEWS & ANALYSIS RESEARCH/RESEARCHERS
Lifetime variation in giant nonblinking QDs due to switching between neutral and negatively charged states
Nano Focus
Quantum dots (QDs) are attractiveas nanoscale light sources,t but thet
fluctuationsfl in emission intensity fromindividual dots, which is known as“blinking,” can limit their application.rIt has recently been shown that CdS/CdSe core–shell nanoparticles with thickhshells do not exhibitt blinking.t However,as reported byd ay Losa Alamos team, Chris-tophe Galland (nowd at thet University ofDelaware), Yagnaseni Ghosh, AndreaSteinbrück, Jennifer A.r Hollingsworth,Han Htoon, and Victord I.r Klimov in the
June 19 issue of Nature Communica-tions (DOI: 10.1038/ncomms1916), gi-ant nonblinkingt QDs (g-QDs) exhibit atpronounced variationd in their emissionrlifetimes due to a switching betweennegatively charged andd neutrald states.
In theirn study,r the researchers investi-gated thed optical behavior ofr individualfCdSe/CdS g-QDs with a 15 monolayerthick shell.k Individual g-QDs producedstable photoluminescence intensitieswith variations fitting a single-peakPoisson distribution.n Such behavior sug-rgests emission occurred from a singlestate. However, lifetime measurementsrevealed the presence of twof equallyweighted lifetimes (19 ns and 39 ns),thereby demonstrating that twot distinctstates contribute to the emission.
This behavior wasr linked tod the pro-cess of nonradiativef Auger recombina-rtion and itsd different effectt ont negativelycharged excitonsd (negative trions) versuspositively charged excitons (positivetrions). Neutral QDs correspond tod thebright optical state. In thin-shell QDs,charged excitons are essentially non-emissive because Auger decay is fast.However, in g-QDs,n Auger processesr arelargely suppressed for negative trions.By adding a single electron to the QD,the number ofr radiativef recombinationpathways is doubled, as is the radiativedecay rate. Charging is thus accompa-nied by a decrease in the photolumi-nescence lifetime without affectingt theintensity (“lifetime blinking”).
The investigators confirmedfi thisd sce-nario by studyingy the effect oft controlledfelectrochemical charge injection on theQD photoluminescence and relaxationrates. At 0t V, the equal distribution be-tween the two lifetimes was again ob-served. When either 0.5 V orV 0.8 Vwas applied, electron injectionn wasn morefavorable, and thed shorter lifetimer (19 ns)predominated without any change inphotoluminescence intensity. The re-search team concluded that observedlifetime fluctuationsfl are connected torandom charging of thef g-QDs withexcess electrons. Moreover, they foundthat chargingt occurs by Auger ionizationrthrough ejection of af hole. This Augerdecay pathway is favored ind g-QDs be-cause of af greatera degreer of conf fi nementfifor holesr than forn electrons.r These resultsshow that nonblinking behavior is notincompatible with random charge fl uc-fltuations in the QD.
Anthony S. Stender
In thin-shell QDs (a) charging is one of thef mechanisms causing luminescence intensityfl uctuationsfl known as blinking. This is because light emission from the negativelycharged exciton (X–X )– is quenched by very fast Auger decayr (negative trion pathway,curved arrows). In contrast, in g-QDs (b), nonblinking emission intensity is observedbecause Auger recombination of thef negative trion is suppressed. The only signatureof chargingf is a doubling of thef radiative decay rate compared to the neutral exciton((( r 2 r; double orange arrow). This is indicated by the plot of time-resolvedfphoton-counting data on the lifetime-intensity distribution map (lower right). Chargefl uctuationsfl are caused by Auger ionization of thef g-QD, that is, by the decay of afbiexciton through the fast positive trion pathway with ejection of thef hole. This pathwayis favored in g-QDs because of af pronounced asymmetry in spatial distributions ofelectron and hole wave functions in these nanostructures.
Wireless PV retinal prosthesis shows promise for restoration of sight
Bio Focus
Retinal degenerative diseases lead todblindnessRR due to the loss of photo-f
receptors even though the inner retinalrneurons remain largely intact. Visualpercepts, also called “phosphenes,”d can
be produced byd electrical activation ofthe inner retinalr neurons. This alternateroute to visual information has the po-tential for restoring sight to the blind.Current retinalt prosthesis designs, withelectrode arrays implanted ind the retinafacing either the ganglion cells or theinner nuclearr layer,r rely on serial telem-etry to deliver stimulationr signals to theelectrodes, requiring bulky receivingy and
processing electronics and ad trans-scleralacable. Surgery isy complex and thed designis diffiff cultfi to scale up to attain highervisual acuity. In addition,n patients cannotuse natural eye movements to scan thevisual scene because retinal stimulationpatterns are transmitted fromd an externalncamera to the retinal implant, indepen-dent oft eyef orientation. These limitationscan be overcome by devices that use
Subretinal photodiode array with triple-diode pixels arranged in a hexagonal pattern.Pixels of 70f μm and 140 μm in size were made. Left inset: Central electrodes are sur-rounded by three diodes connected in series, and by the common return electrode.Right inset: The subretinal implant.
photosensitive pixels but they dependon an external power source.r Recently,however, researchers from the Palankergroup at thet Hansen Experimental Phys-ics Laboratory and the Department ofOphthalmology at Stanford Universitydesigned ad photovoltaic retinal prosthe-sis where video goggles were used tod de-liver bothr power andr visuald informationthrough pulsed NIR illumination,R pre-serving the natural link betweenk imageperception and eye movement withoutcomplex electronics and wiring.d
In an article published ind the June is-sue of Nature Photonics (DOI: 10.1038/nphoton.2012.104; p. 391), Keith Ma-thieson, James Loudin, and co-research-d
ers from Stanford University and theUniversity of California–Santaf Cruz,describe their prosthesisr design in whichnvideo images captured byd ay head-mount-aed camerad are processed byd a portablecomputer. The video goggles use a liq-auid-crystal display (LCD)y illuminated bydpulsed near-infraredd lightd (880–915t nm)to project thet images onto a subretinalphotodiode array (consisting of 70f mpixels, each with ~20 m stimulatingelectrodes), which converts the light totlocal currents that stimulatet the nearbyneurons in the inner nuclear layer ofthe retina.
The researchers fabricated silicond pho-ntodiode arrays consisting of pixelsf with
Optical confi nement modifi es graphene transistor characteristics
Nano Focus
The interaction between light andmatter can be greatly enhanced
within an optical cavity in which thespacing of twof mirrors definesfi a stand-ing electromagnetic wave. Placing asheet oft graphenef in such a cavity cantherefore have profound effects on itsoptoelectronic properties, as shown by
M. Engel of thef Karlsruhe Institute ofTechnology, M. Steiner ofr thef IBM T.J.Watson Research Center inr New York,A. Lombardo of thef University of Cam-fbridge, and theird colleagues.r Their articlerin the June 19 issue of Nature Commu-nications (DOI: 10.1038/ncomms1911)describes how such optical confinementfiof af graphenea transistor allowsr spectrallyselective generation of photocurrentf andteven alters the electrical transport prop-terties of thef material.
The team embedded ad sheet oft gra-f
phene between two optically transpar-ent dielectrict materials, Si3N4 and Ald 2O3,which are in turn enclosed byd silver mir-rrors with a spacing equal to one-half offthe resonant wavelength of thef cavity.At the center ofr thisf optical cavity theanti-node in the optical fi eldfi enhancesthe absorption orn emissionr ofn photonsf bythe graphene at thet resonant wavelength,tand inhibitsd it att othert wavelengths.r Ap-plying a voltagea across the graphene andilluminating the device with a laser gen-rerated 20d times more photocurrent att thet
single diodes as well as those consistingof pixelsf with three diodes connectedin series. These triple-diode pixels canproduce 1.5 V, which triplesh the chargeinjection onn then sputtered iridiumd oxidemfilmfi electrodesm (from 0.5m mC cm 2 for arsingle-diode pixel to 1.5 mC cm 2). Thetriple-diode pixels require light intensitiestthree times higher thanr single-dioden pix-els because the photosensitive pixel areais divided intod three subunits. However,the researchers found thatd theirt single-rand triple-dioded devices had veryd similarythresholds for elicitingr retinal responses.
The researchers tested their designconcept byt stimulating healthy and de-dgenerate rat retinas in vitro with NIRlight intensities at least two orders ofmagnitude below the ocular safetyr limit.They showed thatd thet elicited retinald re-sponses can be modulated byd both lightintensity and pulsed width, although theircurrent optical design allows only forintensity modulation within each videoframe. However, if thef retinal responseis modulated byd varying the pulse width,the researchers said thatd digitalt light pro-tcessing technology can also be used,adding, “Such ah devicea would allowd bothwthe duration and timingd of exposuref tobe precisely controlled on the scale ofindividual pixels. In addition to higherthroughput compared to an LCD, thishigh-speed controld would allowd the se-quential activation of nearbyf pixels tofurther reducer pixel crosstalk—interfer-ence of currentsf from nearby pixels.”
Steven Trohalaki
791MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
NEWS & ANALYSIS RESEARCH/RESEARCHERS
resonant wavelength,t providing a spec-tral selectivity not observed in uncon-finedfi graphene. Similarly, when a cur-rent ist applied tod unconfi nedfi graphene,d it
heats up and emitsd a featureless thermalspectrum, whereas the graphene in theoptical cavity displays a stronga emissionpeak atk thet resonant wavelength.t
The researchers also found thatd con-tfi nedfi graphened exhibited unusuald electri-cal behavior. At lowt voltages the cavityinhibits the emission of thef low energythermal radiation with wavelengthslonger thanr resonance, and the currenttherefore saturates. As the voltage isincreased, this threshold ford lightr emis-tsion is passed andd thed device resistancedrops accordingly.
Graphene is an ideal material forthis type of devicef because of itsf two-dimensional nature, which allows it toextend ford micrometersr across the centerof thef cavity, and easilyd tunable electri-cal properties. The degree of spectralfselectivity provided byd the optical con-fi nementfi suggests a useful applicationin photodetection, while its influencefl onelectrical transport couldt bed exploited indnanoelectronic devices.
Tobias Lockwood
Weakly charged cationic nanoparticles unzip DNA
Bio Focus
Understanding the interaction be-tween charged nanoparticles and
double-stranded DNA hasA importantimplications for drugr delivery schemesand DNA-templated metallization,in addition to other possible applica-tions. While attempting to packageDNA ontoA nanoparticles as a meansof genef delivery into cells, Anatoli V.Melechko of Northf Carolina State Uni-versity (NCSU), Timothy E. McKnightof Oakf Ridgek National Laboratory, andtheir colleagues discovered somethingcompletely unexpected. Some of thefnanoparticles clumped together,d and indthe process pulled thed double-strandedDNA apart,A at leastt partially.t
“This could bed a newa type of machin-fery that cant be used ford separatingr DNAinto single strands,” Melechko said, ad-mitting that at lot moret work willk needto be done to understand and controlthe phenomenon.
In nature, negatively charged DNAwraps around protein cylinders with apositive charge of +220f to form a com-
plex known as chromatin. A highA posi-tive charge on a protein or a nanopar-ticle causes DNA toA bend andd undergodcompaction. Much work hask been donewith functionalized nanoparticlesd in thisregime. Some research has been donewith weakly positive charged nanopar-dticles, which typically have no effect ontthe conformation of DNA.f In choosinggold nanoparticles (AuNPs) function-alized with thiolated alkane ligandsbearing primary amines with a chargeof +6,f Melechko and his colleaguesexplored the lesser-known transitioncharge region between the weak andk thedstrong regimes.
As reported in the August 16 issueof Advanced Materialsd (DOI: 10.1002/adma.201104891; p. 4261), gel electro-phoresis experiments with the AuNP-DNA showedA ad “mysterya bandy ind an gel—aan extra line [close to the 1000 base pairmarker] that createdt thed main puzzle forus,” Melechko said. Though prior workrby others might signifyt that thist mysteryline was the result oft DNAf compactionAaffecting gel mobility, Melechko and co-dworkers hypothesized thatd somet denatur-ing—or unzipping—ofr thef two-strandedDNA wasA occurring. UV spectroscopyV
showed that at least partial denaturingwas occurring.
To better understand the phenom-enon, co-researcher Yaroslavar Yinglingof NCSUf ran molecular dynamicsr simu-lations involving single AuNPs with sixcharged ligands (AuNP 6NH3
+), andcompared them with other moleculardynamics simulations involving threeof thef AuNP 6NH3
+ units. The single-particle simulations showed bindingd ofthe ligands to both the minor andr majordgrooves of DNA,f but littlet structural al-teration inn then double helix. Basically, theDNA justA stickst to a single nanoparticle.But int the three-particle simulations, thenanoparticles bunch together. “You haveuhydrophobic groups that want to hidebetween themselves, and polar groupsthat grabt on to DNA,” Melechko said.“When they do this clumping and stilldhold ond to DNA, they can rip it apart.”t
The researchers said that “particlesacting in concert cant produce effects notpossible with single particles.” A videoAof thef molecular dynamics simulationcan be viewed at http://youtu.be/9M-58niEOpU.
The battle over rarer earths seems tohave become the most bittert inter-r
national trade dispute this decade. Coun-tries have become increasingly con-cerned thatd Chinat isa gaining a monopolyaover ther production of thesef elements,which are critical to green energy andhigh-tech industries. The United States,dfor example,r once produced alld its rare-earth elements domestically, but hast be-come wholly reliant ont Chinese importsover ther last 15t years. During disputesthrough the World Traded Organization,China said thatd its policies in questionare aimed atd protectingt natural resourcesand achievingd sustainable economic de-velopment. Meanwhile, one of thef fewsolutions for countriesr suffering a supplyashortage is to launch their ownr miningefforts. And thatd ist exactly what China’stneighbor, India, is now planning to do.
India’s Ministry of Minesf has formeda steering committee to investigate re-starting exploration of raref earths, with aparticular eyer on India’sn growing renew-able energy sector. Modern electronictechnologies depend ond rare earths, andwith government targetst for ar total ca-
pacity of 20f GW ofW on-gridf solard powerrby 2022, and 40d GW ofW windf power,d theGeological Survey ofy Indiaf hasa made ex-ploration ofn raref earths a higha priorityh foryits next five-yearfi plan.r
“With limited availability of rarefearths, and thed projected growthd in de-mand, supply chainy vulnerabilityn mayy setyin,” said Rangacharid Krishnan, chief ad-fvisor tor the Center forr Studyr of Science,fTechnology andy Policyd iny Bangalore,n andformer headr ofd thef Metallurgy Divisionat thet Bhabha Atomic Research Centre.
The elements particularly in demandinclude neodymium, which ish used ind thenpermanent magnetst inside the compactmotors of windf turbines, and dyspro-sium, which is used to raise the Curietemperature of thef magnets of electricfvehicles. “The typical weight oft af 1-MWawind generatord isr around 600d kilograms,out oft whichf neodymium is around 25%dand dysprosium is about two to threepercent,” said Krishnan.d Cerium oxideis used ford UVr absorptionV inn solarn panels,rand lanthanumd is required ford catalyticrcracking in then petroleum industry. Indiaalso has a large and increasingd demand
If Indiaf doesbegin mining rareearths, it will notbe for ther firstfi time.“India was a leadingproducer and sup-plier of raref earths50 years ago,” saidKrishnan, particu-larly of yttrium.fAbout five yearsago, however, thecountry froze min-ing and developmentd
of rare-earthf elements because of af lackof competitionf in the domestic market,which made Chinese imports cheaper.
Now, as before, the Atomic Miner-als Directorate, a unit oft India’sf Depart-ment oft Atomicf Energy, is at thet heartof explorationf since a major sourceof raref earths is monazite sands, fromwhich radioactive thorium and uraniumdare also extracted. “India possesses thelargest depositst of monazitef in then world,mostly in the coastal tracts of Orissaf onthe east coastt andt ind Kerala on the westcoast. Besides the beach sands, mona-zite has been reported ind carbonatites inMeghalaya, Tamil Nadu, and Assam,”said Krishnan.d
According to the Prime Minister’s of-fice,fi these reserves stand atd aboutt 10.7tmillion tons, translating to roughly 5million tons of rare-earthf oxide.
Indian Rare Earths Ltd. (IREL), thecountry’s only rare-earths producer, issetting up a processing plant int the east-ern staten of Orissaf toa produce 11,000 tonsof rare-earthsf chloride, which inh turnn cannbe converted tod rare-earth oxides. Alongwith a smaller plantr alreadyt in operationin Kerala, they are expected tod producearound 2250d tons of rare-earthf oxides inthe last quartert ofr 2012.f
The Japanese firmfi Toyota Tsushoa hasentered intod an agreement witht IREL toLset upt a plant att Visakhapatnamt in East-ern India to produce rare-earth oxides,and the company expects an export ofabout 4000t tons of thef material from this
India to reopen miningfor rare-earth elements
Mineral-rich “black sands” in Kollam, a coastal district in the Indianstate of Kerala.f These sands are a valuable source of monazite.f
Yvo
nM
auric
e
BastnäsiteExtract: Cerium
MonaziteExtract: Thorium and uranium
XenotimeExtract: Dysprosium
Kerala
Tamil Nadu
Orissa
Chhattisgarh
Jharkhand
MeghalayaAssam
gggggg
West Bengal
793MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
NEWS & ANALYSIS SCIENCE POLICY
plant. In July 2011, it began construc-tion of a plant that “makes use of thispreviously unexploited mixture as a raw material to produce such rare earths as neodymium, lanthanum, and cerium,”according to the company’s website.
