RESEARCH HIGHLIGHTS 2012
A publication of the WPI Advanced Institute for Materials Research

RESEARCH HIGHLIGHTS 2012

WPI Advanced Institute for Materials Research
The Advanced Institute for Materials Research (AIMR) at Tohoku University in Sendai,
Japan, is one of nine World Premier International Research Center Initiative (WPI)
programs established with the support of the Japanese Ministry of Education, Culture,
Sport, Science and Technology (MEXT). Since its inauguration in 2007, the AIMR has beenbringing together world-class researchers from Japan and abroad to carry out cutting-edge
research in materials science through interdisciplinary collaboration among its fourgroups — Bulk Metallic Glasses, Materials Physics, Soft Materials, Device/Systems — andMathematics Unit.
Led by distinguished mathematician and Director Motoko Kotani, the institute promotesinterdisciplinary research across the different groups while fostering young researchers
through the Global Intellectual Incubation and Integration Laboratory (GI3 Lab), whereinternational joint research is carried out in close cooperation with high-profile researchers
invited from countries throughout the world.
The AIMR is host to over 130 leading researchers, with around half from abroad,including 32 principal investigators. In addition to the research hub at Tohoku University,
the AIMR collaborates with research centers in China, France, Germany, Poland, the UK
and the USA. Close ties with other leading overseas institutes are maintained through its
Adjunct Professor and Associate Professor programs.

AIMResearch
AIMResearch is an online and print publication that highlights the scientific achievements
and activities of the AIMR. First published in June 2009, AIMResearch selects the mostimportant papers from the wealth of research produced by AIMR scientists throughout theyear, distilling the essence of the achievements into timely, concise and accessible researchhighlights that are easy to digest, but retain all of the impact and importance of the original
research article. Published monthly on the AIMResearch website in both English andJapanese, AIMResearch highlights bring the very best of AIMR research to a global audienceof specialists and nonspecialists alike. AIMResearch also publishes a range of features articles
introducing other activities of the AIMR’s research groups. Visitors to the website canregister for monthly email alerts in either Japanese or English to keep abreast of the latest
developments and discoveries made at the AIMR.
research.wpi-aimr.tohoku.ac.jp

MESSAGE FROM THE DIRECTOR
2Integrating mathematics and materials science
RESEARCH HIGHLIGHTSIN THE SPOTLIGHT

6

Thin films: Modulating magnetism

7

Structural defects: Know the boundaries

8

Insulators: Electrons gaining mass

30

A new director, a new direction

9

Graphene oxide: Increased performance through32

Bringing mathematics to life

controlled reduction

34

Young researchers delve deeper into

10

Bulk metallic glasses: An unexpected hybrid

11

Polymer properties: Macromolecular mapmaking

12

Topological insulators: Conduction gets a tune-up

13

Bulk metallic glasses: Nanowire gems in the28

A calculated approach to materials
science researchmaterials science
35

Marrying materials withmathematics

particle dust
14

Oxide materials: Hidden layers

15

Cell imaging: Switching it up

16

Spintronics: Both sides polarized17

Lab-on-a-chip: Electrochemical imaging

18

Biomaterials: Stimulating patterns

19

Catalysis: A kink in the golden rules

20

Bulk metallic glasses: Taking the color out of
polluting dyes

21

Tissue engineering: A scaffold for longer-lasting cells

22

Bulk metallic glasses: Glasses that bend the rules

23

Spin electronics: Mirror, mirror on the wall

24

Oxide materials: A see-through superconductor

25

Ultra-hard ceramics: Open up and toughen up

26

Catalysis: Going for gold

research.wpi-aimr.tohoku.ac.jp
AIMResearch is a publication of the Advanced Institute for Materials Research(AIMR), a Tohoku University institute funded by the Ministry of Education,
Culture, Sports, Science and Technology of Japan.
© 2013 AIMR, Tohoku University. This publication may be reproduced in its
original form for personal use only. Modification or commercial use without priorpermission from the copyright holder is prohibited.

Editorial
AIMR, Tohoku University
2-1-1 Katahira, Aoba-ku, Sendai,
Miyagi 980-8577, Japan
Editor-in-Chief