Sizable deposits of xenotime, a phos-phate mineral that contains the heavier rare earth dysprosium, have also beenfound in the states of Chhattisgarh and Jharkhand. Meanwhile, bastnäsite—a source of cerium—has been found in the state of West Bengal. As yet, though, the extent of India’s reserves is not fullyknown. Of the 6500 kilometers of In-dian coastline, the Geological Survey of India has only explored 2200 kilometers,according to Krishnan. He also warns
that the process of starting such miningoperations is likely to be slow: “Fromexploration until setting up an extractionplant may take more than 10 years.”
Despite its latest efforts, however,India is unlikely to challenge China in its dominance over the global supply of rareearths, according to Naresh Pant, associ-ate geology professor at the University of Delhi. “That would require at least anorder of magnitude increase in produc-tion,” he said. India’s rare-earth reserves stand at just more than three milliontons, he said, while China has more than 36 million.
At the moment, the lack of rare-earthdeposits in the European Union means that it imports USD$458 million of rare
earths annually from China. Accordingto the US Department of the Interior,the United States has around 13% of global reserves of rare earths, Russiahas 17%, and Australia has 1.5%, yet all these nations depend on imports, too. Complaints to the World TradeOrganization have focused on the fact that China—which has around 37% of reserves and supplies around 97% of theworld’s rare-earth elements—is threaten-ing businesses by restricting exports. For India, which also relies on Chi-nese rare earths, restarting rare-earths processing, mining, and exploration may at least offer a ray of hope as sup-ply shortages begin to bite.
Angela Saini
NSF and EC establish collaboration opportunities for early career scientists
The US National Science Foundation (NSF) and the European Commis-
sion (EC) signed an Implementing Ar-rangement to provide opportunities for NSF-funded early career scientists and engineers to pursue research collabo-
rations with European colleagues sup-ported through the European Research Council (ERC) awards. The agreement supports collaborations on specifi c proj-fiects while leveraging research fundingand fostering lasting collaborations be-
tween European and US researchers. European Commissioner for Re-search, Innovation and Science Máire Geoghegan-Quinn and NSF Director Subra Suresh signed the arrangement onJuly 13 at the European Science OpenForum in Dublin.
Monash University, with the support of the Australian government’s
investment of AUD$30 million under Prime Minister Julia Gillard, will man-age the Australian Synchrotron program. Australian universities will also investaround AUD$25 million. Announcingthe funding, Science and Research Min-
ister Senator Chris Evans said with the strong need to undertake research and development to transform industriesand see them through challenges such as climate change, economic change, and skills shortages, there has never been a more vital time to invest in the facility. “As the Australian Synchrotron can
be used to study the most precise natureof any biological and industrial material,it can be used by almost any industry across a wide range of research fields,” fisaid Evans.
The AUD$30 million government in-vestment is being provided by the Aus-tralian Research Council (AUD$25 mil-lion) and National Health and Medical Research Council (AUD$5 million).
Brazil and China discuss 10-year cooperation plan
During the Rio+20 Summit held inJune, Brazil and China signed the
Ten-Year Cooperation Plan 2012–2021. In July, Brazil’s Minister of Science, Technology and Innovation (MCTI),
Marco Antonio Raupp, traveled to China to meet with the Chinese Ministers of Science and Technology, Wan Gang, and Industry and Information Technology, Miao Wei, and the head of the Chinese
National Space Administration (CNSA), Chen Qiufa, to discuss numerous top-ics, including the Bi-National Center for Nanotechnology and memorandums of understanding for biotechnology and meteorology centers.
MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
BEYOND THE LAB
794
FEATURESFEATURES
Jessica M. Smith
Alta Devices movesout of the lab andinto the valley
In the world ofd technologyf start-ups,especially clean energy, “the val-
ley”—also known as “the valley ofdeath”—refers to the gap in capital be-tween then funding of invention—throughfgovernment grantst and ventured capital—and massd production. Recently, the thin-filmfi solar-cell manufacturer Solyndrafamously failed tod cross this valley, de-claring bankruptcy after acceptingr mil-lions of dollarsf in US government gaptfunding. The controversy around thisparticular case,r and around the fate ofmany solar start-ups generally, meansthat allt eyes are on Alta Devices. As thestart-up begins production on its pilotline, the clean energy community willwatch as Alta Devices attempts to takeits technology out of thef lab and intothe valley.
Alta Devices was founded byd HarryAtwater of thef California Institute ofTechnology and Eli Yablonovic of thefUniversity of California–Berkeleyf incollaboration with venture capitalistAndy Rappaport. The company relieson Yablonovic’s research in the 1980son a technique called epitaxial liftoff.The active layer Altar Devicesa uses in so-lar cells,r gallium arsenide (GaAs), canbe produced inexpensively using thistechnique without degradingt the perfor-mance of thef cell. The team began thecompany in 2007, and hasd subsequentlyworked towardd perfectingd epitaxial lift-off off GaAsf at at laboratory scale. Whenthe pilot productiont line opens later thisryear, this invention will be produced fordthe firstfi timet on large scale.
Epitaxial liftoff isf an effiff cientfi wayto create thin wafers of GaAs.f On topof af high-purity GaAs surface, layers ofGaAs are deposited withd alternating lay-ers of aluminumf arsenide (AlAs). “Wetake advantage of thef serendipitous fact
that the etch selectivity between AlAsand GaAsd is more than 100 million, sothat it’st possible to immerse the structurein an etching solution and remove theAlAs layer completelyr without etchingtthe GaAs layer,” said Atwater.d The freeGaAs wafers are of veryf high purity, andthe original GaAs surface can be usedagain to create more wafers.
Solar cells made from these GaAswafers compare favorably to conven-tional silicon photovoltaic (PV) cells.The highest performing silicon PVcells are made out of high-purityf sili-con, similar tor that found in computerchips, which allows them to reach solarconversion effiff cienciesfi near 30%.r Thesilicon used ind these cells, however, iscostly to produce, and thed cells requirea thick layer in order to reach max-imum effiff ciency.fi
Gallium arsenide PV cells madethrough epitaxial liftoff canf also reachhigh effiff ciency—currentlyfi 23.4% andclimbing. Because of thef properties ofGaAs, effiff cientfi solart cellsr can be madewith a much thinner layerr ofr material.fCombined withd the less expensive pro-cessing method, Alta Devices'a solar cellsrcan be made for ar fraction of thef cost oftsilicon PV cells.V
The conventional wisdom ofm thef pho-tovoltaics community is that any solarcell that ist inexpensive to produce mustalso have a low effiff ciency.fi For instance,rpolymer PV cells, or those made withamorphous cadmium telluride, have ef-ficienciesfi below 10%. As a result, anycost eft fiff ciencyfi is mitigated byd the smallamount of electricityf that will comeout oft onef of thesef solar cells.r Throughepitaxial liftoff, Alta Devices’ galliumarsenide solar cellsr can be both highlyeffiff cientfi andt inexpensive.d
Alta Devices is working toward fur-dther increasing the effiff ciencyfi of theirfsolar cells.r Atwater said,r “We see 30%[effiff ciency]fi as an achievable limit. Thatwas seen as a lunatic idea when we be-gan the company.”
Rappaport agreed, adding, “Fortu-nately, you found ad lunatic.” Rappaport
Alta Devices founder Harry Atwater (right) of thef California Institute of Technologyfwith venture capitalist Andy Rappaport of Augustf Capital describe the early develop-ment of thef company at the Technology Innovation Forum held at the 2012 MaterialsResearch Society Spring Meeting in San Francisco.
795MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
FEATURES BEYOND THE LAB
had never invested in a clean energycompany before and saidd hed is unlikelyto invest int one again. “A problemA withsolar start-upsr is that mostt oft thef inno-vation is around productiond methods atscale. It’s expensive to get to scale!”he said. He liked Altad Devices becauseit was the fi rstfi solar company he hadseen that was fundamentally different.“The cost-effiff ciencyfi curve had gottento be conventional wisdom.” That AltatDevices had ad way to deviate from thecost-effiff ciencyfi curve convinced Rap-paport and became the foundation ofthe company.
Alta Devices' leaders believe thatthey can findfi a market for their solarcells soon after theyr optimize the pilotline. They said theird thin,r flexible,fl high-effiff ciencyfi panels will be ideal for aero-rspace and militaryd applications in whichthe right combination of propertiesf ismore important thant cost fort ar PV cell.VThese customers will give the companytime to decrease manufacturing costs,according to Rappaport. “When we arefar downr the learning curve, we shouldbe as cheap, or cheaper,r than anythingelse out there.t Eventually, we should bedthe best solution to utility scale solar,but wet don’t havet to immediately trans-port ourselvest to the end ofd thef learningcurve. We get tot gradually get there.”t
At thet same time, another earlyr ap-plication for ar fl exible,fl high-effiff ciencyfisolar cellr could bed implemented ind de-veloping countries. “Worldwide energy
production and consumption has beenhampered ind a verya general way becauseof thef high infrastructure cost oft distri-fbution. If you’ref able to generate powerlocally, you reduce the dependence onexpensive, diffiff cult-to-constructfi distri-bution systems. We’re building some-thing lightweight, portable, and cheap,dso we’re contributing to a notion of lo-fcal power generation.”r Rappaport saidthat the same properties that allow theAlta Devices’ solar cellsr to be useful tomilitary operations could alsod be usefulin places that lackt energyk infrastructure.
To be used inother countries, par-ticularly in Europe,the solar cells mayneed to be part of afrecycling schemebecause of thef coun-tries’ strict regula-tions with respect totoxic materials. Forinstance, the Restric-tion of HazardousfSubstances Directive,a policy of thef Euro-pean Union, banscadmium in all con-sumer products. Toreceive permission to
sell panels in the European Union, FirstSolar, which makes cadmium telluridesolar cells,r had tod agree to remit allt of thefpanels back tok their factoryr in Arizonaat thet end ofd life.f “People regarded thatdas being a significantfi liability,”t Atwatersaid, referring to the high insuranceh coststo First Solar.t “They’re profitablefi evendoing this recycling. They’re headingoff thef criticism that theyt will leave theworld withd an environmental obligationif theyf go bankrupt.”
In Alta Devices, the toxic element oftconcern is arsenide. Atwater saidr that,increasingly, solar companiesr do recyclepart oft theirf solarr cells.r He said, “I imag-ine Alta will follow suit ast a responsiblecorporate citizen.”
Given then challenges facing solarg start-rups, considering a recyclinga policy beforeylaunching a pilota linet may seemy optimis-mtic. Luckily, the founders of Altaf Devicesaseem tom overflrr owfl withw optimismh thatm theythave discerned thed right combinationt ofntechnology andy businessd strategy. Despitethese assets, to land ond then other sider of“the valley ofy death”f as a solara companyrthat manufacturest a newa materialw will bea signia ficantfi accomplishment.t
Alta Devices’ GaAs high-efficiency,fi ultrathin solar panel.
David Parrillo of Thef Dow Chemical Company (second from left) moderatedthe Technology Innovation Forum with panelists (from left to right) Rappaport;Atwater; Joseph Foster, Alta Devices Vice President of Businessf Development;and Fred Farina, Caltech’s Chief Innovationf Officerfi and Executive Director of thef Officefiof Technologyf Transfer.
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MRS BULLETIN VOLUME 37 SEPTEMBER 2012 www.mrs.org/bulletin Energy Quarterly
Energy QuarterlyNews and analysis on materials solutions to energy challenges
Inside:
EDITORIAL
Billboard science
ENERGY SECTOR ANALYSLL IS
High-temperature superconductors
change the game
INTERVIEW
From materials research
to climate change:
David Eaglesham assesses
the solar energy industry
Supplementary: Video selections
from Eaglesham interview online
REGIONAL INITIATIVE
Supercapacitors take charge in Germany
ENERGY FOCUS
ENERGY QUARTERLY ORGANIZERS
CHAIR Steve M. Yalisove,YY University of Michigan, USA
V.S. Arunachalam, Center for Study of Science,
Technology and Policy, India
Anshu Bharadwaj, Center for Study of Science,
Technology and Policy, India
David Cahen, Weizmann Institute, Israel
Russell R. Chianelli, University of Texas, El Paso, USA
George Crabtree, Argonne National Laboratory, USA
Abdelilah Slaoui, InESS, France
Guillermo Solórzano, PUC-Rio, Brazil
M. Stanley Whittingham, State University of New York
at Binghamton, USA
Images incorporated to create the energy puzzle
concept used under license from Shutterstock.com.
Energy Sector Analysis image of a variety of SuperPower 26 HTS
Billboard scienceWind Dies,d Sun Sets … You need reliable,d affordable, clean coal electricity.l This iswhat It recently read ond billboard afterd billboardr whiled driving through Pennsylvania.Coal may be cleaner thanr it was,t but itt stillt produces massive amounts of COf 2. WhileI was upset att thet message, I quickly began to admire the ability of thef coal industry
sears its message. This is no accident. Huge amounts of moneyf go into advertisingcampaigns. Claims are even made that solart panelsr emit radiation,t as found ond internetdiscussion forums such as Australia’s “Whirlpool” (http://forums.whirlpool.net.au)and governmentd policyt recommending people should remaind at leastt 4t meters awayto avoid exposured as reported byd the Israeli newspaper Haaretz. The materials com-
the resources to hire advertising agencies to do our workr fork us.r What wet can do is useour talentsr combined withd the internet tot get ourt messager out. While science museumexhibits and NOVAd showsA are great, a largea fraction of thef population never seesr them.Broadcast mediat (e.g., billboards, blogs, radio, and magazinesd like People) are themost commont source of informationf for ther general public. Luckily, these sources ofinformation are losing ground tod the internet. Hence, the materials community has agolden opportunity to reach the general public if wef are smart aboutt it.t Our communityrcan learn the skills of visualf communication. We can learn how to make science simple
major researchr university. The main purpose of thesef departments would bed to trainour scientistsr and engineersd in the elements of visualf communication and armd them
billboards on Pennsylvania highways.Steve Yalisove
MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin • Energy Quarterly
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Aquarter centuryr after ther Nobel-prize-winning discoveryin 1986 of thef firstfi “high-temperaturet superconductors”
(HTS), the once heady prospect of transformingf the electri-cal power industry with lossless superconductors operatingat liquidt nitrogend temperature is no longer ar dream. Years ofmaterials research and ad suite of highlyf successful demonstra-tion projects have put HTS not only on the doorstep of thefelectric power grid but of facilitatingf its entry into the 21stcentury, including the increasingly mandatory shift tot green,renewable energy.
The US National Academy of Engineeringf describes the vastnetworks of electrif fi cationfi known as the grid asd “the greatestengineering achievement oft thef 20th century.” But thet futuredemands better: a grid thatd ist not fragmentedt butd trulyt nationalin scope;n where large amounts of powerf canr ben transported overdvast distancest in a fl ashfl by underground cablesd from wherevergenerated tod wherever needed;r where networks are redundantto back up outages; where overloads, short-circuits, losses,and fl uctuationsfl can be instantly compensated; where fl eetsfl ofelectric cars can be plugged intod the grid tod recharge withoutoverloading it; and where the frequency and voltage of thefpower arer reliably maintained (increasinglyd essential for therdigital society).
Many think thek grid is not up to the demands of thef 21stcentury without at seriousa effort tot upgrade. A 2010A report titledt“Science for Energyr Technology” from the US Department oftEnergy’s (DOE’s) Offiff cefi of Basicf Energy Sciences offers anentrée for high-temperaturer superconductor powerr equipment,r[but] “to achieve competitive cost-performance, significantfi im-tprovements over existingr wire performance are still required.”Surveying current majort HTSr challenges, the DOE report says,t“chief amongf these [is] a majora increaser (at leastt at factora ofr two)fin high-temperature superconducting current-carrying capabil-ity under operatingr conditions.”
Superconductors are best knownt forn ther lossless transmissionof dcf electric currents when cooled belowd their transitionr tem-peratures. In service, however, superconductors contain arraysof nanosized,f quantized, “fluxfl tubes” or vorticesr of supercurrentfcirculating around non-superconductingd cores. Vortices are noproblem when pinned atd structuralt defects like dislocations or
impurities in the superconductor, but att at critical current, theybreak free,k dissipating energy asy they move,y thereby introducingya resistance.a In practice,n incorporating pinning defects designedto block vortexk motion raises the critical current tot levels thatare useful, but theret is much room for improvement.r
Determining the maximum critical current thatt couldt bed ob-tained byd introducing the “ideal” distribution of defectsf awaitsthe ability to understand thed behavior ofr largef arrays of vorticesfin a fieldfi ofd pinf sites. In large arrays, the best criticalt currentsare only ~20% of thef theoretical critical current, but whyt is notknown. “There’s some theory but stillt lots of empiricism,”f saidDrew Hazelton of SuperPower,f Inc., a major HTSr wire maker.
The availability ofy HTSf conductors will be an industryn game-ychanger saidr Steve Eckroad of thef Electric Power ResearchrInstitute (EPRI). Up until now, utilities have relied ond a high-voltage, low-current networkt basedk ond copper forr generators,rtransformers, and urband underground cablesd (rural overheadlines are usually aluminum). Superconductors with no dc andonly small ac losses plus high current densityt change the equa-tion to lower voltager and higherd current.r HTS cables have fi vefitimes the capacity in the same cross-sectional area as conven-tional copper cables.r
One way to exploit this capability is by combining HTSwith renewable energy sources for ar truly green grid ind whichremotely generated powerd fromr renewable sources could traveldto distant consumerst over whatr windt andd solard powerr advocatesrcall “green power superhighways.” However, long-distancetransmission is not yett at near-term prospect fort HTS,r owingto the huge capital investment costs and an unproven trackrecord ofd benef fits.fi
Here is where the ongoing materials research could payd off.Eckroad said,d “Our studiesr suggest thatt reducingt the presentcost oft thef superconductor byr a factor ofr twof would bringd thecost of 10-GW,f 1200-mile-long, superconducting cables towithin range of thatf oft conventionalf overhead lines.d Since un-derground dcd cables also offer substantialr environmental, siting,and aestheticd benefitsfi over conventionalr overhead transmissiondlines, they may become an attractive alternative option in somesituations.”
Whether cabler or somethingr else, every HTS power applica-r
High-temperature superconductors change the gameBy Arthur L. RobinsonFeature Editor James Misewich
Are high-temperature superconductors ready toy take on the grid?
James Misewich, Brookhaven National LaboratoryArthur L. Robinson, [email protected]
MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin • Energy Quarterly
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beginsn with compositeh “wires” in whichn theh superconductoris only one component. Doped bismuth-strontium-calcium-copper-oxygen (BSCCO) compounds emerged as the fi rst-figeneration (1G) HTS material for commercialr use. Kilometer-long wires of BSCCOf in a silver matrixr can now be routinelyproduced, but sincet the matrix is 60–70% of thef volume, thewire is inherently costly. Sumitomo Electric Industries remainsthe principal supplier ofr 1Gf wires.
“Around 1999,”d said SuperPower’sd Hazelton, “we looked atdthe cost projections,t and wed moved tod yttrium-barium-copper-oxygen [YBCO]-based second-generationd [2G] wires.” Othervirtues of 2Gf conductors include higher currentr andt betterd per-rformance in high magnetic fi eldsfi even though the transitiontemperature is somewhat lower. YBCO conductors take theform of af multilayer taper made from superconductor depositedronto a textured metallicd substrate. Two coated-conductor tech-rnologies have caught on,t one researched atd Oakt Ridgek NationalLaboratory and commercializedd byd American SuperconductorCorporation (AMSC) and thed other developedr atd Lost AlamosNational Laboratory and usedd byd SuperPower.
As the demonstration projects suggest, it ist largely govern-ment supportt thatt ist helping to grow an HTS industry aroundthe world. Alan Laudern ofr thef Coalition forn ther Commercial Ap-plication of Superconductorsf estimates that fromt 1993 through2011, DOE offiff cesfi alone have invested aroundd $600d million inthe United Statesd to develop HTS technology spanning materi-als research, wire (or conductor)r fabrication, systems assembly(cables, transformers, rotating machinery), and demonstrationdprojects involving utilities aimed atd establishingt the technicalreadiness of HTSf systems. “The DOE investment hast broughtHTS technology a long way,” says David Knolld of thef South-wire Company, an HTS cable manufacturer.
To take one example, serving congested urband environmentsas demand growsd inexorably is a utility priority. Beginning in
2003, the DOE’s Offiff cefi of Electricityf Delivery and EnergyReliability (DOE-OE) has sponsored demonstrationd projectsat utility substations with costs split roughly 50-50 betweenDOE-OE and industry.d Based ond ac HTS cables with typicallengths of af few hundred meters,d these projects demonstratedthe ability to add capacityd by simply replacing copper withr su-perconducting cables in existing utility conduits, thus avoidingthe expensive and dauntingd prospect oft diggingf up the streetsto install new ones. Though some feel it wast premature, DOE-OE deemed thesed so successful that itt ceasedt supportingd newefforts after 2009.r
Nonetheless, the importance of continuedf governmentd sup-tport at this stage of HTSf development is well illustrated inAsia. The Korean Electric Power Corporationr (KEPCO), 51%percent government-owned,t has a particularly ambitious planfor HTSr in itsn grid andd hasd recently installedy ad distributiona cablenat itst I’cheon substation. Construction of af power substationr inBaiyin, China’s Gansu province, is supported byd the ChineseAcademy of Sciencesf and thed State-owned Assetsd Supervisionand Administrationd Commission of Baiyinf City.
What cant motivate US utilities to take up where DOE leftoff? Unfortunately, said Josephd Minervini of thef MassachusettsInstitute of Technology,f “there are no killer appsr to do the job.”Syed Ahmedd ofd Southernf California Edison says that exploit-ting the benefitsfi of HTSf over ther next decadet is most likelyt tostart witht niche projects to build ad technologya foundation whilegradually expanding markets and growingd the manufacturingcapacity to supply them. Minervini added that “microgrids”for isolatedr militaryd bases and larged urban data centers mayprovide another entréer by avoiding the need ford investmentr bytrisk-averse utilities.
HTS fault-current limiterst (FCLs) fi tfi Ahmed’st scenario nice-ly, as demonstrated ind Europe. The Swedish utility Vattenfallhas installed ind Boxberg,n Germany, an FCLn madeL by the Frenchcompany Nexans. These devices prevent hight currents (faultcurrents) generated byd disturbances in the grid fromd causingoutages, but int the 21st century,t they must bet faster actingr andhigher capacityr to maintain the reliability and securityd of thefnetwork. In essence, HTS do this by rapidly transitioning to thenormal, non-superconducting state when the current exceedstthe material’s critical current.
Off-shore wind energyd may emerge as a renewable-energyapplication for HTS.r Superconducting generators can be morepowerful and much smaller than conventional devices, saidAlex Malozemoff off AMSC,f who foresees that HTSt will per-mit thet relatively compact, high-power windr turbinesd that cantmake off-shore energy affordable. Though HTS-based super-dconducting magnetic energy storage (SMES) is farther fromrcommercial deployment, Qiang Li of Brookhavenf NationalLaboratory said thatd thet fast responset and highd effiff ciencyfi ofHTS-based SMES may make it a contender for the storagetechnology needed to complement intermittent sources likesolar andr windd farms.d
Please visit 10.1557/mrs.2012.205t for ar supplementarya tableon selected high-temperatured superconductor utilityr projects.
The Long Island Power Authority has been operating, since 2008, acable system manufactured by Nexans that utilizes AMSC’s high-temperature superconductor wire and an Air Liquide cooling system.Energized in April 2008, this is the world’s firstfi superconductortransmission voltage cable system, which is capable of transmittingfup to 574 MW of electricityf and powering 300,000 homes. Photocourtesy ofy AMSC.f
MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin • Energy Quarterly
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David Eaglesham is dedicated to using materials science to address energy problems. After
earning a PhD degree in physics at the University of Bristol (UK), he spent many years at
Bell Laboratories working on semiconductors and later took on management positions at
Lawrence Livermore National Laboratory and Applied Materials. It was at Applied Materials
that he began to connect with the solar industry, just as it was getting hot. When he joined
First Solar in 2006 as Vice President of Technology, it had around 350 employees and about
USD$50 million in revenue. The company now has grown to about USD$4 billion in revenue.
With an extensive portfolio of achievements in scientificfi research and ever eager for new
challenges, Eaglesham left First Solar this summer and has taken a new position with Mg-ion
battery leader Pellion Technologies. We caught up with Eaglesham at a corner brewery in
Ypsilanti, Mich., where we noticed that they were putting up photovoltaic panels on the roof
combined with a solar thermal energy system—a hybrid system. This auspicious beginning
led to an all-encompassing interview spanning the range from materials research to mitigating
global warming.
MRS BULLETINS :NN Several years agowhen you were president of thef Mate-rials Research Society, you called fora “Manhattan Project” for renewablerenergy. Is this still needed?DAVID EAGLESHAM: I think wekneed tod make carefully targeted invest-dments in basic research—that’s actu-ally something that thet governmentdoes very well. And Id think govern-kment investmentst in creating marketscan help to build ad marketplace inwhich all commercial sectors can thencompete without furthert governmentrinvolvement. And, I believe that ast aplanet, we will eventually put at priceon carbon—a carbon tax. The countriesthat aret firstfi tot implement sucht a taxwill be the fi rstfi tot develop low-carbon
technologies and willd ultimately be themost competitive.t
Where are the biggest areas of op-fportunity for materialsr in improvingphotovoltaic (PV) effiff ciencyfi and inreducing cost?With regard tod materials, it’s hard todcome up with a truly new semiconduc-tor becauser photovoltaic (PV) materi-als like cadmium telluride (CdTe) andcopper indiumr selenide (CIS) are goodby virtue of theirf defectr properties.t Inparticular, the recombination velocityat dislocationst and graind boundaries islow. And thatd makest predicting goodnew materials diffiff cult.fi As a result,a lot oft peoplef are working on thewrong problem. The big opportunities
that It see lie in exploiting capabili-ties that thet semiconductor andr LEDd[light-emitting diodes] industries havedeveloped tod achieve higher efr fiff cien-ficies in silicon and otherd materials—rtechnologies like heterojunctions,band engineering,d heteroepitaxy,dopant engineering,t barrier layers,r andcontact engineering.t Figuring out howtto adapt thoset tricks to photovoltaicsin an affordable way while achievinghigh throughputs presents a huge op-portunity. Other majorr PVr challengesVare around metrologies,d control ofthe process, and manufacturability,dand that’sd an area where the materialscommunity excels.
You said a lot of peoplef are workingon the wrong problem. What’s thewrong problem?There’s a big push to try to use earth-abundant elementst in semiconductors,but it’st hard tod findfi somethingd that’smuch rarer thanr tellurium, and indCdTe, only a tiny fraction of thef totalcost oft thef system is the tellurium.Similarly, the affordability of silverf isrnot at problem in crystalline silicon.So we’re trying to fixfi something thatisn’t at problem. What wet really wantis higher efr fiff ciency.fi
Where can materials help promotesustainable, long-term signifi cantfiPV powerV production?r
From materials research to climate change: David Eaglesham assessesthe solar energy industryInterviewed by Steve M. Yalisoveand Arthur L. Robinson
Steve M. Yalisove, University of MichiganArthur L. Robinson, [email protected]
MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin • Energy Quarterly
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wI think there’sk going to be sustainable,long-term silicon power productionrwithout goingt beyond thed existingmaterials technology. And ongo-ding improvement oft thef existing thinfilms,fi CdTe and CIS,d will continue tomake them successful. But theret arethings we could dod to move the currenttechnology landscape faster. Cad-mium telluride is the technology that’sfarthest fromt its theoretical capability,so there’s plenty of roomf for raisingr theeffiff ciency.fi In other materials,r produc-ing a low-defect densityt III–V onV glasseither byr heteroepitaxy or byr liftofftechniques would resultd int a very higheffiff ciencyfi device, as would goodd defectdpassivation. Tandem devices are cur-rently under- or unexploitedr andd willdbe a major directionr in the future.Organic devices are problematicbecause there’s still a question whethersomeone can produce a reliable deviceat ant effiff ciencyfi that’s high enough tomake a difference.
What about the vision of paintingf asolar cellr on the side of af wall? Mightorganics be a part of that?fThe notion ofn sprayingf on PVn isVseductive but delusional:t even ifn wefcould figurefi out encapsulation,t there’sstill wiring, mounting, inverters. And Iddon’t knowt howw we’llw test thet device forreliability. Rolling out flexiblefl devicesonto a roofa mayf bey more practical, andthe materials community willy figurefiout howt tow make the installation cost-neffective, which ish the biggest costt oft thefsystem. The fl exiblefl device is not neces-tsarily any organicn device. Whatever itr is,twe’d stilld choose the materials systemthat providest the highest eft fiff ciencyfi inyorder tor lower ther biggest cost.t
What challenges would we face ifwe wanted to get to even 1% of thefglobal energy production with PV?I think thek existing technologies andsome of thef emerging ones can take usmost oft thef way. There’s good reasond tobelieve that at cost oft electricityf around10 cents/kilowatt-hour isr reachable, andthat makest the economic impact oft afcarbon tax affordable. There’s a lot oft
fear thatr at carbon taxwill make the economygrind tod a screaminghalt. But thet differencebetween fossil and PVdelectricity is only about4 cents/kilowatt-hour,and thatd meanst that thettax is affordable.
Another arear wherewe can make headwayis in the “balance-of-systems” cost throughthigher efr fiff ciencyfi[solar cells]r and betterd constructionrpractices. New materials for powerrelectronics are likely to have a bigimpact, but lifetimet is an issue.
Many say that solar, as a signifi cantfienergy provider, is a non-starteruntil storage solutions become eitherbetter orr cheaper.r Do you agree?I believe that renewablest can and willdplay a large and successfuld role atthe grid leveld without storage.t Sincedemand ind any industrial country peaksin the middle of thef day, we can beginby adding solar tor the grid basicallyd asnegative demand duringd peak hours.kSecond, as solar-energy productionforecasting becomes better, we canuse PV asV a predictable component oftour generatingr “mix,” and ultimately,dwe can add wind,d which primarilygenerates energy during the night.Studies show we can achieve very highpenetration of renewablesf into the gridat thet expense of fossil-fuelf sourceswithout storage.t On the other hand,rthere’s a clear pathwayr for hybridsrto decrease the carbon footprint ofttransportation through improved stor-dage solutions, and thisd direction is anextremely interesting path for materialsrinnovation.
The solar industryr is in fl uxfl withIPOs and venture-capital cash infu-sions mixing with production scale-backs and business closings. Whatare the reasons for thisr shakeup?And how does it affect the prospectsof af solution to climate change?This industry exists for regulatoryr
reasons, and recentlyd regulators havechosen to make the PV marketV smaller,tresulting in lower capacity,r lowerprices, a collapse in stock prices,k andbankruptcy for noncompetitiver players.I think thek regulators got prettyt muchthe outcome they wanted: a much morecompetitive and lessd profitablefi solarsector thatr ist serving a significantlyfismaller market.r I think thek underlyingquestion is whether ther shakeup meansthat thet industry is closer tor or fartherrfrom the long-term goal of makingfsolar electricityr competitive with fossilfuels, and clearlyd the industry is muchcloser tor that goalt than it was.t
Regarding climate change, a com-petitive industry is not enough.t Peopleassume that allt we need ared renewabletechnologies that aret competitive withfossil fuels, and thed free market willt doits work. That’s delusional on three dif-ferent levels.t First, no energy marketanywhere in the world isd really com-petitive. Second, where renewables arenow competitive with fossil fuels, asin India, fossils are subsidized. Last, ifPVs were ultimately successful, peoplewould justd uset more electricity, andwe haven’t solvedt anything.d It’s aboutchoosing how we tax. Right now,t mosttax is income tax, so we’re taxinglabor asr opposed tod taxing more evenlyacross fossil-fuel consumption andlabor. If wef want tot import energyt andexport jobs,t we can keep 100% of theftax burden on labor. If wef want tot re-duce the use of fossilf fuels, we have tomake them more expensive. We haveto have a carbon tax. It’s that simple.t
MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin • Energy Quarterly
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Super-capacitors take charge in GermanyBy Philip BallFeature Editor Yury Gogotsiy
The yellow-and-white Stadtbahntrams criss-crossing the streets of
Mannheim in southern Germany lookunremarkable, but somet of themf are lit-erally carrying what couldt bed the key togreener publicr transportation. The elec-trically powered vehicles use 30% lessenergy than their equivalents in mostother cities because they contain on-board systems for capturingr the energythat wouldt otherwised be squandered whendthe trams brake. This energy is convertedinto electricity, which is then stored indevices called supercapacitorsd mountedon the tram roof.
Supercapacitors are power-storagedevices that can supply onboard elec-trical power inr hybrid vehicles. Unlikebatteries, supercapacitors can be chargedand dischargedd ind seconds and cand with-stand many hundreds of thousandsf ofsuch charging cycles. This makes themideal for energy-savingr applications thatcapitalize on transient opportunitiest forrecharging, such as energy capture dur-ing braking, and thatd requiret power tor bedelivered ind short burstst of perhapsf halfa minute or less.r They can, for example,r
help with acceleration or canr restart en-tgines that cutt outt tot reduce fuel use andpollution in stop-and-go traffiff c.fi
Whereas batteries store energy inchemical form—in substances that canreact tot release electrical energy—capac-itors store it byt simply piling up electri-cal charge on two electrodes. The largerthe electrodes and the closer they are,the more energy that cant be stored. Anordinary capacitor consistsr of twof con-ductive plates separated byd an insulating(dielectric) layer. But a supercapacitor(sometimes called an ultracapacitor)holds its charge a little differently. Typi-cally it containst two conductive porouselectrodes—usually made of carbon—fimmersed in a liquid electrolyte andseparated byd a very thin insulating fi lm,fiusually made of af porous polymer. Thecharge is stored by adsorption of ionsfonto the high-surface-area electrodes.When the electrodes are charged, thisproduces a layer ofr oppositelyf chargedions on their surfaces:r a so-calleda electri-dcal double-layer, which is why this typeof supercapacitorf isr often calledn ad double-alayer capacitor.r
The potential of supercapacitorsf to as-sist int powering vehicles was displayedin dramatic fashion in the 24-hour speedrrace at Let Mans this June, when Toyotafieldedfi a hybrid TS030 that used themfor energy-capturer during braking. Thedevices performed perfectly,d but at crashscuppered thed vehicle’s bid ford glory.r
The Mannheim trams are rather morersedate, but witht their ownr onboard pow-der, they can keep running across shortgaps or disruptionsr in the electricity line,for example due to ice or where over-head powerd linesr cannot bet deployed fordaesthetic or technical reasons. The en-ergy source can also be tapped tod driveair conditioning,r automatic windows, orpassenger doors.r
These trams have been reapingn the ben-efi tsfi of supercapacitorsf since 2003 andare now joined byd a host oft otherf public-rtransportation systems in Germany andbeyond. Supercapacitor technology isdeployed, for example,r on Spanish and
French trains and hybridd busesd all overthe world, on construction equipmentsuch ash cranes, and ond garbage-collectionntrucks. On buses, it cant reduce the effec-tive carbon-dioxide emissions by around30%, while the Munich-based heavy-ve-dhicle manufacturer MANr estimated thatdtheir supercapacitor-r fittedfi coachesd eachsave around $4,500d a year onr fuel costs.