Motoko Kotani

Managing Editor

Takashi Takahashi

Editorial Assistant

Tomoko Tagawa

ISSN 1884-491X

MESSAGE FROM THE DIRECTOR

Integrating mathematics andmaterials science
As the director of the Advanced
Institute for Materials Research(AIMR), Tohoku University, it
is my great pleasure to welcome
you to the fourth print edition of
AIMResearch: Research Highlights.
A selection of the AIMR’s
distinguished research results
are published monthly on our
website, and this print publication
is a collection of those researchhighlights which appeared in2012. I hope that this issue will
provide you with a comprehensive
overview of our research activities,
as well as an introduction to someof our researchers, our workshops
and our educational opportunities
through our In the Spotlightfeature articles.
The AIMR was launched in2007 under the World PremierInternational Research Center
Initiative (WPI) program by theJapanese Ministry of Education,
Culture, Sports, Science andTechnology (MEXT). True toits name, the program aims tocreate globally visible research
centers within Japan. As one of
the WPI research centers, we aretaking steps to create an ideal
research environment and to
become a hub that attracts andcirculates the world’s best brains
in materials science.
Our efforts have succeededin drawing together an international community dedicated tothe advancement of materials
science. As of April 2012, overseas
researchers made up 55% of all
AIMR researchers. With English
adopted as the official language
and a supportive structure forresearchers in both their researchand daily lives, we provide anenvironment in which overseas
researchers will thrive and feelat home.
Creating new scientific fields is
another important mission of WPI
research centers. At the AIMR,
we are committed to collaborativeand interdisciplinary researchbeyond conventional ideas, andto this end we are pursuing thefollowing objectives: the elucidation of the fundamental principles
underlying the functional properties common to different kindsof materials; the ability to predict
new functions and new materials
based on these newly establishedprinciples; and the creation of“green materials” to contribute tomore efficient “energy harvesting”
and energy consumption as well as
environmental cleanup activities.
Additionally, as the former
director, Yoshinori Yamamoto,wrote in the preface to the 2011
AIMResearch collection, we haveestablished the Mathematics
Unit to further promote thisinterdisciplinary fusion. Since
the inauguration of our institute,
AIMR materials scientists haveobserved and controlled atoms
and molecules using world-classequipment and have discoveredphenomena for which there are
yet no mathematical models. Our
collaboration between mathematicians and materials scientists aims
to provide new insights for breakthroughs in the understanding ofthese and other phenomena.
In this, we are at the forefront ofa global trend. Although mathematics has a long history of serving
as the common language for all
scientific fields, direct interaction
between mathematics and scienceand technology has started rather
recently and is increasingly recognized as key in this computationage. The AIMR is the world’s firstorganization to have initiated materials science driven by mathematics.
In order to promote the mathematics–materials science collaboration effectively, we have set threetarget projects: non-equilibrium
materials based on mathematical
dynamical systems; topological
functional materials; and multiscale hierarchical materials basedon discrete geometric analysis.
These target projects are the resultof our efforts to formalize ourgoals for math–materials sciencecollaborations through joint
seminars, Math–Mate Seminars
and numerous discussions.
These target projects are
now bringing together talented
researchers at the AIMR. For active
advancement of these projects,
project leaders and project subleaders have been appointed in eachtarget project and interdisciplinary
teams have been organized including, of course, mathematicians
and theorists. (The three target
projects and their leadership were
the focus of a 2012 In the Spotlightfeature article, “Marrying materials
with mathematics”, appearing on
page 35 of this collection.) Research
is underway and the project teams
have already produced somepromising results.
By encouraging talented
materials science researchers towork together in new ways, and byincorporating mathematicians as
catalysts, discoveries can progressnaturally from basic science tosocietal applications. I believe that
this exciting and challenging avenueof research — integrated mathematics and materials science — willlead to new breakthroughs inmaterials science at the AIMR.
Motoko Kotani
Director
AIMR

Tohoku University’s Advanced Institutefor Materials Research (AIMR) promotes
fusion research in materials science acrossdisciplinary barriers.
We aim to develop new materials that, rather
than simply fulfilling a need, actually change
the way we look at the world around us.

AIMResearch’s website introduces cutting-edge
research from the AIMR through researchhighlights, spotlights, news and job vacancies.
Access AIMResearch online now!

research.wpi-aimr.tohoku.ac.jp

RESEARCH HIGHLIGHTS
The AIMR advances research in bulk metallic glasses, materials
physics, soft materials and device/systems construction, andactively promotes collaboration among these divisions toward
the development of ground-breaking technologies that crossthe boundaries of conventional fields of study — bridging
the disciplines of materials science, physics, chemistry andprecision, mechanical, electronics and information engineering. The Mathematics Unit further complements the AIMR’s
research activities.

RESEARCH HIGHLIGHTS

Thin films

Modulating magnetism

Thin films of ferromagnetic metals playa pivotal role in a number of spintronics
devices by exploiting the spin of electrons
as well as their charge. A classic example
is a spin valve in which magnetizationof the ferromagnetic metal electrodecontrols the spin of electrical charges.
Perpendicular magnetic anisotropy(PMA) is an essential feature of ferromagnetic thin films which determines
the complexity of magnetic switching
using an external field. Although molecular layers deposited on ferromagnetic films in organic spin valve devices
are known to affect their spin injection
and detection efficiency, much less isknown about their influence on magnetic properties.
Xianmin Zhang from the AIMR andco-authors at Tohoku University have
now demonstrated that capping cobalt
thin films with molecular layers canaffect their PMA to different degrees
depending on the nature of the deposited
molecules1. The results are importantfor understanding the fundamental
magnetic properties of cobalt films,
and are also relevant to spin valves, inwhich molecular layers used as active
elements are placed between electrodesof ferromagnetic metals.
The researchers selected fullerene
molecules — hollow, spherical cages
composed of sixty carbon atoms —along with the aluminum complex
tris(8-hydroxyquinolinato) aluminum,and the linear aromatic molecule pentacene. Molecular layers of varied thickness were applied to cobalt films, andthe team measured the magnetization
loops of all structures under an external
magnetic field positioned either parallel or perpendicular to the film plane.

6© 2012 Miyazaki-Mizukami Group

Molecular layers can strongly affect the magnetic properties of cobalt films throughinterface effects

Schematic representation of a pentacene molecule layer on cobalt film featuring cobalt (gray), carbon(yellow), and hydrogen atoms (red), and spin (denoted with blue arrows).

The data showed a good resemblance
between the loops of fullerene andaluminum complex, but a striking difference in the case of pentacene, which
exhibited a much higher coercive field of
up to 160% more than that of the othertwo molecules.
Zhang and co-workers believe that thedifferent magnetic behaviour observed isdue to a difference in the nature of interactions at the cobalt–molecular layerinterfaces, and they intend to conduct
further experiments to investigate theorigin of these behaviours. As the crystal
structure of pentacene deposited on thecobalt film differed from those of thealuminum complex and fullerene, theresearchers concluded that both thealuminum complex and fullerene arechemically bound to the cobalt film,

whereas pentacene undergoes a processof physical adsorption, a weaker interaction in which the electronic structure of
the molecule remains unchanged.
The results are expected to have an
important impact on future research.
“These findings likely open a new
window to further understand theinteractions at the interface between ferromagnetic metals and molecules or molecular assemblies, and may contributeto the design of new organic-inorganic
hybrid spintronics devices in future,”says Zhang.
1. Zhang, X., Mizukami S., Kubota, T., Oogane, M.,
Naganuma, H., Ando, Y. & Miyazaki, T. Interface
effects on perpendicular magnetic anisotropy
for molecular-capped cobalt ultrathin films.
Applied Physics Letters 99, 162509 (2011).

AIMResearch 2012

RESEARCH HIGHLIGHTS

Structural defects

Know the boundaries

Structural defects play a crucial role indetermining the physical and electronic
properties of materials, and understanding the nature of these defects
is of key importance in correlating
the properties of materials with theirstructure at the atomic level. A thoroughunderstanding of structural defects
requires a precise determination of
their three-dimensional structure andchemical composition. In polycrystalline materials, this goal is complicatedby difficulties in investigating defects
occurring at the boundary between adjacent crystals. Now, Zhongchang Wang
and Yuichi Ikuhara from the AIMR
and other researchers have developed
a method for investigating structuraldefects using a combination of advanced
electron microscopy, spectroscopy andfirst-principles calculations1.
“Natural materials are often polycrystalline and their properties are determined by grain boundaries,” explains
Ikuhara. Grain boundaries — the interface between two crystallite domains or‘grains’ — trap atomic defects such as impurities and vacancies which can induce
complex structural changes. However, it
is difficult to elucidate the distribution
and role of self-trapped grain boundary defects because of their very low
concentration, and the lack of chemical
information obtained from conventional
electron microscopy methods.
To overcome these difficulties, theresearchers devised a methodology thatcombines different scanning transmission
electron microscopy techniques, electronenergy-loss spectroscopy and highprecision density functional calculations.
Furthermore, special care was taken to
design an environment for the electron

AIMResearch 2012

© 2012 Ikuhara Group

Understanding the basis of atomic defects and impurities offers greater insight into
the relationship between the structure and properties of materials

Illustration of an ordered defect superstructure forming at a grain boundary in magnesium oxide. The
superstructure consists of oxygen (red); magnesium (small blue spheres); and impurities titanium (large blue
spheres), and calcium (orange).

microscope that is free from mechanicalvibrations and magnetic fields.
Wang, Ikuhara and colleagues applied
the methodology on magnesium oxide,a technologically important material
that has been studied for decades, but for
which the atomic-scale grain boundary
structure has remained unknown. To
allow the controlled study of individual
grain boundaries, the researchers fabricated a ‘bicrystal’ consisting of two
crystals cut along different crystallographic directions which are joined attheir surfaces.
Electron energy loss spectroscopy andtransmission electron microscopy measurements revealed that titanium andcalcium impurities segregate into thegrain boundary. More importantly, these
impurities interdisperse into the columns of magnesium oxide atoms, giving
rise to a periodic superstructure along
an atomically-straight boundary (seeimage). Comparing the experimental results with the results of the calculations,the researchers were able to pinpoint thestructural transformation leading to astable defect configuration. The analysis
further showed that the calcium andtitanium are bonded to the oxygen rather
than the magnesium atoms.
“This method could in principle beapplied to many types of defects inmany systems,” says Wang. “The main
advantage is that the combination oftechniques allows extraction of atomicscale information on point defects in
defective regions, and provides insight
into the structure-property interplay at
the quantum level.”
1. Wang, Z., Saito, M., McKenna, K. P., Gu, L.,
Tsukimoto, S., Shluger, A. L. & Ikuhara, Y.
Atom-resolved imaging of ordered defectsuperstructures at individual grain boundaries.
Nature 479, 380 (2011).

7

RESEARCH HIGHLIGHTS

Insulators

Electrons gaining mass

Topological insulators are some of themost promising electronic materials
available, because they allow the use of
the electron’s magnetic property — its
spin — for enhanced low-loss computing
technology. This advantageous property
is based on energy states at the surface,where electrons propagate in a similar
way to particles that have no mass.
Takashi Takahashi, Seigo Souma and coworkers from the AIMR, with colleagues
from Tohoku University’s Physics
Department and Osaka University, have
now made the surprising discovery thatin some topological insulators these electrons at the surface state can also show
mass, which leads to entirely new effects
for spin electronics1.
The difference between normal electrons and those in the surface states of
topological insulators is that the lattershow ‘time-reversal symmetry’, whichmeans, for example, that if the motionof electrons was filmed with a camera,
the film would always look the same,
whether it is played forwards or backwards. This time-reversal symmetry isat the core of many attractive propertiesof topological insulators, including theirprotection against losses. One featureof this symmetry is that the surface energy states show a characteristic X-shapewhen electron energy is plotted against
momentum (see image).
The researchers have now studied how
this X-shape evolves in the topologicalinsulator, thallium–bismuth–selenium.
The experiments were performed on
an angle-resolved photoemission spectrometer at the AIMR, which currently
has the highest available energy resolution in the world. During the evolution,
selenium atoms are increasingly replaced