Reducing fuel consumption and emis-dsions during the “dead time”d of standingfat stops,t intersections, and trafd fiff cfi lights isa particularlya pressing concern for buses.rSince 2001, MAN has been developinghybrid supercapacitor buses called theLion’s City Hybrid. The current com-mercial model, available since 2010,cuts diesel consumption by up to 30%,and isd now being used ond a small scalein Paris and somed other Europeanr cities.In principle, buses can recharge their su-rpercapacitors not justt duringt braking, butalso at everyt bus stop by making contactwith overhead charging lines for justr afew seconds.
So far ther take-up of thef technologyhas been relatively modest. But itt lookstset tot expand bothd as energy-saving andlow-emission technologiesn become moreimperative and asd the technical capabili-ties of supercapacitorsf improve. Super-capacitors are not byt any means a pana-cea for greenr transportation: they have alower totalr energy density than batteriesby one or twor orders of magnitude,f forexample. But theyt have a higher powerrdensity, delivering much more powerover ar short periodt ofd time.f
“There is no single perfect energy-storage solution, no ‘one size fi tsfi all,’”said materialsd scientist Yuryt Gogotsi atDrexel University in Philadelphia. “A‘battery of thef future’ may be a battery-supercapacitor hybrid having the longlifetime, fast charging, and highd powerof af supercapacitora combinedr withd ah highaenergy density of af battery.”
The main producersn of supercapacitorsfworldwide are Nesscap Energy, based indSouth Korea, and the California-basedcompany Maxwell Technologies. Theseand otherd manufacturersr supply the basic
MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin • Energy Quarterly
cells to companies such as Siemens andthe Belgian firmfi 4Esys, which incorpo-rate them into modules that cant be addeddirectly intoy vehicle designs. In Germany,nthe electrical-component manufacturerWIMA inA Mannheim, which special-izes in capacitors and supercapacitors,manufactures both individual cells andmodules. Siemens has developed twoenergy-storage supercapacitor modulesrcalled Sibacd and Sitrac,d which are incor-porated intod the vehicles or ther power-supply lines respectively to capture ener-gy duringy braking. Sitras can alson be usedto maintain the voltage of thef networkduring peaks of highf power demandr ordtemporary outages.
Despite the promise of supercapacitorsfin transportation, their uptaker has beenrather slow and cautious over the pastdecade. “There have been an lota oft projectsfwhere prototypes are tested overd ar con-siderable time,” said Frank Herrmann,an engineer atr WIMA.t The market has,thowever, been picking up speed overd therpast two or threer years, partly becauseof risingf fuel costs. “The economics aredriving it,” said Juergen Auer ofr Ness-fcap’s division in Schondorf, Germany.“It’s very sensitive to what happens todiesel prices.”
And although Germany is noted forits commitment to green energy poli-cies, the kind of supportf from central
government that has been enjoyed by,say, photovoltaic energy (where subsi-dies and guaranteesd of competitivef rateshave boosted production and use) hasnot beent extended tod the supercapacitormarket. “German authorities are prettyconservative,” Auer feels.r There are alsono coherent planst for howr and whered thetechnology might bet introduced. “Eachenergy ory transportr companyt hasy a hybridasolution, whether withr supercapacitorsh orbatteries,” he said, “but thet finalfi custom-ers like cities aren’t readyt to buy it ort im-rplement itt intot their fl eets.fl That makest ita very diffiff cultfi productt tot market.” Auercontrasts this ruefully with China, whereefforts to use supercapacitors in transportn
began only about fourtyears ago but havet re-sulted already in tensof thousandsf of “super-fcap” buses on the road,especially in Shanghai.n“Right nowt the biggestmarket is in China,”Herrmann agreed.
However, Herrmannthinks that Germany’stenergy policy to userenewable rather thannuclear energyr will in-directly help the tech-nology. Offshore windfarms, for example,need regular mainte-nance using ships andhelicopters, and super-dcapacitors should helpd
to reduce the running costs of thesef fl eets.flGermany’s federal system offersm scope
for regionalr projects, and individuald cit-ies such as Mannheim have sometimeslaunched theird ownr initiatives. Siemens’Combino trams, which use the Sibacsystem, have been deployed in severalGerman cities,n including Augsburg, Düs-seldorf, Ulm, and Potsdam, as well asoutside Germany in Amsterdam, Basel,and Budapest for example. The com-pany unveiled ad second-generation tramsystem, called Avenio,d last year.t Mean-while, the Mannheim trams use the Mi-trac supercapacitor systemr produced bydthe Berlin-based company BombardierTransportation. Last year, the German
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etransport operator RNV, which servesthe Rhein-Neckar region and includesMannheim, Heidelberg, and Ludwig-shafen, ordered 11 more Bombardiertrams for itsr 200-km network.
In part, the obstacles to wider user arematters of infrastructuref and design:engineers are more used to thinking interms of hybridf vehicles with batteriesthat require charging cycles of severalfhours, rather than the several secondsneeded byd supercapacitors. But ast theiruse hinges mostly on economics, it ist vi-tal to improve performance while reduc-ing costs. Supercapacitors can have animpressive lifetime—15 to 20 years—butthe initial outlay is still rather high.r
A keyA problem is that the individualcells develop relatively low voltages—typically less than 3 V—because of theflimited electrolyted stability. This meansthat tot obtain the 24 V typicallyV neededfor vehicler systems, several cells must betconnected ind series,n making for relativelyrcostly and bulkyd modules. “We need todincrease voltage per cellr in order tor havehigher energyr density and fewerd cells,”rsaid Herrmann.d
Auer said that some of thef raw ma-terials, such as the porous carbon elec-trodes, are also somewhat costly,t and sodis the manufacturing process. However,Gogotsi insists that “there is no funda-mental reason for supercapacitorsr to beexpensive, because they use just carbon,tpolymer film,fi an inexpensive aluminumfoil, and an organic electrolyte, withno rare or expensive elements.” Costsshould fall, for example,r simply as thescale of productionf increases and manu-dfacturing methods improve. That wouldtnot only boost current uses but enablenew applications to emerge.
This all leaves Auer optimisticr aboutthe prospects. “There’s still a lot oft roomffor futurer growth,” he said. “There arepotential uses everywhere.” He said thatdsupercapacitors are one of thef few elec-tronic components that havet had ad steadi-aly growing market overt recentr years.t
“It takest time,” he said.
Trams in Germany powered by supercapacitors use 30% lessenergy than their equivalents in other regions. Credit: RNV
MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin • Energy Quarterly
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ENERGYFOCUS
Tim Palucka
Dielectric core–shell optical antennas can enhancen the trappingof solarf radiationr inn photovoltaicn devices, enabling a 70-nm-athick a-Si:Hk thin filmfi to absorb about ast much radiation asa typicala 400-nm-thick anti-rek fl ectionfl coating thin fi lm.fi Thestructures tested usedd semiconductingd a-Si:H as the core anddielectric materials such ash ZnO and Sid 3N4 as the shell. LinyouCao of Northf Carolinah Statea University andy A.d Paul Alivisatosat thet University ofy California,f Berkeley, and theird colleaguesrreported ind Nano Letters that thet solar radiationr absorptionenhancement comest from multiplicationm ofn contributionsf fromleaky modey resonances in then semiconductor andr anti-red fl ectionfleffects in then dielectric. The size ratio of thef core and shelld is thekey toy optimal absorption. After optimizingr the dielectric shellfor anti-rer flection,fl sizing the semiconductor corer at at 0.5–0.6acore–shell ratio preserves the intrinsic leaky modey resonances.This technology couldy leadd tod thin solarn cellsr with improvedhconversion efn fiff cienciesfi and lowerd costr thant currentlyn availableysolar cells.r
Thinner solar cells use dielectric core–shelloptical antennasNano Lett.o DOI: 10.1021/nl301435r
By studying the morphology and crystald structure of lithium-fsulfur (Li-S)r batteries during operation, researchers at StanfordtUniversity led byd Michael Toney have discovered phenomenadthat largelyt contradicty previoust ex situx studies. Sulfur hasr greatpromise as a cathode in this system because of itsf high energydensity and lowd cost. However, Li-S batteries fail after onlyr afew tens of cycles,f compared tod thousands for Li-ionr batteries.nPrevious ex situ studies have attributed thed short lifetimet tothe dissolved sulfurd formingr electrically insulating crystallineLi2S following discharge and tod sulfur’s failure to recrystallizeat thet cathode following charging. Now, using in operandosynchrotron-based XRDd and transmissiond x-ray microscopy,Toney and colleagues have shown that no crystalline Li2Sforms; they speculatey that int previousn studies, it wast an artifactnof thef ex situ XRD process. Furthermore, recrystallization ofsulfur canr occur dependingr on the cathode morphology. Theyconcluded thatd in operando studies are necessary for furtherrevaluation of sulfurf cathodesr for Li-Sr batteries.
Study clarifi es short Li-S battery lifetimeJ. Am. Chem. Soc. DOI: 10.1021/ja2121926
Transparent nanogenerators use triboelectric effectNano Lett.o DOI: 10.1021/nl300988z
Flexible transparent nanogenerators (FTNGs) based ontriboelectric phenomena could be used as self-poweredsystems for touchscreensr in electronic displays according toresearch done by Zhong Lin Wang of thef Georgia Instituteof Technologyf and co-workers from Xiamen University,China. The triboelectric effect referst to electrificationfi resultingnfrom frictional contact between materials. The FTNGsuse only transparent materials, including a patternedpolydimethylsiloxane (PDMS) thin filmfi sandwiched betweendtwo sheets of polyester,f each capped with an indium tinoxide electrode. The 460-micron-thick devicesk with an area
of 5.4f cm2 produced upd to 18 V ofVelectricity at a current density ofapproximately 0.13 A/cm2 whenfl exed,fl yielding 0.7 A ofA currentf(up to ~13 W ofW power)f at at fl exingflfrequency of 1f Hz. The researchersfabricated PDMS thin filmsfi withlinear, cubic, and pyramidald patternsto increase friction during bending.As reported in Nano Letters, the
triboelectric effect was greatest in devices with pyramidalpatterns, followed byd the cubic, linear, and flatfl PDMSt sheetsin decreasing order.
Artifi cial enzyme could enhancebiofuel production
The Plante Cellt DOI:l 10.1105/tpc.112
Lignin, the tough biopolymer inr plant cell walls that givesthem structural strength, presents significant difficultieswhen trying to convert biomass to biofuels; it interferes
with digestive enzymes thatmust access the sugars insidethe plants to produce thesefuels. Now, using mutagenesisto create an artificial enzymethat inhibits the polymerizationof threef lignin precursors calledmonolignols, researchers atBrookhaven National Laboratoryand thed University of Wisconsin,fMadison, have developed amethod of reducingf the amountof ligninf in Arabidopsis plantsby up to 24 percent withoutcompromising the growth of thef
plants. As reported ind then July 31y edition ofn The Plant Cell,t thisdevelopment couldt signid ficantlyfi reduce the cost oft biofuelsfby removing pretreatment stepst that aret currently needed todreduce lignin content int industrial biofuel processes.
Introduction personal journey in nanowire research started withd Profes-
sor Charlesr Lieber atr Harvardt University,d where I investigated
fluxfl line pinning in highn TcTT superconductors using nanowires as
pinning centers. More than 15 years later, I devote most oft myf
efforts in studying these nanostructures for energyr conversion
and storaged purposes.
I would like to acknowledge the pioneering contribution
of R.S.f Wagner atr Bell Laboratories. Much of ourf nanowirer
research today relies on the very powerful method developedd
by Wagner, known as the “vapor-liquid-solid process”d (VLS).1
In 1964, Wagner describedr thed VLS growth of siliconf micro-
and nanoscaled wires or whiskersr and pointedd outd thatt onet of
the catalysts that cant be used isd gold. Gold isd often used todayd
to grow silicon nanowires, as well as copper, nickel, and, more
recently, aluminum. Wagner alsor noted thatd nanowirest can grown
into different crosst directions. Over ther past 10t years, there have
been thousands of papersf on silicon nanowire growth, growth
direction control, and the use of differentf catalysts and sub-
strates, all based ond Wagner’sn original concept.2 Wagner’s work
in the 1960s set thet foundation for muchr of today’sf nanowire
research.
My firstfi nanowire experiments were in the early 1990s,
when manyn ofy usf were still working on high-Tn cTT superconductors
(HTSC). The subject oft myf PhD thesis was to fi ndfi ad way to
introduce linear defectsr within high-temperature superconduc-
tors, in the hope of increasingf the critical current density.t Our
approach was to introduce single-crystalline nanowires into a
high-TcTT cuprate superconductor tor make a composite, to create
stable linear tracks,r and tod increase the critical current densityt
by “pinning” the fluxfl lines.3 This work paralleledk muchd of thef
work conductedk atd thet time using fast iont irradiation to create
linear defectsr within high-temperature superconductors. That
was the start oft myf research in this very exciting area, and itd
Semiconductor nanowire building blocks: From fl ux line pinning to artifi cial photosynthesis
Yang
The following articleg is an edited transcriptd oft thef MRS MedalS Lecturel presented byd Peidong Yangg ong
November 30,r 2011 at thet 2011 Materials Research Society Fall Meetingl ing Boston. The MRS MedalS isl
awarded ford ar specificfi outstanding recentg discoveryt or advancementr thatt hast a major impactr ont the
progress of af materials-related fid eld.fi Yang receivedg thed award ford “outstandingr contributionsg in the
creative synthesis and assemblyd of semiconductorf nanowiresr and theird heterostructures,r and innovationsd
in nanowire-based photonics,d thermoelectrics, solar energyr conversion, and nanofld uidicflfl applications.”
Semiconductor nanowires,r by defiy nition,fi typically havey nanoscale cross-sectional dimensions,
with lengths spanning from hundreds of nanometersf to millimeters. These subwavelength
structures represent a new class of semiconductorf materialsr for investigatingr light generation,
propagation, detection, amplification,fi and modulation. After more than a decade of
research, nanowires can now be synthesized and assembled with specificfi compositions,
heterojunctions, and architectures. This has led to a host of nanowiref photonic and electronic
devices, including photodetectors, chemical and gas sensors, waveguides, LEDs, microcavity
lasers, and nonlinear optical converters. Nanowires also represent an important class of
nanostructure building blocks for photovoltaics as well as direct solar-to-fuel conversion
because of theirf high surface area, tunable bandgap, and efficientfi charge transport and
collection. This article gives a brief historyf of nanowiref research for the past two decades
and highlights several recent examples in our lab using semiconductor nanowires and their
heterostructures for the purpose of solarf energy harvesting and waste heat recovery.
Peidong Yang, Departments of Chemistry,y and Materials Science and Engineering , Lawrence Berkeley National Laboratory; [email protected] DOI: 10.1557/mrs.2012.200
SEMICONDUCTOR NANOWIRE BUILDING BLOCKS: FROM FLUX LINE PINNING TO ARTIFICIAL PHOTOSYNTHESIS
807MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
was also the beginning of nanowire research
in Lieber’s group. Shortly after, the landmark
paper by Morales and Lieber (1998) 4 introduced
the laser ablation method for the growth of
silicon nanowires, once again based on the VLS
process. In this case, the vapor was generated
using laser ablation. After that, there was sig-
nifi cant research using VLS processes to grow
semiconductor nanostructures of many different
compositions. Many different vapor deposition
methods were employed, including chemical
vapor deposition (CVD) and several physical
vapor deposition techniques.
After joining the University of California,
Berkeley faculty in 1999, my fi rst research
effort was to investigate the growth mechanism
of semiconductor nanowires. Initially, we tried
to explore in situ growth of Ge nanowires; we
observed the process of VLS growth using an
in situ high temperature transmission electron microscope
(TEM);5 in this case we were investigating the nucleation of a
Ge nanowire, using a gold nanoparticle heated to 800o C as the
catalyst. Based on the Au-Ge phase diagram, at 800 o C, we can
fi rst observe an alloying process that leads to the liquid forma-
tion; with more Ge vapor incorporation, the system eventually
moves into a biphasic region, and we can observe the nucleation
event in real time. The creation of this solid-liquid interface
is the starting point for one-dimensional crystal growth; this
underpins the fundamental nucleation step at the nanometer
scale for all of the VLS processes.
In the 1990s, there were very few papers published in
the semiconductor nanowire fi eld, but there has been a rapid
increase in the past 10 years, and nowadays there are thousands
of papers published every year on this subject, with hundreds of
research groups now active in this exciting area.
Nanophotonics In the last decade, we have seen many important
discoveries in a couple of different directions,
such as nanoelectronics and photonics, and
next I will describe some of the work we did
in these areas. In 2000, we discovered that a
single-crystalline semiconductor nanowire can
serve as a nanoscopic laser cavity ( Figure 1). 6
This is basically a Fabry – Pérot cavity, and
Figure 1b shows the far-fi eld emission patterns
from single nanowires, the power-dependent
laser spectra from these individual nanowires,
and the integrated intensity as a function of the
incident power. For the last couple of years,
we have extended our work on photonics from
nanolasers to subwavelength waveguides, as
well as using a single nanowire to perform
nonlinear optical mixing. 7,8 Due to the high
refractive index of these nanostructures, we can
achieve these functionalities either in air or in a liquid. 9 This is
quite powerful, as we have basically developed a nanoscopic
light source that can be potentially used in a liquid medium.