8

From Ref. 1 © 2011 S. Souma

The potential of electron surface states of topological insulators has now been considerablyenhanced by the discovery of surface states with a gap in their energy spectrum

From topological insulator to conventional insulator: the evolution from the topological insulator, thallium–
bismuth–selenium (top left), to thallium–bismuth–sulfur (bottom right), shows that the ‘X’ shape of thesurface states is slowly lost, and a gap in the energy states evolves.

by sulfur. Because the sulfur analogue,
thallium–bismuth–sulfur, is not a topological insulator, the replacement ofselenium by sulfur enables the trackingof the transition from a topological insulator to a classical insulator.
With increasing sulfur content, thesurface energy states slowly begin to
lose their X-shape and a gap opens up
in the center of the ‘X’. This means thatthe electrons no longer appear massless.
“There are predictions that topologicalinsulators with a gap show a coupling
between magnetic and electronic effects, the strength of which is independent of the material,” explains Souma.
This could be of particular relevanceto information storage technologies,
because such an effect allows thecontrol of magnetic information withelectrical fields.
The present study makes a compellingcase for the technological importance of
topological insulators, which continue
to be one of the most intensively studiedmaterials today. “Our next step will beto study the origin of this energy gap,
which remains poorly understood,” says
Souma, adding that an experimental
demonstration of the predicted novel
effects will also be important.
1. Sato, T., Segawa, K., Kosaka, K., Souma, S.,
Nakayama, K., Eto, K., Minami, T., Ando, Y. &Takahashi, T. Unexpected mass acquisition of
Dirac fermions at the quantum phase transitionof a topological insulator. Nature Physics
7, 840 (2011).

AIMResearch 2012

RESEARCH HIGHLIGHTS

Graphene oxide

Increased performance throughcontrolled reduction
Optimized cell performance is achieved through controlling the physicochemical
properties of graphene oxide, leading to intriguing perspectives for bio-applications

AIMResearch 2012

Proteins

Graphene oxide© 2011 Wiley-VCH

The extraordinary physical propertiesof graphene — a single layer of carbon
atoms arranged in a honeycomb lattice — and its derivatives such as graphene oxide, have excited the interest ofscientists and engineers with a view toconstructing efficient electronic devices
with potentially new functionalities.
Graphene-based materials may now
also find applications beyond electronics. Haixin Chang, Hongkai Wu andco-workers from the AIMR at Tohoku
University and institutions in Beijing
and Hong Kong believe that graphene’s
combination of transparency, flexibility and electrical conductivity could
enable a wide range of biological andbiomedical applications.
At present it remains unclear whether
graphene or graphene oxide can be usedin vivo, mostly because their toxicity has
not yet been established. However, thesematerials could in theory be used as
analysis platforms for proteins and cells
in vitro, although the complex interplay
between these materials’ surfaces andcells needs to be better understood
before any applications can be realistically considered. In their study of cells
attached to multi-layer or ‘few-layer’graphene oxide films, Chang, Wu andcolleagues have demonstrated a way to
optimize cell performance by controllingthe films’ properties1.
The most direct way of changing thesurface properties of graphene oxide
is by varying its reduction state. The
team achieved this by reducing pristine
films to various extents using thermal
reduction — a method through which
oxygen-containing groups are progressively removed when heated. Various
aspects of cell behavior were tested

Schematic demonstration of the noncovalent interactions between graphene oxide and cellular proteins.

using three different substrates: nonreduced graphene oxide films, and films
that had been reduced for 90 and 260
minutes respectively.
The researchers first determined
the adsorption of various proteinson the films. They observed that thegraphene oxide which had been moderately reduced for 90 minutes had thehighest adsorption.
This can be explained by considering
the combination of conflicting effects
arising from the high oxygen content.
On the one hand, oxygen promotes
hydrogen bonding with the proteins,which increases adsorption. On theother hand, it also induces electrostaticforces and hydrophobic changes, which
reduces adsorption.

A similar trend was observed in tests
to assess cell adhesion, cell proliferationand cell differentiation. In all cases, thebest results were obtained for moderately
reduced graphene oxide, which the teamascribes to the stronger protein adsorption obtained in those conditions.
These observations could have serious
implications for bio-applications. “Thepresent results open up various possibilities to regulate the biological responses
in graphene-based materials by controlling their reduction state,” says Chang.
1. Shi, X., Chang, H., Chen, S., Lai, C., Khademhosseini, A. & Wu, H. Regulating cellular behavior
on few-layer reduced graphene oxide films
with well controlled reduction states. Advanced
Functional Materials 22, 751–759 (2011).