Recently, we have been trying to utilize these nanoscopic
light sources for endoscopy at the single living cell level. 10
We attached a single nanowire onto an optical fi ber so that
we could deliver light directly to the nanowire waveguide and
then use the waveguided end emission to perform imaging at
the single-cell level. These nanowires are very robust, do not
fracture easily, and can be bent, so they are stable enough to be
used in single-cell endoscopy. As illustrated in Figure 2 , the
nanowire had quantum dots attached to the surface that were
cleaved by UV light. After cleaving, the quantum dots were
delivered to a single cell. As an example, we can deliver the
quantum dots into the cytoplasm and directly to the nucleus. It is
Figure 1. Nanowire nanolasers. (a) Schematic of an optically pumped nanowire laser
cavity. (b) Lasing spectra from an individual nanowire cavity, a far-fi eld optical image of a
lasing 30- μm-long GaN nanowire (left inset), and power dependent curve for the nanowire
be placed in between. We can now make two-inch diameter discs
by laminating two layers of nanowire materials together, for
example, a WO 3 or TiO 2 nanowire mesh on top and a GaP
nanowire mesh underneath, where one is the photocathode
and one is the photoanode. Of course the bandgap and photo-
current output do not match at this point. We are trying to use
this as a model system to demonstrate whether such a bilayer
nanowire fabric idea can work. The initial results are promising.
The main problem right now is the urgent need to discover
better anode materials to replace TiO2 or WO3. Above all, we
believe that these high surface area semiconductor nanowires,
with their high carrier mobilities, will eventually be part of the
artifi cial photosynthesis system as these nanostructures enable the
stacking of the catalysts in the third dimension,
and effectively relax the stringent requirements
for catalysts with high turnover frequency.
Summary Over the past 10 years, we have continued to
develop the science and technology of semi-
conductor nanowires. As of today, nanowires
with different sizes, growth directions, com-
positions, and heterojunctions can be rationally
designed, synthesized, and assembled. We have
already seen major progress in many different
areas of nanowire research (e.g., electronics,
photonics); we can be confi dent that we will
continue to see many more fundamental new
discoveries and science based on this unique
class of nanoscale building blocks. Considering
their unique structural, optical, and electrical
properties, we expect that these nanostructures
will have a signifi cant impact on large scale
clean energy conversion and storage technolo-
gies. In the meantime, the future of nanowire
technology will be largely dependent on how
well we can balance the issues of cost, perfor-
mance, and stability of nanowire-based devices
and systems.
Acknowledgments I wish to thank my research group for their hard
work. I would also like to acknowledge the
generous continued support from the Depart-
ment of Energy, Offi ce of Basic Energy Sciences
over the last 10 years, without which much of
the progress I discussed would be impossible.
References 1. R.S. Wagner , W.C. Ellis , Appl. Phys. Lett. 4 , 89 ( 1964 ). 2. Y.N. Xia , P.D. Yang , Y.G. Sun , Adv. Mater. 15, 353 ( 2003 ). 3. P. Yang , C.M. Lieber , Sciencee 273, 1836 ( 1996 ). 4. A.M. Morales , C.M. Lieber , Sciencee 279 , 208 ( 1998 ).5. Y. Wu , P. Yang , J. Am. Chem. Soc. 123, 3165 ( 2001 ). 6. M. Huang , S. Mao , H. Feick , H. Yan , Y. Wu , H. Kind , E. Weber , R. Russo , P. Yang , Sciencee 292, 1897 ( 2001 ).7. M. Law , D. Sirbuly , J. Johnson , J. Goldberger , R. Saykally ,
P. Yang , Sciencee 305 , 1269 ( 2004 ). 8. Y. Nakayama , P.J. Pauzauskie , A. Radenovic , R.M. Onorato , R.J. Saykally , J. Liphardt , P. Yang , Naturee 447, 1908 ( 2007 ). 9. D.J. Sirbuly , M. Law , P. Pauzauskie , H. Yan , A.V. Maslov , K. Knudsen , R.J. Saykally , P. Yang , PNASS 102, 7800 ( 2005 ). 10. R. Yan , J. Park , Y. Choi , C. Heo , S. Yang , L.P. Lee , P. Yang , Nat. Nanotechnol.7 , 191 ( 2012 ). 11. D. Li , Y. Wu , P. Kim , L. Shi , N. Mingo , Y. Liu , P. Yang , A. Majumdar , Appl. Phys. Lett. 83 , 2934 ( 2003 ). 12. A.I. Hochbaum , R. Chen , R.D. Delgado , W. Liang , E.C. Garnett , M. Najarian , A. Majumdar , P. Yang , Naturee 451, 163 ( 2008 ). 13. M. Law , L. Greene , J.C. Johnson , R.J. Saykally , P. Yang , Nat. Mater. 4 , 455( 2005 ). 14. J. Tang , Z. Huo , S. Brittman , H. Gao , P. Yang , Nat. Nanotechnol. 6, 568 ( 2011 ). 15. A. Fujishima , K. Honda , Naturee 238 , 37 ( 1972 ).16. A.J. Nozik , Appl. Phys. Lett. 30, 567 ( 1977 ). 17. J. Sun , C. Liu , P. Yang , J. Am. Chem. Soc. 133, 19306 ( 2011 ).
Size-controlled nano particles – 1– nm to 30 nm dia.
Dense filmfi formation without process gas
Small target size: 10 mm dia. x 17 mm
Uniformity +/- 10% over 50 mm diametercoated area
Nano Particlesand Coatings
18. A. Kay,y I. Cesar,r M. Grätzel , J. Am. Chem. Soc. 128, 15717 (2006). 19. T. Kuykendall , P. Ulrich , S. Aloni, P. Yang, Nat. Mater. 6, 951 (2007).20. C. Liu, Y. Hwang, H.E. Jeong, P. Yang, Nano Lett.o 11 , 3755 (2011). 21. Y. Hwang, C. Wu , C. Hahn, H. Jeong , P. Yang , Nano. Lett. 12, 1678 ( 2012 ). 22. E. Garnett , P. Yang , Nano Lett.o 10, 1082 ( 2010 ). 23. D.J. Sirbuly,y M. Law, H. Yan, P. Yang, J. Phys. Chem. B 109 , 15190( 2005 ).
Peidong Yang is a professor inr the Department ofChemistry, Materials Science and Engineering,the S.K. and Angela Chan Distinguished Chairin Energy, and a senior faculty scientist at theLawrence Berkeley National Laboratory (LBNL).He received a BS degree in chemistry from theUniversity of Science and Technology of China(1993) and a PhD degree in chemistry fromHarvard University (1997). His postdoctoralresearch was at the University of California, SantaBarbara, after which he joined the Departmentof Chemistry faculty at the University ofCalifornia, Berkeley (1999). He founded thenanoscience subdivision within the American
Chemical Society (ACS) and also co-founded two startups, Nanosys Inc. andAlphabet Energy Inc. In addition, he is an associate editor for the Journal ofl thefAmerican Chemicaln Societyl andy serves on the editorial advisory boards for anumber of journals, including Accounts ofs Chemicalf Researchl andh Nano Letterso .sHis main research interest is in the area of one-dimensional semiconductornanostructures and their applications in nanophotonics and energy conversion.Yang is the recipient of numerous awards and recognitions. He can be reachedat the Department of Chemistry, University of California, Berkeley, MaterialsScience Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720,USA; email [email protected].
Hybrid cell for simultaneously harvesting multiple types of energies Our environment has an abundance of energy
forms, including light, thermal, mechanical (such
as vibration, sonic waves, wind), magnetic, chem-
ical, and biological. Harvesting these types of
energies is of critical importance for long-term
energy needs and sustainable development.
Innovative approaches have to be developed
for conjunctional harvesting of multiple types of
energies using an integrated structure/material so
that the energy resources can be effectively and
complimentarily utilized whenever and wherever
one or all of them are available. We initiated an idea
in 2009 for harvesting multiple types of energy
using a single device structure, known as a hybrid
cell (HC) ( Figure 7a).36 The structure is based
on vertical ZnO NW arrays but with the addi-
tion of a solid electrolyte and a metal coating. 37
The solar cell open circuit voltage ( UOC-SCUU ) was
Figure 5. Fabrication of a high output nanogenerator using vertically aligned nanowire
arrays/fi lms grown on two sides of a polymer fi lm. (a) Fabrication process of the nanogenerator.
The lower right part is a photo of a fabricated nanogenerator after packaging. The
bending of the nanogenerator shows good mechanical fl exibility. (b) Output current
and (c) output voltage of a typical nanogenerator.31
Figure 6. (a) Schematic diagram of an integrated self-powered system that can be divided
into fi ve modules: energy harvester, energy storage, sensors, data processor and controller,
and data transmitter and receiver. (b) The voltage sequence used to trigger the sensor,
representing a waveform envelope of the input signal. (c) Recorded signal from the
headphone jack of the radio located 10 m away, showing the technical feasibility of a
wireless self-powered system. 34, 35
FROM NANOGENERATORS TO PIEZOTRONICS—A DECADE-LONG STUDY OF ZNO NANOSTRUCTURES
819MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
0.42 V, and the short circuit current density (J SC-SCJJ ) was
0.25 mA cm –2 . The NG was characterized by introducing
ultrasonic waves through a water medium without sun-
light illumination; the corresponding J–V curve shows that V
UOC-NGUU was ∼0.019 V, and INGII was ∼0.3 pA cm –2. When
only simulated sunlight shines on the HC, the dye-sensitized
solar cell (DSSC) worked ( Figure 7b ), and the optimum
output power density was found to be 32.5 μ Wcm–2 at
JSCJJ = 140 μ Acm–2mm and UOCUU = 0.231 V. When both the DSSC and
NG were simultaneously operating in series, the corresponding
output power density was 34.5 μ Wcm –2mm at J SCJJ = 141 μ Acm –2mm and
UOCUU = 0.243 V. After the ultrasonic wave was turned on, power
density increased (∆PHC ) by 2 μ Wcm –2mm , which represented more
than a 6% enhancement in optimum power output. Therefore,
in addition to enhancing the open circuit voltage, the HC suc-
cessfully added the total optimum power outputs from both the
solar cell and the NG.
With the development of modern medical technology, pow-
ering implantable nanodevices for biosensing using energy
harvesting technology has become a challenge. We developed
a HC for harvesting mechanical and biochemical energies 38
mainly for biomedical applications. The structure is based on
an integrated NW-based NG system and an enzyme-based
biofuel cell (BFC). In this hybridized design, we used piezo-
electric poly(vinylidene fl uoride) (PVDF) nanofi bers (NFs) as
the working component for mechanical energy harvesting. The
working principle of the PVDF NG is based on the piezoelectric
properties of the PVDF NF. As the device is deformed under
alternating compressive and tensile force, the NFs drive a fl ow
of electrons back and forth through the external circuit. 17 The
enzymatic BFC was used to convert the chemical energy of glu-
cose and oxygen in the biofl uid into electricity. The electrodes
were patterned onto a Kapton fi lm and coated with multiwalled
carbon nanotubes, and fi nally immobilized glucose oxidase
(GOx) and laccase form the anode and cathode, respectively,
for the BFC. A HC structure can be fabricated on a single PVDF
NF for energy harvesting. 39
Nanogenerators as active sensors A nanogenerator can also function as an active sensor by using
its electric output as the signal to be detected. Based on such
an idea, we recently demonstrated a self-powered sensor for
detecting low frequency vibrations. 40 Furthermore, we fabri-
cated a self-powered pressure sensor based on the BFC and
NG on a single fi ber,41 as shown in Figure 8 a. ZnO NW fi lms
grown around a carbon fi ber forms a textured fi lm with the
c -axis radially pointing outward. Mechanical straining would
generate a piezopotential across the thickness of the NW fi lm
( Figure 8b ). Thus, the output of the NG is sensitive to the
pressure change. This experiment demonstrates that not only
can we use the HC or NG as an energy harvester, but also as
an active sensor for detecting a mechanical signal from the
environment.
Piezotronics In order to illustrate the basic concept of piezotronics, we fi rst
start from a traditional metal oxide semiconductor fi eld-effect
transistor (MOSFET). For an n-channel MOSFET ( Figure 9a),
the two n-type doped regions are the drain and source; a thin
insulator oxide layer is deposited on the p -type region to serve
as the gate oxide, on which a metal contact is made as the
gate. The current fl owing from the drain to the source under an
applied external voltage VDSVV is controlled by the gate voltage VGVV ,
which controls the channel width for transporting the charge
carriers. A piezotronic transistor is a metal-NW-metal structure,
as schematically shown in Figure 9b once a strain is applied
through the substrate. 41 The fundamental principle of the piezo-
tronic transistor is to control the carrier transport at the metal-
semiconductor interface through tuning at the local contact by
creating a piezopotential at the interface region in the semicon-
ductor by applying a strain. This structure is different from the
complementary metal oxide semiconductor (CMOS) design.
First, the externally applied gate voltage is replaced by an inner
crystal potential generated by the piezoelectric effect, thus, the
“gate” electrode is eliminated. This means that the piezotronic
transistor only has two leads: drain and source. Second, control
over channel width is replaced by control at the interface. Since
Figure 7. Design of a compact hybrid cell (HC) structure
consisting of a dye sensitized solar cell (DSSC) and a
nanogenerator (NG). (a) Schematic illustration of the HC,
illuminated by sunlight from the top and excited by ultrasonic
waves from the bottom. The ITO layer on the DSSC and the
GaN substrate are defi ned as the HC cathode and anode,
respectively; Spiro-MeoTaD is a polymer. (b) A comparison of
power output J–V characteristics of a HC. The top left inset is theVI–V characteristic of the NG when the solar cell is off. The bottomVright inset is a replot of the displayed curves at short circuit. 37
FROM NANOGENERATORS TO PIEZOTRONICS—A DECADE-LONG STUDY OF ZNO NANOSTRUCTURES
Piezo -phototronic effec t in a photodetector The basic principle of a photon detector is
based on the photoelectric effect, in which the
Figure 11. Piezotronic transistor. (a) Schematic of an Ag-ZnO-Ag strain gated
transistor on a fl exible substrate. The deformation in the transistor is indicated through
a change in shape of the substrate. (b) Changes in transport characteristics of a
Ag/ZnO-nanowire/Ag device from symmetric I–V characteristics (black) to asymmetricVrectifying behavior when stretching (red) and compressing (green) the wire. Inset:
equivalent circuit models of the device in corresponding to the observed I–V curves, Vdifferent sizes of diode symbols are used to illustrate the asymmetric Schottky
contacts at the two ends of the nanowire. (c–e) Band diagrams for illustrating the
piezotronic effect on local contact of the device without and with the presence of
piezopotential. The sign of the piezopotential is indicated in the nanowire. 49
Figure 12. Enhancing photon detection sensitivity by the piezo-phototronic effect.
(a) Schematic band diagrams for illustrating the effect of local piezo-charges on the
Schottky contact showing the piezotronic effect on separating the photon induced
charges. (b) Response of a ZnO wire UV detector (in units of A/W) as a function of strain
under different excitation light intensity on a natural logarithmic scale. 55
FROM NANOGENERATORS TO PIEZOTRONICS—A DECADE-LONG STUDY OF ZNO NANOSTRUCTURES
823MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
e-h pairs generated by a photon are separated
by either a p-n junction or a Schottky bar-
rier ( Figure 12a ). If the Schottky barrier is too
high, the holes will be trapped at the semicon-
ductor side so that they cannot be effectively
annihilated by the free electrons in the metal
( Figure 12a ), thus reducing the photocurrent.
If the Schottky barrier is too low, the photon-
generated electrons cannot be effectively driven
away from the interface region, so they can be
easily recombined with the holes, which also
results in low photocurrent. An optimization of
SBH can give the maximum photocurrent. Such
a result was observed in a simple photocell.52
By tuning the SBH in a ZnO wire-based
UV sensor through applying a strain, we can
improve the sensitivity of the UV detector,
even when the illumination intensity is rather
weak.53 The response of the photodetector is
enhanced by 530%, 190%, 9%, and 15% upon
4.1 pW, 120.0 pW, 4.1 nW, and 180.4 nW UV
light illumination, respectively, onto the wire by
introducing a –0.36% compressive strain in the
wire ( Figure 12b ); this effectively tunes the SBH at the contact
by the local piezopotential produced. The sensitivity for weak
light illumination is especially enhanced by introducing strain,
although the strain has little effect on the sensitivity to stronger
light illumination. Our results show that the piezo-phototronic
effect can enhance the detection sensitivity more than fi vefold
Figure 14. Piezo-phototronic in a GaN/ZnO LED. Enhancement of emission light intensity and conversion effi ciency of a ( n( ( -ZnO wire)-
( p( ( -GaN fi lm) LED under applied strain. (a) CCD images recorded from the emitting end of a packaged single wire LED under different
applied strains. (b) Integrated emission light intensities from the data shown in (a), showing a huge increase in the emission intensity with
the increase of the applied compressive strain. The inset is the injection current of the LED at 9 V bias voltage with increase in strain. (c)
Schematic energy band diagram of the p-n junction without (upper) and with (lower, red line) applied compressive strain, where the channel
created at the interface inside ZnO is due to the piezopotential created by strain. The slope of the red line in the lower image at the ZnO
side represents the driving effect of the piezopotential on the movement of the charge carriers.50
Figure 13. Piezo-phototronic effect in a solar cell. (a) Schematic of a fabricated [0001] type
device and top-down optical image of a device. (b) Dependence of short-circuit current Isc
and the open-circuit voltage VocVV on applied strain. (c) The piezopotential distributions in the
stretched device of [0001] type, and the corresponding (d) band diagram of P3HT/ZnO with
the presence of negative piezoelectric charges. The blue line indicates the energy band
diagram modifi ed by the piezoelectric potential in ZnO.55
FROM NANOGENERATORS TO PIEZOTRONICS—A DECADE-LONG STUDY OF ZNO NANOSTRUCTURES
THE WORLD’S RESOURCE FORVARIABLE TEMPERATURESOLID STATE CHARACTERIZATION
TTTAAWWMMEERR
HALL EFFECT MEASUREMENT SYSTEMS
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54. Y. Liu, Q. Yang, Y. Zhang , Z.Y. Yang , Z.L. Wang, Adv. Mater., in press ( 2012).55. Y. Yang, W.X. Guo, Y. Zhang , Y. Ding , X. Wang, Z.L. Wang , Nano Lett.o 11,4812 ( 2011 ).56. Y. Liu , Q. Yang , Y. Zhang, Z.Y. Yang, Z.L. Wang , Adv. Mater. 24, 1410 ( 2012 ).57. Y. Zhang , Z.L. Wang, Adv. Mater., in press (2012).58. Y. Zhang , Y. Yang , Z.L. Wang, Energy Environ.y Sci. 5, 6850 ( 2012 ).59. http://en/ .wikipedia. org /wiki/ / Mechanosensation/ .60. D. Choi , M.J. Jin, K.Y. Lee , S.-G. Ihn, S. Yun , X. Bulliard, W. Choi, S.Y. Lee ,S.-W. Kim, J.-Y. Choi, J.M. Kim, Z.L. Wang , Energy Environ.y Sci. 4, 4607 ( 2011 ).61. X.Y. Xue , S.H. Wang , W.X. Guo , Y. Zhang, Z.L. Wang , Nano Lett.o ; doi: 10.1021/n13028791 ( 2012 ).
Zhong Lin Wang is the Hightower Chair inmaterials science and engineering, a Regents’Professor, and an Engineering DistinguishedProfessor and director of the Center forNanostructure Characterization at the GeorgiaInstitute of Technology. He received his PhDdegree from Arizona State University iny 1987. Hewas elected as a foreign member ofr thef ChineseAcademy ofy Sciencesf in 2009; a member ofr thefEuropean Academy ofy Sciencesf in 2002; andFellow ofw thef American Physical Society iny 2005,of AAAS in 2006, of the Materials ResearchSociety iny 2008, of thef Microscopy Societyy ofyAmerica in 2010, and of thef World Innovation
Foundation in 2002. He received the 2012 Edward Orton Memorial Lecture Awardfrom the American Ceramic Society, the 2011 MRS Medal from the MaterialsResearch Society, the 1999 Burton Medal from the Microscopy Societyy ofy America,fthe 2001 S.T. Li prize for Outstanding Contribution in Nanoscience andNanotechnology, the 2009 Purdy Awardy from the American Ceramic Society, and theNanoTech Briefs Top 50 award in 2005. Wang has authored and co-authored fivefiscientificfi reference books and textbooks and more than 730 peer-reviewedjournal articles, 50 review papers, and book chapters. He also holds 32 patents.Wang can be reached by email at [email protected].
delivered throughout the tumor. We can examine individual cells
and again show individual particles circulating from the point
where the animal is dosed to the inside of the cancer cell. We
started treating patients with these nanoparticles in the spring
of 2008, and in 2010, we published the fi rst results showing that
this technology can actually be used in a living human being. 14
Figure 8 illustrates what we believe happens when we
infuse these nanoparticles into the patient: (step 3) they circu-
late, (step 4) enter the tumor, and (step 5) move into the tumor
cells. These nanoparticles contain chemical sensors that can
recognize that they have entered the vesicles, and we have
built in a mechanism to (step 6) bring them out of the vesicles
and release the RNA that then will be (step 7) taken up by the
protein machinery, guide it to the mRNA, and (step 8) cut the
mRNA to (step 9) stop the production of protein. 5 In principle,
if this mechanism was acting in the way we believe it is
acting, we should see a decrease in the mRNA, a decrease in
the protein, and a new fragment of RNA. We were fortunate
to obtain biopsies from patients at three different dose levels:
18, 24, and 30 mg-siRNA/m2. When we examined the tissues,
we saw that for the lowest dose, using the Au-PEG-AD stain,
we saw no nanoparticles. When we examined the intermediate
dose, we started to see some nanoparticles, and then at the
higher dose, we saw many nanoparticles. After a month,
we examined biopsies of one of the patients where we saw
the nanoparticles, and we observed that the nanoparticles had
all disassembled (the disassembled components are suffi ciently
small to escape the body via the kidney). After a repeat dose,
we saw the nanoparticles returning again, in a very reproducible
manner. Thus, for the fi rst time, we have seen a dose-dependent
accumulation of these nanoparticles within tumor cells from a
systemic administration: this is the fi rst example of this using
nanoparticles of any type.
A very encouraging result was to fi nd that we did not see
any nanoparticles in the tissue adjacent to the tumor. We believe
that this is good evidence to suggest that these nanoparticles
accumulate in tumors through the leaky vessels, but cannot
accumulate in the healthy tissue next to the tumor.
When we examined the tissue through staining, we
observed reductions in the protein we were trying to inhibit.
When we looked for either the protein or the level of the
mRNA, we found it is reduced. Additionally, we showed the
presence of RNA fragments after dosing, and by sequencing
these fragments, we revealed that the mRNA was cut at exactly
the right position by the RNAi mechanism. This was the fi rst
example showing that we could perform RNAi in a patient.
Thus, we have demonstrated that RNAi can be successful
in a human patient and gives a high quality of life during
treatment.
The future We are now learning a great deal about design rules and how
to control the properties of these nanoparticles to make them
more biocompatible and more effective. The newer particles
I have just shown have ever-increasing functionality in order
to perform the required function at the right place and at the
right time. There is no doubt that
these nanoparticles will be com-
plex, but hopefully, this will be
worth the effort. We can now
focus on ways to create very
effective therapeutics for solid
tumors and give patients a high
quality of life.
One thing I am very proud
of is that we have been able to
stop the production of an indi-
vidual gene in the tumor of the
patient, thus there is no reason
we cannot stop the production
of multiple genes at the same
time. We could take a biopsy
from a patient, fi nd which genes
are causing their disease, create
RNAs to treat the patient, and be
able to follow how the treatment
of the disease is progressing,
maybe by simply taking a prick
of blood. In the future, one could
envision that there will be an app
on a smartphone that will read
the information from a prick of
blood, call up a physician, and
Figure 8. Schematic of the delivery and function of treating a patient with targeted nanoparticles
containing RNA.
FIGHTING CANCER WITH NANOPARTICLE MEDICINES ― THE NANOSCALE MATTERS
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report the results. This will enable the physician to know how
the disease is either regressingr or progressing,r and this infor-
mation couldn bed used dynamicallyd toy decide the next dose,t what
genes it should attack, and when it should be administered to
the patient. This is really a dream, but the basic science and
engineering for every step of thisf process has already been
worked out. It has yet to be integrated, but the basic principles
of suchf a system are all in place, and every step of thef way
required newd nanoscience and nanoscaled engineering. My hope
is that at least some fraction of thisf will be achieved in the
near future.r
In conclusion, I hope I have been able to convincingly show
very high potential for ther use of nanoparticlesf to create new
types of therapiesf for treatmentr oft solidf tumorsd that providet
patients with a high quality of life.f It ist very encouraging for
me to see patients in these early clinical trials having a high
quality of lifef when treated withd these therapies.
I have had thed great privileget of workingf with wonderful
people everywhere—at Caltech,t and withd various companies.
I would very much like to thank all the patients who have
been treated in these trials. It has been a pleasure for mer to
be present int the treatment roomst with them in a number ofr
different trials.t Finally, I would onced again like to thank thek
Kavli Foundation, and MRS,d for givingr me the opportunity to
speak withk you tonight.
References1. A. Jemal , R. Siegel, J. Xu, E. Ward , CA-Cancer J.r Clin. 60, 277 (2010). 2. Data from the World Bank, www.w worldbank . org .3. T. O’Callaghan , Nature 471 ( 7339 ), S2 ( 2011 ).4. M.R. Dreher,r W. Liu , C.R. Michelich, M.W. Dewhirst, F. Yuan, A. Chilkoti,J. Natl. Cancer Inst.r 98 ( 5 ), 335 ( 2006 ).5. M.E. Davis , Mol. Pharmacol. 6 ( 3 ), 659 ( 2009 ).6. L. Lacenda, M.A. Herrero, K. Venner ,r A. Bianco , M. Prato, K. Kostarelos, Small4 ( 8 ), 1130 ( 2008 ).7. A. Ruggiero, C.H. Villa , E. Bander,r D.A. Rey,y M. Bergkvist, C.A. Batt,K. Manova-Todorova, W.M. Deen, D.A. Scheinberg, M.R. McDevitt, PNAS 107( 27 ), 12369 ( 2010 ).8. J.A.J. Fitzpatrick, S.K. Andreko , L.A. Ernst, A.S. Waggoner,r B. Ballou,M.P. Bruchez , Nano. Lett. 9 (7 ), 2736 ( 2009 ).9. H. Cabral , Y. Matsumoto , K. Mizuno, Q. Chen , M. Murakami, M. Kimura ,Y. Terada , M.R. Kano, K. Miyazono , M. Uesaka, N. Nishiyama, K. Kataoka, Nat.Nanotechnol. 6 , 815 (2011).
10. S.R. Popielarski, S. Hu-Lieskovan, S.W. French , T.J. Triche, M.E. Davis,Bioconjugate Chem.e 16 ( 5 ), 1071 ( 2005 ).11. W. Jiang, B.Y.S. Kim , J.T. Rutka , W.C.W. Chan, Nat. Nanotechnol. 3 (3), 145( 2008).12. S. Mishra , P. Webster ,r M.E. Davis , Eur. J. Cell Biol.l 83, 1 ( 2004 ).13. A.Z. Fire , “Gene silencing by doubley stranded RNA” (Nobel Lecture, December 8,r2006), p. 224 ; www.w nobelprize.org / nobel_prizes/ / medicine/ / laureates/ /2006/ /fi// re_filecture . pdf .14. M.E. Davis , J.E. Zuckerman, C.H.J. Choi, D. Seligson , A. Tolcher,r C.A. Alabi,Y. Yen , J.D. Heidel , A. Ribas, Nature 464 , 1067 (2010).
Mark E. Davis is the Warren and KatharineSchlinger Professor of Chemical Engineeringat the California Institute of Technology anda member of the Experimental TherapeuticsProgram of thef Comprehensive Cancer Centerr atrthe City of Hope. His research efforts involvematerials synthesis in two general areas: namely,zeolites and other solids that can be used formolecular recognitionr and catalysis and polymersfor ther delivery ofy af broad range of therapeutics.fHe is the founder ofr Insertf Therapeutics Inc. andCalando Pharmaceuticals Inc. He also has beena member of the scientificfi advisory boards ofSymyx and Alnylam. Davis has more than 375
scientificfi publications, 2 textbooks, and more than 50 patents. He is a foundingeditor ofr CaTTech andh has been an associate editor ofr Chemistry ofy Materialsf ands theAIChE Journal.E He also is the recipient of thef Colburn and Professional ProgressAwards from the American Institute of Chemicalf Engineers (AIChE), the Ipatieff,Langmuir, Murphree, and Gaden Prizes from the American Chemical Society (ACS),yand the National Science Foundation (NSF) Alan T. Waterman Award. He waselected to the National Academy ofy Engineeringf in 1997, the National Academy ofySciences in 2006, and the Institute of Medicine of the National Academies in2011. Davis can be reached by email at [email protected] .
Photodeprotection chemistries generally describe the ability
to cleave a portion of a molecule in a selective manner using
light. Photodeprotection can serve as an effi cient method to
selectively alter the compositions of side chains in polymeric
materials. Functional groups containing pendant 2-nitrobenzyl
groups via ester linkages can be cleaved to produce the
nascently deprotected carboxylic acid and the newly formed
2-nitrobenzaldehyde by-product. Variations on this chemistry
have also been used for three-dimensional patterning of recog-
nition molecules in hydrogels via single- or two-photon pattern-
ing of static networks.109,110 This synthetic strategy can also be
used to create dynamic hydrogel biomaterial networks. Anseth
et al. demonstrated the formation of photolyti-
cally cleavable cell-seeded hydrogel networks
based on poly(ethylene glycol) (PEG) func-
tionalized with 2-nitrobenzyl groups. 111 Briefl y,
linear PEG precursors are functionalized with
acrylate-containing 2-nitrobenzyl groups via
ester linkages. These photolabile PEG pre-
cursors form cross-linked hydrogel networks.
The storage modulus of the networks, which is
directly proportional to the cross-link density,
can be reduced irreversibly by over 90% after
exposure to benign UV irradiation of λ = 365 nm
at 10 mW/cm 2 for 10 minutes. Therefore, the
mechanical properties of the network can be
dynamically tuned in space and time through
controlled irradiation. A parallel synthetic
approach can be used to create networks in
which cell adhesion domains can be selectively
removed using photolysis. Human mesenchy-
mal stem cells cultured in PEG hydrogels with
photocleavable cell-binding domains engage
in accelerated chrondrogenesis upon selective
removal of this integrin binding motif. Similar
chemistries can be utilized for real time control
of elasticity in hydrogel substrates as well. 112,113
Practical aspects of these techniques are sum-
marized in Figure 5 . Figure 5a is a schematic
of the formation of a photodegradable polymer
network through free radical photopolymer-
ization. The green groups represent dienes
that can undergo free radical polymerization
to create the cross-linked network. The blue
groups represent photodegradable segments
that can be cleaved to selectively remove parts
of a network. One strategy for selective photo-
cleavage of cross-linked networks uses masking
combined with single-photon excitation to create
two-dimensional structures in a manner that is
similar to photolithography ( Figure 5b ). Another strategy uses
two-photon absorption in which laser scanning microscopy can
be used to create arbitrary three-dimensional features by selective
photocleavage ( Figure 5c ).
Light-activated hydrogel networks are advantageous because
direct manipulation of cell-biomaterial interactions is achiev-
able, although irreversible. Nonetheless, there is a broad set
of biological questions that can be answered using material
systems that are able to administer step changes in biomaterial
response. The emerging challenge is to design materials, sys-
tems, and experiments that are able to eventually provide insight
into disease progression such that complementary treatments
may eventually be discovered.
Conclusions and outlook The continued interest in dynamic cell-biomaterials interac-
tions using smart materials will lead to discoveries that could
Figure 5. Methods for photodegradable hydrogel synthesis and patterning.
(a) Photodegradable hydrogels formed by redox-initiated, free-radical chain polymerization,
which is indicated by R*. The resultant network is comprised of polyacrylate kinetic chains*(green) connected by PEG-based cross-links (black) with photocleavable moieties (blue) in
the backbone. (b) Using a chrome mask, the surface of the photocleavable hydrogel can
be patterned with features of depths that depend upon exposure time. Features can be
generated within minutes of irradiation time. (c) Use of a laser-scanning microscope (LSM)
with a 405 nm laser can also be used to create three-dimensional patterns by precisely
moving the laser in the x–y plane using a scanner. The z-dimension is controlled with ayhigher minimum feature resolution by either controlling the focal plane of the laser or
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Stephen Kustra received his master of sciencedegree in biomedical engineering at CarnegieMellon University and his bachelor of sciencedegree in biomedical engineering from theUniversity of Connecticut. His current researchinterests include biomaterials-based medicaldevices and smart interfaces for understandingfundamentals of cell-biomaterials interactions.Kustra can be reached by email at [email protected].
Christopher J. Bettinger isr an assistant professorat Carnegie Mellon University (CMU) in theDepartments of Materialsf Science and BiomedicalEngineering. He directs the laboratory forBiomaterials-Based Microsystems and Electronicsat CMU, which is broadly interestedy in the designof novel materials and interfaces that promotethe integration of medical devices with thehuman body. Bettinger has received manyhonors, is a co-inventor on several patents, andwasafi nalistfi in theMIT $100KEntrepreneurshipCompetition. Bettinger received an SB degree inchemical engineering, an M.Eng. degree inbiomedical engineering, and a PhD degree in
materials science and engineering as a Charles Stark Draper Fellow, all from theMassachusetts Institute of Technology. He completed his post-doctoralfellowship at Stanford University in the Department of Chemical Engineering asan NIH Ruth Kirschstein Fellow. Bettinger can be reached by email at [email protected].
Frontiers in Thin-Film Epitaxy and Nanostructured Materials JMR Special Focus Issue, July 2013
www.mrs.org/jmr-focus
CALL FOR PAPERSSubmission Deadline November 15, 2012
on a hinge material, such as Au or ar polymer, and liquefiedfi
by heating, causing it to deform to reduce surface energy;
this deformation generated the torque required to rotate the
fl ap.fl Building on the body of literaturef on electromechanical
actuation,26 Smela et al. showed electrochemically controlled
bending and foldingd of microstructures,f such as spirals or cubicr
boxes using bilayer strips or hinges of Auf and polypyrrole
(PPy, doped with sodium dodecyl benzene sulfonate).27,28 In
this case, the Au/PPy strips curved when the PPy thin filmfi
was electrochemically oxidized, causing it to shrink. In addi-
tion, a number ofr activef and passive mechanisms have been
explored, including the use of electrical,f magnetic, electro-
chemical, optical, pneumatic, thermal, and chemical stimuli
to manipulate the stresses in single or multilayerr fir lmsfi so that
they cany ben curved ord foldedr onlyd wheny desired.n 24 Some of thesef
stimuli require that the structures are tethered to substrates,
Self-folding thin-fi lm materials: From nanopolyhedra to graphene origami Vivek B.k Shenoy and David H. Gracias
Self-folding of thinf filmsfi is a more deterministic form of self-assemblyf wherein structures
curve or fold up either spontaneously on release from the substrate or in response to specificfi
stimuli. From an intellectual standpoint, the study of thef self-folding of thinf filmsfi at small size
scales is motivated by the observation that a large number of naturallyf occurring materials
such as leaves and tissues show curved, wrinkled, or folded micro- and nanoscale geometries.