9

RESEARCH HIGHLIGHTS

Bulk metallic glasses

An unexpected hybrid

The exceptional resilience of bulk metallic glasses (BMGs) combined with theirhigh resistance to corrosion and wear
makes BMGs a highly sought-after material in mechanical applications. With alower thermal conductivity than crystalline metals, BMGs also offer potential
applications in thermal management.
Divided into two general groups, BMGs
are classified as either metal-metal-based
glasses or metal-metalloid-based glasses.
Fundamentally, however, the atomic
structure of metal-metalloid-based glasses is still intriguing and remains a matterof debate among experts in the field.
In metal-metal-based glasses comprising of only metallic elements, their structure maximizes atomic packing. However,the situation is much more complex for
metal-metalloid-based glasses, which
also comprise atoms such as phosphorus,
boron, silicon and carbon that tend tosaturate their charge through covalentand coordination bonds. Because thenumber, direction, and length of thesebonds follow specific rules, they inevitably disrupt the dense packing of the metal
atoms in metal-metalloid-based glasses.
Until now, it has remained unclear
how these contrasting experimental observations can be reconciled. Mingwei
Chen, Pengfei Guan and colleagues fromthe AIMR may have now solved the
puzzle by describing a hybrid between
a covalent-bond mediated structure anda densely-packed icosahedron structure
for a model metal-metalloid BMG,
palladium–nickel–phosphorus1.
“This BMG was actually the first bulk
metallic glass reported in the literature,and so far it still has the best glassforming ability among ternary metalmetalloid alloys,” explains Chen.

10© 2012 APS

A combined experimental and theoretical study reveals a hybrid structure for metalmetalloid bulk metallic glasses that reconciles previously contradicting observations

Atomic structure of the bulk metallic glass, palladium–nickel–phosphorus, comprised of phosphorus (pink);
nickel (green); ordered palladium (blue) and disordered palladium (red).

It was therefore a natural choice forthe team to focus on unraveling thestructure of palladium–nickel–phosphorus. In their analysis, the teamperformed both X-ray diffraction
experiments and ab initio molecular
dynamics simulations. The results suggest that phosphorus coordinates withboth palladium and nickel, while metallic bonding occurs between these two
metallic elements.
The researchers propose the structureof palladium–nickel–phosphorus consists of two types of clusters perfectlyinterconnected, in which tri-capped
trigonal prisms centered on phosphorus
atoms are linked together by nickelcentered densely-packed icosahedra.
This hybrid structure, which satisfies
both the necessity of charge saturation

for phosphorus atoms and the dense
packing requirement for metal atoms,
exhibits the lowest energy achievable inthe compounds and is therefore relatively
disordered, yet stable.
These findings do not only explain
the well-known glass-forming ability of
the alloy palladium–nickel–phosphorus,
but also hold a wider significance inour understanding of the formation of
metal–metalloid glasses. “This may be
a universal structural model for metal–
metalloid glasses,” says Chen. “We havealso found the same packing scheme indifferent alloy systems.”
1. Guan, P. F., Fujita, T., Hirata, A., Liu, Y. H. &Chen, M. W. Structural origins of the excellent
glass-forming ability of Pd40Ni40P20.
Physical Review Letters 108, 175501 (2012).

AIMResearch 2012

RESEARCH HIGHLIGHTS

Polymer properties

Macromolecular mapmaking

The surfaces of polymers — large
molecules comprising repeated structural units — contain special physicalproperties such as adhesion, wetting,and friction. These properties can bequite different from those of the bulk
material, and are difficult to correlatewith the polymers’ molecular structures.
Although modern synthetic strategies
offer much control over molecular structure, finding the optimum polymer for aparticular device or application remainsa challenge. Ken Nakajima, Dong Wangand co-workers1 from the AIMR at
Tohoku University have now succeededin mapping out the surface propertiesof a polymer film using atomic force
microscopy (AFM).
Nakajima describes the concept ofmapping properties with a simple illustration: “Consider painting a colored ink
on a polymer surface — the color will be
more easily erased from areas with lower
adhesive properties.” Polymer properties
such as viscoelasticity and adhesion holdgreat potential in a variety of applications, including automotive manufacturing. “It is clear that this work may bedirectly applicable in the production ofpolymer materials for tires, for which
adhesive and viscoelastic properties areimportant. Indeed, we are currently collaborating with several tire companies inJapan,” says Nakajima.
In the past, measurements of tensile
or shear stress have been used to evaluate adhesive strength and viscoelastic
behavior. These methods, however, area macroscale examination and provide
only an average value of properties. In
contrast, AFM uses an atomically thin
tip attached to a flexible lever to directlyprobe the properties of the surface at

AIMResearch 2012

© 2011 ACS

Probing the surface properties of polymers could help to bridge the gap between
their macroscale properties and their nanoscale structure

1 μm
A map of viscoelastic properties of a tri-block copolymer sample.

the nanoscale. Here the research teamused contact-mode AFM, described by
Nakajima as “a nanomassage” in which
the polymer’s molecular structure
consists of a block of poly(ethyleneco-butylene) sandwiched between two
blocks of poly(styrene) — a tri-block
copolymer. Rather than being homogenously mixed, the polymer moleculesin the bulk are arranged so that ‘blocks’
of similar polymer are close together.
At the surface, this is manifested as apattern of many small polymer ‘islands’(see image). “Our AFM technique allows us to prepare a map of how thesurface properties vary over the surface,”
explains Nakajima.
This technique holds promise in
the mapping of mechanical surface

properties for other types of block copolymer, provided there is a mechanical difference betweenAIM
the
different
RESEARCH
components. “In the future we hope tocharacterize the surface properties ofother materials such as bulk metallic
glasses and biomaterials,” says Nakajima.
“Ultimately we are hoping to establish
a connection between the macroscopic
properties of the polymer and a nanoscopic understanding of structure which
we can then use to evaluate and design
new high performance materials.”
1. Wang, D., Liang, X-B., Liu, Y-H., Fujinami, S.,
Nishi, T. & Nakajima, K. Characterization of
surface viscoelasticity and energy dissipation
in a polymer film by atomic force microscopy.
Macromolecules 44, 8693–8697 (2011).

11

RESEARCH HIGHLIGHTS

Topological insulators

Conduction gets a tune-up

Topological insulators exhibit some of
the most fascinating conductive properties of any material. Although thebulk volume of a topological insulator
does not pass any current, its surface
is highly conductive and the magnetic
spin orientations of the surface currents are relatively easy to preserve.
This unique behavior has stimulated
studies into both the fundamental science behind these properties and applications such as ultralow-power spintransistors. Toshiyuki Arakane, Takashi
Takahashi and colleagues at Tohoku
University and Osaka University have
now developed a topological insulator
material that should aid research inthis area1.
The researchers focused on an outstanding problem in the field: the bulkof a topological insulator often has
defects through which current can flow.
This bulk current can obscure surface
currents whose behavior is the intended subject of the experiment. Previous
work by other researchers showed thatmanipulating the elemental composition of a topological insulator can
reduce its bulk conductivity while
maintaining high surface conductivity.
Arakane and co-workers took thiswork a step further by showing thatmanipulating the composition of a
topological insulator can keep its bulk
conductivity low while also allowing
the surface current to be tuned between
positive and negative charge carriers.
They chose to investigate BSTS — a material made from bismuth, antimony,tellurium and selenium (see image).
BSTS is known to have two types ofcrystal defects: one that contributes
positive charge carriers, and one that

12

© 2012 Toshiyuki Arakane

Tuning the composition of a topological insulator material has allowed scientists
to control its intriguing surface properties while preventing current from leaking
through the bulk

Tunable Dirac cone in topological insulator Bi2-xSbxTe3-ySey. Controlling the composition ratio of Bi/Sb and Te/
Se leads to the change in the filling of Dirac carriers while keeping the bulk insulating nature.

contributes negative charge carriers. Careful control over the relative
amount of each element allowed theresearchers to balance these defects,
thus minimizing the bulk conductivity.
Through angle-resolved photoemission spectroscopy, the researchers revealed that this compositional control
can also be used to adjust the energy ofthe surface charge carriers. They wereable to tune the surface carriers to theDirac energy point, where their concentration fell to zero. Furthermore, theysuccessfully tuned the carrier energy toeither below or above the Dirac energy
point, thus causing the surface carriers
to take on positive or negative character, respectively. In both situations, thebulk conductivity remained low.

According to Arakane, this researchshould allow a variety of exotic quantum effects to be observed. “We expect
to see effects such as the topologicalmagneto-electric effect, the quantum
spin Hall effect and excitonic condensation — all of which have been
proposed theoretically but not yet observed experimentally due to the bulk
carrier problem.” Device applications,says Arakane, would benefit from thinfilm growth techniques, which will be a
future focus of the research group.
1. Arakane, T., Sato, T., Souma, S., Kosaka, K.,
Nakayama, K., Komatsu, M., Takahashi, T., Ren, Z.,
Segawa, K. & Ando, Y. Tunable Dirac cone in the
topological insulator Bi2–xSbxTe3–ySey.
Nature Communications 3, 636 (2012).

AIMResearch 2012

RESEARCH HIGHLIGHTS

Bulk metallic glasses

Nanowire gems in the particle dust

With their unique properties of exceptional mechanical strength, high elasticity, and resistance to mechanical wear,
bulk metallic glasses hold great potential
in the design of micromechanical devices
and nanoscale catalysts. Although the
production of nanoscale metallic glass
structures is already underway, the techniques used are too expensive and timeconsuming to lend themselves to mass
production. Koji Nakayama, Na Chen
and colleagues from the AIMR andthe Institute for Materials Research at
Tohoku University have now discovered
a new, cost-effective technique to produce metallic glass nanowires that yields
at least a few hundred million nanowires
per gram of material1.
Unlike the structure of crystalline metals, metallic glasses have an amorphousand tightly-packed atomic structure,
which makes them tough and resistant
to mechanical deterioration. Metallic
glasses are produced using a melting process, in which the molten liquid requires
a high viscosity, as well as a high “spinnability” — a tendency to form elongatedshapes — in order to yield nanowires.
Nakayama and his team found they
could create these conditions in a process
called gas atomization, commonly usedin the production of metallic powders.
During this process, molten metal flows
from the nozzle of a crucible and meets
high-speed gas at the exit, which breaks
up the metal stream into a variety ofparticulate shapes (see image). By
supercooling the molten alloy below
its melting point, the researchers could
increase the viscosity of the melt stream
prior to the gas atomization process.
Though unremarkable to the naked eye,the atomized products form a metallic

AIMResearch 2012

© 2012 ACS

A cost-effective method for creating metallic powders helps to accelerate theproduction of metallic glass nanowires

nanowire
Gas atomization, a process for making metallic particles, can be used to fabricate metallic glass nanowires.
Molten metal flows from a crucible nozzle and interacts with a high-speed gas to break down the metal
stream into various particulate shapes, including nanowires (inset).

lump that contains a tangle of long metallic glass nanowires with diameters of
50–2,000 nanometers.
“The length to diameter of the wire
(aspect ratio) increases exponentiallywith decreasing temperature below themelting point,” explains Nakayama, whoestablished a “spinnability rule” to predict
how nanowires made from different metallic glasses have an aspect ratio that isdependent on atomization temperature.
The team has so far focused on two
metallic glasses — Zr65Cu18Ni7Al10
and Fe76Si9.6B8.4P6 — but plans to makenanowires that contain important
catalytic elements like platinum andpalladium. “Metallic glass nanowires

will have a significant impact on catalyst
research,” says Nakayama. Since nanowires have a large surface-area-to-volume
ratio, they are more catalytically active
per gram of material — one of the goalsof green chemistry. In future, such metallic glass nanowires may also be formed
from magnetic elements, which could
have useful applications in the design ofminiature devices with a high-frequency
impedance response to a changing
magnetic field.
1. Nakayama, K. S., Yokoyama, Y., Wada, T., Chen,
N. & Inoue, A. Formation of metallic glass
nanowires by gas atomization. Nano Letters12, 2404–2407 (2012).