From a technological standpoint, such a self-assembly methodology is important since it
can be used to transform the precision of existing planar patterning methods, such as
electron-beam lithography, to the third dimension. Also, the self-folding of graphenef promises
a means to create a variety of three-dimensionalf carbon-based micro- and nanostructures.
Finally, stimuli responsive self-folding can be used to realize chemomechanical and tether-
free actuation at small size scales. Here, we review theoretical and experimental aspects of
the self-folding of metallic,f semiconducting, and polymeric fi lms.fi
Vivek B. Shenoy, Engineering Department, Brown University; [email protected] David H. Gracias, Departments of Chemical and Biomolecular Engineering , Chemistry and the Institute for Nanobiotechnology,y The Johns Hopkins University ; [email protected] DOI: 10.1557/mrs.2012.184
SELF-FOLDING THIN-FILM MATERIALS: FROM NANOPOLYHEDRA TO GRAPHENE ORIGAMI
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Vivek B. Shenoy is a professor of engineeringat Brown University. He received his doctoratedegree from the Ohio State University,performed postdoctoral research at Brown,and was a visiting Fellow at the University ofCambridge prior to starting his independentresearch group in 2000. He has published over100 journal articles in the areas of computationalfmaterials science and mechanics.
David H. Gracias is an associate professor atthe Johns Hopkins University. He received hisPhD degree from UC Berkeley, performedpostdoctoral research at Harvard, and workedat Intel Corporation prior to starting hisindependent research group in 2003. He haspublished 80 journal articles and is a co-inventorof 20 patents in the areas of micro- andnanotechnology, self-assembly, and interfacialscience.
EXTREMES OF HEAT CONDUCTION ― PUSHING THE BOUNDARIES OF THE THERMAL CONDUCTIVITY OF MATERIALS
863MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
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David G. Cahill has been a faculty member atthe University of Illinois at Urbana-Champaign(UIUC) since 1991. He earned his PhD degreein condensed matter physics from CornellUniversity in 1989 and then worked as apostdoctoral research associate at the IBMWatson Research Center. In 2005, he wasnamed Willett Professor of Engineering at UIUCand was appointed head of the Department ofMaterials Science and Engineering in 2010. Hisresearch program focuses on developing amicroscopic understanding of thermal transportat the nanoscale; the development of newmethods of materials processing and analysis
using ultrafast optical techniques; and advancing fundamental understanding ofinterfaces between materials and water. Cahill received the Peter Mark MemorialAward from the American Vacuum Society (AVS); is a fellow of the AVS, theAmerican Physical Society (APS), and the Materials Research Society; and ischair-elect of the Division of Materials Physics of the APS. Cahill can be reachedby email at [email protected].
For more information please visit www.mrs.org/mrc or email [email protected].
MRS seeks awardnominations for 2013Deadline: October 1, 2012
Mid-Career Researcher Awardwww.mrs.org/mraThe Materials Research Society is nowaccepting nominations for the Mid-Career Researcherr Awardr tod be presentedat thet 2013 MRS Spring Meeting in SanFrancisco, Calif.
The annual award recognizes ex-ceptional achievements in materials re-search made by mid-career profession-rals. It ist intended tod honor anr individual
who is between the ages of 40fand 52d at thet time of nomina-f
tion. Exceptions may be made for aninterruption in career progression dueto family or militaryr service. The awardrecipient mustt alsot demonstrate notableleadership in the materials area.
The award consistsd of af $5,000 cashprize, a presentation trophy, and ad cer-tifi cate.fi Meeting registration fee, trans-portation, and hoteld expenses to attendthe Materials Research Society SpringMeeting at whicht the award isd presentedwill be reimbursed.
The Mid-Career Researcher Awardis made possible through an endow-ment established by Aldrich MaterialsScience.
Outstanding Young Investigator Award www.mrs.org/oyiThe Materials Research Society is ac-cepting nominations for ther Outstanding
Young Investigator (OYI)r Award tod bepresented atd thet 2013 MRS Spring Meet-ing in San Francisco.
The OYI Award recognizesd outstand-ing interdisciplinary scientifi cfi work inkmaterials research by a scientist ort en-rgineer underr ther age of 36f (as of Janu-fary 1, 2013). The award recipientd musttshow exceptional promise as a develop-ing leader inr the materials area.
The award consistsd of af $5,000a prize,a presentation trophy, and ad citation cer-tificate.fi Reasonable travel expenses toattend the MRS Meeting at which theaward isd presented andd thed meeting reg-istration fee will be reimbursed.
Innovation in MaterialsCharacterization Awardwww.mrs.org/IMCAThe Materials Research Society is ac-cepting nominations for ther Innovationin Materials Characterization Award todbe presented at the 2013 MRS SpringMeeting in San Francisco, where the re-cipient ist invited tod speak atk thet AwardsCeremony.
The award recognizesd an outstandingadvance in materialsn characterization thatnnotably increases the knowledge of thefstructure, composition, in situ behaviorunder outsider stimulus, electronic, me-chanical, or chemicalr behavior, or otherrcharacterization featuren of materials.f It istnot limitedt tod the method ofd characteriza-f
tion or ther class of materialf observed.The annual award consists of af
$5,000 cash prize, a presentationa trophy,and a certifi cate.fi Meeting registrationfee, transportation, and hotel expensesto attend thed MRS Meeting at whicht theaward isd presented willd be reimbursed.
The Innovation in Materials Charac-terization Award hasd been endowed bydToh-Ming Lu and Gwo-Chingd Wang.
Materials ResearchSociety Fellowswww.mrs.org/fellowsThe Materials Research Society seeks torecognize as “MRS Fellow” outstandingmembers who are notable for theirr sus-rtained andd distinguishedd contributionsd tothe advancement oft materialsf research.It ist intended that—representingd excel-lence in science and engineering, anddedication to the advancement of ma-fterials research—the MRS Fellows willcollectively exemplify the highest idealstof accomplishmentf andt serviced embod-ied ind the MRS Mission.
Nomination is open to any MRSmember in good standing, whosemembership has been continuous forat least fivefi years preceding receipt ofthe nomination. MRS Fellow is a life-time appointment.
The deadline for submission of allfnominations is October 1, 2012. Forguidelines and applicationd forms, accessthe MRS website at www.mrs.org/awards or contactr Lorrit Smiley, MaterialsResearch Society, 506 Keystone Drive,Warrendale, PA 15086-7573,A USA;email [email protected].
Registration opens mid-September November 25 – 30, 2012 www.mrs.org/fall2012
865MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
The fundamental basis of materialsfscience is in understanding the re-
lationship between the microstructure ofmaterials and theird macroscopicr proper-ties. Unlike traditional materials, whichare usually treated asd homogeneous andisotropic, fiber-reinforcedfi compositescan be highly anisotropic depending onthe localized orientation of fi bers.fi Forfi berfi composites, researchers are veryheavy-handed with the microstructurein that they can control the internalstructure during the composites manu-facturing process through inducing fi berfiorientation duringn lay-up or bendingr andtwisting the fi bersfi using textile tech-niques. The book Composite reinforce-ments for optimumr performance is aimedat addressing this interrelationship be-tween the composite microstructure andthe resulting properties and performance.d
The book isk structured intod four pri-rmary sections: materials for reinforce-rments in composites; structures forreinforcements in composites; proper-ties of compositef reinforcements; and
characterizing and modelingd reinforce-ments in composites. The fi rstfi sectionhighlights the common fiberfi reinforce-rments and their properties,r along witha section addressing carbon nanotubesas an emerging reinforcement. The in-formation contained in this section isfundamental to most textbookst on fiber-fireinforced compositesd and isd presentedin a clear andr straightforwardd way.d
The second sectiond focuses primarilyon textile preform structures for com-posites, addressing woven and braideddstructures in both two-dimensional andthree-dimensional confi gurationsfi andmodeling their geometric properties.This section is comprehensive in thatit coverst the textile forming technologyand thed resulting fabric architectures andcomposite properties.
The third sectiond addresses the prop-erties of thef textiles and compositesd andhighlights both experimentalh and model-ding efforts. The finalfi section examinesthe characterization of andf modelingd ofcomposites. It alsot includes chapters on
modeling the mechanical properties atvarying scales and modelingd of differentfmanufacturing processes, such as of res-fin transfer molding,r injection molding,and fabricd draping/forming processes.
As with many books where multipleauthors contribute individual chapters,there often is some overlap. However,Composite reinforcements for optimumrperformance covers appropriate breadthand depth on a wide variety of topicsfthat aret not oftent found withind a singlereference. The treatment oft textilef com-posites, from a manufacturing, model-ing, and characterization viewpoint isparticularly strong. Two chapters in thebook addressk discontinuous fi berfi com-rposites composed ofd eitherf carbonr nano-tubes or shortr fi bers.fi Both chapters dealprimarily with processing in terms ofexamining fl ow-inducedfl orientation.d Thebook, while already rather long,r wouldbenefitfi fromt a chapter onr the mechanicsof discontinuousf fibersfi and composites.d
At thet University ofy Delaware,f I teachan advanced undergraduated and gradu-date-level course on composite materials,and Id think thatk thist book isk an excellentreference for both scientists and engi-neers working with, or studying, fi berficomposites. I plan to keep this book onkreserve at thet library as a reference forthe course.
Reviewer: Erik Thostensonk of thef De-partment oft Mechanicalf Engineeringland Centerd forr Compositer Materials atthe University of Delaware.f
Sandia National Laboratories is one of thef country’s largest research facilities employing nearly 8,500 people at
major facilities in Albuquerque, New Mexico and Livermore, California. Please visit our website at www.sandia.gov.
We are seeking applicants for the President Harry S. Truman Fellowship in National Security Science and
Engineering. Candidates for this position are expected to solve a major scientific or engineering problem in their
thesis work or have provided a new approach or insight to a major problem, as evidenced by a recognized impact in
their field.
Sandia’s research focus areas are: bioscience, computing and information science, engineering science, materials
science, nanodevices and microsystems, radiation effects and high energy density science, and geoscience.
Candidates must meet the following requirements: U.S. citizenship, the ability to obtain and maintain a DOE “Q”
clearance, and a Ph.D. (3.5 undergraduate and 3.7 graduate GPA preferred), awarded within the past three years at
the time of application,f or completed Ph.D. requirements by commencement of appointment.f Candidates must be
seeking their first national laboratory appointment (pre postdoc internships included).
The Truman Fellowship is a three-year appointment normally beginning on October 1. The salary is $110,900 plus
benefits and additional funding for the chosen proposal. The deadline to apply is November 1st of eachf year.
For complete application instructions, please visit: http://www.sandia.gov/careers/students_postdocs/fellowships/
truman_fellowship.html
Please submit the complete package to: Yolanda Moreno, Sandia National Laboratories, P.O Box 5800, MS0359,
Albuquerque, NM 87185-0359, or email [email protected]. Please reference Job ID: 640971. All materials must
be received by November 1, 2012.
U.S. Citizenship Required.
Equal Opportunity Employer. M/F/D/V.
Harry S. Truman Fellowshipin National Security Science and Engineering
Operated byd
ASSISTANT PROFESSORMATERIALS CHEMISTRY
The Department of Chemistryf at the University atBuffalo (UB), State University of Newf York invitesapplications for ar tenure-track faculty position inexperimental materials chemistry at the AssistantProfessor level.r All areas of materialsf chemistrywill be considered; candidates with interests inimaging, microscopy, or spectroscopy areparticularly encouraged to apply. The successfulcandidate will contribute, through research andteaching, to a new interdisciplinary graduateprogram in Materials Science and Engineering atUB. An assistant professor isr expected to develop
867MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
CAREER CENTRAL
As part oft af major initiative,r the Institute of ChemicalfSciences and Engineering (ISIC) at EPFLt invites appli-cations for severalr faculty appointments in Chemical En-gineering. Exceptional applicants with expertise in en-ergy-related topics, including solar energyr conversion,chemical, electrochemical and biochemical energy con-version, carbon capture and utilization, are especiallyencouraged to apply. Appointments at thet Assistant Pro-tfessor level (tenure track) are envisioned, but seniorfaculty levels (Associate/Full) may also be considered.
A PhD in Chemical Engineering or ar related field and anexcellent trackt record of innovativef research and leader-ship are generally required. The successful candidatewill be expected to establish and direct at vigorous, inde-pendent research program and be committed to excel-lence in teaching at botht the undergraduate and graduatelevels.
Applications including cover letter,r curriculum, vitae,m publi-,cations list, concise, statements of researchf andh teachingd in-terests as well as the names and addressesd (including email)of fivef references should bed submitted ind electronicn formatvia thea website http://sbpositions.epfl.ch/applications/by October 15, 2012.,
The EPFL is consistently evaluated asd one of thef leadinguniversities in sciencen and engineeringd in Europe.n We offerinternationally competitive salaries, start-up resourcesand benefits.d The EPFL aims for ar stronga presence ofwomen amongst itst faculty, and, qualifiedd femaled candi-dates are strongly encouraged tod apply. More informationabout EPFLt and thed Institute of Chemicalf Sciences andEngineering can be found at:d http://www.epfl.ch/ andhttp://isic.epfl.ch. For additionalr information about thistcall for applications, please contact the director of thefinstitute, Prof., Paul Dyson ([email protected]).
Faculty Positions in Chemical Engineeringat the Ecole polytechnique fédérale de Lausanne (EPFL)
Located ind northern New Mexico,w Los, Alamos National Laboratoryl isya multidisciplinary researchy institution engaged ind strategic sciencec onbehalf off nationalf security.l Our. Centerr forr Integratedr Nanotechnologiesdhas the following opening:g
CHEMISTRY POSTDOCFocus on interfacial & colloidal chemistry and photophysicsof carbonf nanomaterials. Colloidal. & interfacial chemistrybackground required to support DOE program generatingsolution-based carbon nanomaterials for photovoltaicrapplications. Requires. experimental background/strongpublication record in colloidal chemistry or nanomaterialrcharacterization and PhD in Chem, Materials, Science, Physics,,or relatedr within past 5 years or soonr to be completed.
Director’s Fellowship or Marier Curie, Richard, P. Feynman,P. J.,Robert Oppenheimer, or, Frederickr Reinesk Fellowships possible.
Apply online at http://bit.ly/CINTPostdoc2 or visitrhttp://careers.lanl.gov and reference vacancy IRC9229.
AA/EOE
MINDS THAT MATTER
Material Sciences Division Director
Lawrence Berkeley National Laboratory (LBNL) is seeking a dynamicscientific leader to serve as the Division Director of thef Materials SciencesDivision (MSD). MSD is a research division of aboutf 700 staff andf guests,involving scientists at LBNL and faculty and students at UC Berkeley,with an annual budget of aboutf $75M. MSD is dedicated to designing,synthesizing, and characterizing the new materials, and discovering andunderstanding the new phenomena that will propel us into the futurehttp://www.lbl.gov/msd/. The successful candidate will have an excellentnational and international reputation and record of accomplishment.f
The Material Sciences Division Director is responsible for providingscientific leadership for the Division’s research programs as well asenhancing existing programs and developing new programs in materialssciences, condensed matter, experimental and theoretical physics,materials chemistry and biomolecular materials. In addition, will overseetwo major DOE user facilities, two research centers and build collaborativeprograms with UC Berkeley and other research institutions.
For a detailed positiondescription and instructionsregarding how to apply,please visit www.lbl.gov,access the careers page andreference job number 74877.
Berkeley Lab is an affirmative action/equal opportunity employer committed to thedevelopment of af diverse workforce.
As part oft thef University of Pittsburgh’sf strategic expansionof itsf Center forr Energyr (www.energy.pitt.edu), the SwansonSchool of Engineering invites exceptional applicants forendowed faculty positions at allt ranks in the following keygresearch areas:
Energy deliveryy andy reliability, with an emphasis on elec-tric power transmissionr and distribution systems, advancedpower electronicsr technologies (FACTS and DC systems),power systemr modeling andg analysis, power systemr opera-tion and control, and renewable energy integration.
Materials for energy-relatedr applications, with an em-phasis on experimental and/or computationalr efforts onstructural and functional materials used in harsh service en-vironments, and therefore including corrosiong engineering,catalysts, energy storage, thermo-electrics and sensors.
These key areas also complement ourt existingr andg emergingresearch and education activities in carbon managementn andtutilization, unconventional gasl resourcess , and direct energyt con-yversion andn recoveryd .yy
Established as part oft af recent $22t million gift fromt the Rich-ard King Mellong Foundation, a total of fourf endowedr facultypositions are available: two Professor-level appointments asR.K. Mellon Chairsn ins Energyn andy two Assistant/Associate Pro-fessor appointmentsr as R.K. Mellon Facultyn Fellowsy ins Energyn .yy
The successful candidates will greatly benefit fromt the re-sources fostered by the University of Pittsburgh’sf extensivefacilities, research partnerships, and close proximity to nu-merous energy-related companies and research laboratories.For instance,r the Department oft Energy’sf National EnergyTechnology Laboratory (NETL) recently formed a RegionalUniversity Alliance (RUA) for energyr technology innovationthat ist in partnership with the University of Pittsburghf andfour otherr nationallyr recognized universities.