13

RESEARCH HIGHLIGHTS

Oxide materials

Hidden layers

An important characteristic critical toa variety of technologies is the way inwhich oxide materials trap charges. For
example, hafnium dioxide — used toinsulate transistor gate electrodes — canbegin to fail if charges become trappedin its bulk. Similarly, the effectivenessof zirconium dioxide as a common
catalyst depends on the quantity of
trapped charges. Accurately predicting
the nature of charge trapping in oxides
like these, however, has remained anunmet challenge. Now, Keith McKennaand Alexander Shluger from the AIMRat Tohoku University, along with colleagues from the UK and the USA, havedeveloped a new calculational approachto predict unexpected aspects of charge
localization — and thus trapping —in oxides1.
Calculations of charge trapping generally rely on density functional theory(DFT). The widely used implementations of DFT, however, characterize
electrons as interacting with themselves
electrostatically — a physically incorrect
description. This ‘self-interaction error’leads to inaccurate predictions of charge
trapping in materials. McKenna, Shluger
and colleagues have now carried out
calculations using a version of density
functional theory that includes cancellation of nonlinearity — that is, a correction to the self-interaction problem. This
new insight provides an unprecedented
view into how charges are localized inhafnium oxide and zirconium oxide.
Although usually considered to be
three-dimensional bulk crystals, theresearchers’ calculations predictedthat charges in these materials behave
as if they were constrained to twodimensions. This is because the crystal

14© 2012 APS

A new calculational approach predicts that charges trapped in simple and common
three-dimensional bulk oxides are restricted to two-dimensional sheets

A positive charge (blue) inside the crystal lattice of hafnium oxide is initially dispersed in three dimensions(left). The charge brings about slight distortions in the crystal lattice which causes it to localize to a
two-dimensional sheet (right).

structure of each material consists of alternating layers, in which oxygen atoms
coordinate — or bond — to either threeor four metal atoms. When a positive
charge is induced in the materials, it
induces distortions in the surrounding
crystal lattice, and in turn quickly stabilizes the lattice structure (see image).
The positive charge together with thelattice distortions are referred to asa polaron.
The researchers found that polarons
prefer to stay in oxide layers with triply
coordinated oxygen atoms. Such twodimensional behavior has been muchstudied due to the particular physics it
involves, but it has typically been observed only in complex oxides composedof three or more types of atoms, or atinterfaces between materials. Its observation in a relatively simple binary oxide,made of only two types of atoms, is unexpected and will lead to a new investigative approach of the particular physics
involved. “In addition to the importanceof the theoretical methods themselves,
our predictions may stimulate newstudies of the correlated dynamics andinteraction of positive charges in binaryoxides,” says McKenna.
1. McKenna, K. P., Wolf, M. J., Shluger, A. L.,
Lany, S. & Zunger, A. Two-dimensional polaronic
behavior in the binary oxides m-HfO2 andm-ZrO2. Physical Review Letters
108, 116403-1–116403-5 (2012).

AIMResearch 2012

RESEARCH HIGHLIGHTS

Cell imaging

Switching it up

Electroactive and short-lived species
that are released and consumed bycells, including neurotransmitters andreactive oxygen-based molecules, arecentral to cell metabolism, but theirdetection at cell surfaces and interfaces
remains challenging. A research teamled by Tomokazu Matsue and Yasufumi
Takahashi from the AIMR1, in collaboration with Yuri Korchev from Imperial
College London, has now developed ahigh-resolution, non-invasive imaging
method called voltage-switching mode–scanning electrochemical microscopy(VSM–SECM). The technique, which canbe utilized under physiological conditions, provides high-quality topographical and electrochemical images of living
cells simultaneously.
Many SECM imaging approaches havebeen developed to determine surface
topology and reactivity. However, theyusually measure interactive forces bydirect contact, through the tip of a tinyelectrode that moves across the surface ofthe substrate being imaged — which candamage cell membranes.
Matsue and colleagues have now usedfaradaic current, which is generated by
the reacting electroactive species, tocontrol the motion of the electrode, andcontinuously prevent it from touching
the substrate surface. Moreover, they fabricated nanometer-sized glass-insulated
carbon electrodes that allow for highresolution imaging.
To initiate one measurement, the team
moved the electrode tip towards the surface while monitoring the distance-dependent current created by the hindereddiffusion of the electroactive species as
they underwent reduction. When the tip
current decreased to a level that reflected

AIMResearch 2012

© 2012 PNAS

A state-of-the-art technique that enables simultaneous topographical andelectrochemical imaging of interfaces creates new opportunities for the chemical
mapping of living cells

Topographical image of hair cells acquired by the VSM–SECM imaging technique.