Interested candidates or candidater teams should apply with asingle pdf filef of thef following: a cover letter;r a full curriculumvita; statements describing teachingg andg research interestsand plans; copies of threef representative publications; andthe names and contact informationt for atr leastt threet refer-ences. Questions and nominations should be addressed toProf. Brian Gleeson, Director ofr thef Center forr Energyrat [email protected].
For ther R.K. Mellon Chair inr Energy position, please apply at:[email protected]
For ther R.K. Mellon Faculty Fellow in Energy positions, pleaseapply at: [email protected]
Screening beginsg immediatelys andy willd continuel untile thel searcheis closed.s The Universitye ofy Pittsburghf ish ans Affirmativen Action,eEqual Opportunityl Employer.y
Phenomenex isx a leading provider of advanced technology solutions for separa-
tion science techniques in the areas of sample preparation, high-performance
liquid chromatography (HPLC), and gas chromatography (GC). The company has
the following job openings—Organic Surface Chemist and Sol Gel Chemist.
Organic Surface Chemist will work with R&D team to develop, enhance, or
investigate new and/or existing separation products and technology. Respon-
sible for researching, developing, and controlling sorbents, in particular their
surface modificationfi in order to convey particular properties useful in separation
science. This may include development of new HPLC, SPE, and other separation
science consumables.
Qualifi cations: PhD degree in Organic Chemistry or Polymer Chemistry re-
quired; industry work experience required; extensive knowledge of HPLC and
SPE production; at least fivefi years of experience in synthesis and derivatization
of silica and polymer.
Sol Gel Chemist will support and/or lead R&D efforts in the design and devel-
opment of high performance, sol gel based medias and technologies for use
in liquid chromatography and solid phase extraction.
Qualifi cations: PhD degree in Analytical Organic/Biochemical areas required
(Masters degree will also be considered); at least three years of experience in
inorganic Sol-Gel Chemistry; at least one year of work experience.
Submission of Application: Interested candidates should submit his/her C.V.
For more information about the position, visit www.phenomenex.com/careers.
CHEMISTS
U.S. Citizenship Required.
Equal Opportunity Employer. M/F/D/V.
869MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
CAREER CENTRAL
The Department of Physicsf in the School of Artsf and Sciences an-nounces a tenure-track faculty opening at the assistant professor levelrin Experimental Condensed Matter/Materials Physics. This hire is de-signed to enhance activities within the Physics Department and in a newInstitute for Materialsr Science and Engineering, which will be formallycommissioned in July 2013. The duties of thef position will include, butare not limited to, teaching and advising students, conducting originalresearch and publishing the results, and participating in departmentaland university service. A PhDA degree in a relevant fieldfi is required.Candidates are sought who have highly visible research achievementsand who have a strong aptitude for teachingr and mentoring studentsat the undergraduate and graduate levels. The appointment will beginFall 2013. Information on our departmentr can be found at http://www.physics.wustl.edu.
Applications should consist of thef following: cover letter,r current resumeincluding publication record, statement of researchf interests and plans(up to fivefi pages), statement of teachingf interests and approach (up tothree pages), and names and complete contact information (includingemail addresses) of threef references. Application materials must besubmitted electronically by email as a single filefi in editable (e.g., notpassword protected) PDF format tot [email protected] fullr consideration, applications should be submitted on or beforerNovember 1,r 2012.
Washington University isy ans equal opportunity/equall access/afl fiff rmativefifi action institution.
Women and minoritiesd ares encouraged tod apply.
The Center for Nanoscale Science and Technology (CNST) at
the National Institute of Standardsf and Technology (NIST) in
Gaithersburg, MD anticipates that it will soon have a vacancy
for a Project Leader in the Energy Research Group. The CNST
is a national user facility that supports nanotechnology from
discovery to production by providing industry, academia,
NIST, and other government agencies with access to world-
class nanoscale measurement and fabrication methods
and technology. The expected Project Leader position will
require an exceptional scientist or engineer with a strong
record of creativityf and achievement in the synthesis and
characterization of inorganic-basedf nanomaterials for ap-
plications in batteries, ultracapacitors, solid-state fuel cells,
and related electrochemical energy conversion and stor-
age technologies. The individual should have an extensive
background in chemical and/or materials science or related
disciplines, and a strong interest in developing new instru-
mentation and measurement methods for nanoscale charac-
terization of thef relevant chemical and physical phenomena.
The individual must possess the leadership abilities required
to build a thriving research program; mentor the research
The College of Engineering Sciences, University of Tsukuba, is seeking
a researcher for an appointment at the associate professor level from
1 April 2013 till 31 March 2017. The candidate should have experi-
ence in condensed matter and/or materials research in a broad sense
including soft matter research, either theoretical or experimental. As
part of the university’s drive to further global integration, the successful
candidate is also expected to contribute to English education and science
& engineering education in English at the College of Engineering Sci-
ences, the Graduate School of Pure and Applied Sciences, and through
campus-wide programs. The candidate must have a doctorate degree,
and English must be the candidate’s fi rstfi language.
Applications should be sent by REGISTERED MAIL to: Nobuyuki Sano,
Dean of the College of Engineering Sciences, University of Tsukuba,
Tsukuba, Ibaraki 305-8573, Japan, to arrive no later than October 19,
2012. See application details at http://www.tsukuba.ac.jp/update/jobs/
The Department of Materialsf Science and Engineering at Johns Hopkins University invites applications for ar junior-level, tenure-track faculty positionpreferably in computational biomaterials. Major areasr of interestf include cell mechanics, self-assembly, transport phenomena in biological systems,bio-inspired engineering, and tissue engineering. We will also consider outstandingr candidates in experimental biomaterials. Preference will be givento applicants at the assistant professor level,r but consideration will also be given to exceptionally qualifi edfi candidates at higher ranks.r
Johns Hopkins University offers world-class research and teaching environment in biological and medical sciences with extensive opportunities forcollaboration with the Johns Hopkins School of Medicine,f the School of Publicf Health and the Krieger Schoolr of Artsf and Sciences. Collaborativeopportunities also exist with the Institute of Nanobiotechnology,f the Whitaker Biomedicalr Engineering Institute, the Translational Tissue EngineeringCenter, the Johns Hopkins Engineering in Oncology Center, and the Center ofr Cancerf Nanotechnologyr Excellence.
The successful candidate will be expected to establish an independent, internationally recognized research program and to contribute fully to theundergraduate and graduate educational missions of thef department. Applicants should have a PhD degree or equivalentr in materials science andengineering or ar related fi eld;fi postdoctoral experience is desirable. Candidates must have demonstrated ability to undertake independent, interdisci-plinary, and collaborative research. Additional information about the department may be found at http://materials.jhu.edu.
All applications should be submitted electronically as a single PDF document to [email protected]. Applications should include a cover letterrdescribing the principal expertise and accomplishments of thef applicant, a complete resumé, statements of researchf and teaching interest, and thenames and contact information for atr least three references. For fullr consideration, applications should be received by November 1, 2012.
FACULTY POSITION Department of Materials Science and Engineering and Sheridan Libraries
The Department ist committed tod building a diverse educational environment;l women and underrepresentedd minoritiesd are strongly encouragedy tod apply. The Johns Hopkins University isy an EEO/AA Employer.A
FACULTY POSITION IN ADVANCED MATERIALSSchool of Materials Science and Engineering | College of Engineering, Architecture, and Technology
Oklahoma State University
The College of Engineering,f Architecture and Technology (CEAT) at Oklahoma State University (OSU) seeks applicants and
nominations for a tenure-track position at the assistant or associate professor level. The successful candidate will join an
existing group of facultyf in the Advanced Materials Program housed in the 123,000 square foot Helmerich Advanced Tech-
nology Research Center (HATRC) on the OSU campus in Tulsa. The vision for the HATRC is to be internationally recognized
for advanced materials research, graduate education, and new enterprise development.
Applicants should have research interests which complement thrusts in advanced/nanomaterials useful for energy systems,
biological/medical systems, and information technologies. There is a particular interest in candidates with background in
materials for energy systems such as batteries, fuel cells, and solar energy conversion. Applicants should have an earned
PhD degree in materials science and engineering or ar related field.fi Research experience beyond doctoral studies is desirable.
The successful candidate will be expected to develop an externally funded, internationally recognized research program in
advanced materials; to excel in teaching at both the undergraduate and graduate levels; and to work collaboratively across
the university and State.
Applications should include a letter ofr application;f curriculum vitae; descriptions of twof research projects with plans to secure
external funding; a statement of teachingf interests and philosophy; and the names and contact information of fif vefi references.
Applications should be submitted electronically to [email protected]. Review of applications will begin
immediately and continue until the position is fi lled.fi The target starting date is January 2013 if thef successful candidate is
available. More detailed information about the position and the HATRC may be obtained by visiting the College web site
(http://www.ceat.okstate.edu/).
Oklahoma State University isy an Equal Opportunity/Affil rmativefifi Action/E-Verify Employer.y
871MRS BULLETIN • VOLUME 37 • SEPTEMBER 2012 • www.mrs.org/bulletin
FEATURES POSTERMINARIES
Good reads for the materials researcher
Iread constantly. It is part of who and what I am. Reading, whether fiction or nonfi fiction, is a pleasure and helps me infi
life and in my work. I hereby share with you some recent reads, recommending them to your attention. I understand that some of you will not like any of these books, but I hope that most of you find one or more interesting and useful.fi The fi rst book on my list is fi The New Science of Strong Materials (or Why You Don’t Fall through the Floor) by J.E.
Gordon. This is a classic, first fipublished in 1968, which hasbeen reprinted several times.The edition that I read is in pa-perback published by PrincetonUniversity Press in 2006, with an introduction by science writ-er Philip Ball. The book delvesdeeply into strength, cohesion, stress, and strain. It covers cracks, crack stopping, and dislocations. Chapters addresscomposite materials, wood, ce-ramic, and metals. The book left me with a sense of wonder and
a deep appreciation for research in this area that has improved all of our lives. Next, I recommend the autobiography of Eric R. Kandel,who received the Nobel Prize in Physiology or Medicine in2000 for his work on memory storage in the brain. His book isIn Search of Memory (The Emergence of a New Science of the Mind). This technical autobiography covers details of his lifeas well as research during his lifetime into the phenomenology associated with memory storage and retrieval. These are areas in which I am profoundly ignorant, having overlooked themthroughout my education. Nonetheless, I found the book read-able and enjoyable. Kandel does an excellent job of juxtaposing his work with that of others in the fi eld. The edition that I read fiwas in paperback published by Norton in 2006. Mark P. Silverman has written several highly interesting and readable books. I recommend A Universe of Atoms, An Atom in the Universe. The version that I read was in hardcover published in 2002 by Springer-Verlag. It is a revised version of And Yet It Moves published by Cambridge University Press in 1993.Although the book is a smorgasbord of strange and interest-ing physics, I was most highly interested in his discussions of interference effects using electrons. Joe Jackson has written a marvelous book discussing his-torical events around the race to discover oxygen. The book,entitled A World on Fire (A Heretic, an Aristocrat, and the Raceto Discover Oxygen), follows the lives of Joseph Priestley (the
heretic), Antoine Lavoisier (the aristocrat), and others duringthe time before, during, and after the French revolution. This era saw the rise and fall of the phlogiston theory and its replace-ment with one of the foundations of modern chemistry. Thebook highlights the tragic lives of both of the main protagonists in light of the revolutionary era in which they lived. I read ahardback version of the book published in 2005 by Viking. Giancarlo Ghirardi has written an excellent book about thefoundations of quantum theory. The book, entitled Sneaking aLook at God’s Cards (Unravel-ing the Mysteries of Quantum Mechanics), covers the is-sues raised by superposition,interference, and entangle-ment. Although he discusses the usual topics in vogue inquantum information, includ-ing quantum cryptography,quantum communication, and quantum computers, the meat of the book is the discussion of quantum theory and nonlocal-ity. He highlights the disputes between Einstein and Bohr, particularly related to the famous Einstein–Podolski–Rosen(EPR) paper and Bohr’s response; and discusses hidden vari-ables approaches to quantum theory, philosophical notions such as contextuality, many-worlds theories, and quantum histories.He concludes the book with a study of dynamic reduction ef-forts, including an approach developed by himself, Alberto Rimini, and Tullio Weber. The book is deep in content about thefoundations of quantum theory, but should be accessible to thosewho have had a standard course in quantum mechanics and have knowledge of the Dirac notation of quantum states. The ver-sion of the book I read was in hardback published in Eng-lish by Princeton University Press in 2004. The book was originally published in Italianunder the title Un’occhiataalle carte de Dio (il Saggia-tore, Milano, 1997). I recommend any of the books written by Emil Wolf. I have several editions of Principles of Optics, theclassic work by Born and Wolf, and have used it to my advantage throughout my
career. I recently read Professor Wolf’s book Introduction tothe Theory of Coherence and Polarization of Light. The version that I read is a hardback published by Cambridge UniversityPress in 2007. He treats both spatial and temporal coherence, second-order and higher order coherence effects, phenomena produced by multiple sources with differing states of coherence, coherence effects on polarization, scattering, and a unified treat-fiment of polarization and coherence. The book will be useful to those with a general interest in optics, to astronomers, and to materials scientists who deal with scattering, coherence, and polarization of electromagnetic fields.fi All of my career, I have been fascinated by elementaryparticle physics and the giant machines used by high-energy researchers to understand elementary particles. Sometime agoMichael Riordan wrote a history of the work to establish the quark theory, entitled The Hunting of the Quark (A True Storyof Modern Physics). The work sets the research in place with the personalities involved, from Murray Gell-Mann, Richard Feynman, Geoffrey Chew, Shoichi Sakata, George Zweig,Sheldon Glashow, Abdus Salam, Steven Weinberg, and a host of others. If you have ever wondered about the eightfold way, bootstrapping, S-matrix theory, partons, and quarks, this is ahighly readable history. The version that I read was a paperback published by Touchstone/Simon and Schuster in 1987. Nancy Thorndike Greenspan has written an excellent biog-raphy of Max Born entitled The End of the Certain World (The Life and Science of Max Born). The biography covers both per-
sonal and intellectual aspects of Born’s life and work. The book covers much of Born’s work, but highlights his work on quantum mechanics. Hisrelationships with Albert Einstein, Neils Bohr, Fritz Haber, Werner Heisenberg, Wolfgang Pauli, P.A.M. Di-rac, Max Planck, Pascual Jor-dan, and others are discussed in detail. The backdrop of the rise to power of Nazism and its impact on Born and oth-ers is addressed in detail. The book is highly readable. The
version that I read was a hardback published by Basic Books in 2005. Dietrich Stoltzenberg has written an excellent biographyof Fritz Haber entitled Fritz Haber (Chemist, Nobel Laureate,German, Jew). This book covers both personal and intellectualaspects of Haber’s life and work, highlighting significant areas fisuch as the Haber–Bosch process (synthesis of ammonia, nitro-gen fixation) and the Born–Haber cycle (calculation of lattice fienergies, the energy required to form a crystal from its ions).Haber’s relations with many of the chemists and physicists of that era are discussed in detail, including Albert Einstein, Max Born, Rudolf Stern, Richard Willstatter, Carl Bosch, Carl
Engler, James Franck, Walther Nernst, and Max Planck. Thebook discusses Haber’s industrial affiff liations, his academic fiwork and affiff liations, his Nobel Prize received in 1920, hisfiparticipation in the fi rst World War, and his exile from Germany fiafter the ascension of the Nazi Party. Haber’s life story is filled fiwith intellectual triumph and personal tragedy. The version of the book that I read was a hardback published in 2004 by theChemical Heritage Press.
For an introduction to special relativity, I highly recom-mend N. David Mermin’s book It’s About Time (Understand-ing Einstein’s Relativity). The version that I read is a hardback published in 2005 by Princeton University Press. It covers theusual paradoxes, moving clocks, synchronization of clocks,space-time geometry, and E = mc2. It is highly readable. Michael F. Barnsley has written an excellent book entitled SuperFractals (Patterns of Nature). The version that I read was in hardback published by Cambridge University Press in 2006. The book follows on previous work in iterated function systems to intro-duce new ideas such as su-per iterated function systems and fractal tops. The book re-quires knowledge of at least some calculus and may betruly accessible only to thosewith more mathematicalbackground. Nonetheless,the graphics are spectacular and alone worth the price of the book. The connectionsto real fi gures found in naturefiis amazing. So many of my colleagues have acquired an interest in the programming language called Scientifi c Python that I recently fidetermined to learn to program in this language. Consequently,I am working my way through several books to help: Begin-ning Python (From Novice to Professional) by Magnus LieHetland (Apress, 2008), Python Algorithms (Mastering BasicAlgorithms in the Python Language) by Magnus Lie Hetland (Apress, 2010), and A Primer on Scientifiii c Programming with fiPython by Hans Petter Langtangen (Springer, 2009). Althoughthe books are available in paper, I am reading them on my iPad using the Kindle app. Lest you believe that I am invested only in technical books, I also have some recommendations in fiction. For my friends fiat MRS Headquarters in Pittsburgh, I recommend the fantasy series by Wen Spencer including Tinker, Wolf Who Rules, Elf-home, and others in which a signifi cant part of Pittsburgh hasfibeen transported to be a part of a planet fi lled with elves. If you fiare interested in adventure and mystery, I recommend the Jack Reacher novels by Lee Childs, the novels of Dick Francis, and the Spenser novels of Robert B. Parker.
Steve Moss
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