the desired distance between probe andeither the substrate surface or an electroactive molecule, the researchers stopped
the probe and recorded its position. At
each position, the team switched thevoltage applied to the electrode to also
determine the species’ activity. Repeating
this process at several points across thesurface yielded simultaneous topographical and electrochemical images.
Similar to ultra-high resolution images, the resulting maps highlighted thesmall protrusions and wave structures ofskin and cardiac cells as well as elongatedhair cells (see image). Visualization ofcell membrane proteins associated withcancer showed that the protein distribution was uneven and did not matchthe ultra small features observed fromthe topological images — demonstrating the usefulness of VSM-SECM
for chemical mapping at biologicalinterfaces. Simultaneous topologicaland electrochemical measurements havealso enabled Matsue’s team to detect
the release of neurotransmitters fromneurons. Furthermore, the combinationof SECM with fluorescence microscopy
clearly showed the extremities of neurons
at the synapse.
Currently, the researchers are further
exploring neuronal communication
using their new method. “We would
like to map the neurotransmitter releasing sites,” says Matsue. The team is alsoplanning to monitor the release-relatedchanges in neuron topography.
1. Takahashi, Y., Shevchuk, A. I., Novak, P., Babakinejad, B., Macpherson, J., Unwin, P. R., Shiku, H.,
Gorelik, J., Klenerman, D., Korchev, Y. E. & Matsue,
T. Topographical and electrochemical nanoscale
imaging of living cells using voltage-switchingmode scanning electrochemical microscopy.
Proceedings of the National Academy of
Sciences USA 109, 11540–11545 (2012).

15

RESEARCH HIGHLIGHTS

Spintronics

Both sides polarized

Spintronics is an emerging technology which exploits the intrinsic angularmomentum — or, spin — of electrons
for new efficient ways of storing andprocessing information. In contrast,
in conventional electronics only the
charge of the electron has a central role.
A basic requirement for spintronics
devices is the availability of electrons inwell-defined, rather than random, spinstates. Akari Takayama and colleagues
from the AIMR at Tohoku University,
together with collaborators from Osaka
University, have now found an approachto producing such ‘spin-polarized’electrons, with the important featurethat the degree of spin polarization canbe tuned1.
Traditionally, the production of
spin-polarized electrons involved ferromagnetic materials, in which spins arenaturally aligned. For device applications, however, electric fields are often
preferred to magnetic ones. A generalapproach to the electric generation ofspin polarization is through ‘spin–orbit
coupling’, which connects the chargeof an electron with its spin. One manifestation of spin–orbit coupling is the
Rashba effect, in which electrons arepolarized when certain types of asymmetries — typically found at the surfaceof materials — are present.
Takayama and colleagues have studied the Rashba effect in very thin filmsof the metal bismuth. They depositedfilms of thickness ranging from 16 to
80 atoms on a silicon surface. To theirsurprise, they observed in these samples
that the spin-polarizing effect was atwork not only on the surface, but also at
the interface between the metal film andthe silicon substrate (see image).

16© 2012 Akari Takayama

The finding that a spin effect — important in spintronics — can be present at both sides
of a thin metal film suggests a route to a tunable source of spin-polarized electrons

The effect of spin-polarization is seen as expected at the surface of a thin bismuth film (upper plane) but also,
surprisingly, at the interface with the underlying silicon substrate (lower plane).

“This result was unexpected, as thesimple Rashba picture suggests the existence of spin-polarized electrons only at
the top surface of our samples,” explains
Takayama. Furthermore, the effects on
the two sides of the film were found tointerfere with each other. As a result of
this interaction, the degree of polarization decreased when the sample wasmade thinner. “This is the most surprising result of our study: spin polarization
can actually be tuned by varying the
thickness of the film,” says Takayama.
The researchers’ choice of bismuth fortheir study was no coincidence. Spin–orbit coupling is particularly strong inmaterials made from bismuth or otherheavy elements, such as gold or antimony. Now that Takayama and colleagues
AIM ofRESEARCH
have shown that the degree
polarization is tunable through the thicknessof the films used, materials such as
bismuth hold even greater promise for
future applications in next-generation
spintronics devices, for enhancing spinpolarized currents, and for fundamental
studies of novel quantum effects.
1. Takayama, A., Sato, T., Souma, S., Oguchi, T.
& Takahashi, T. Tunable spin polarization in
bismuth ultrathin film on Si(111). Nano Letters12, 1776–1779 (2012).

AIMResearch 2012

RESEARCH HIGHLIGHTS

Lab-on-a-chip

Electrochemical imaging

Traditional methods of culturing cells
for biological and biomedical applications use two-dimensional cell cultures,
typically growing cells on the base ofplastic Petri dishes. In recent years,
however, a three-dimensional (3D) environment has emerged as more appropriate for cell culture as it replicates the
biological milieu. This is particularly
important for embryonic stem cells
which can grow into a variety of different tissue structures (such as bone,nerve, cartilage cells) from 3D embryoid
bodies. Researchers from the AIMR and
the Graduate School of Environmental
Studies at Tohoku University have now
built an electrochemical device thatmonitors the activity and differentiationof stem cells in an embryoid body1.
Usually, scientists label biomolecules
for analysis with fluorescent markers
to identify and quantify their presence.
But labelling molecules may be toxic
or interfere with cellular behavior, andfluorescence levels can be compromisedby autofluorescence (signals fromunlabeled molecules) or quenchingfrom other non-target materials or
liquid turbidity. The electrochemical
device developed by Tomokazu Matsue,
Kosuke Ino and colleagues does not
require these labels, thus removing
these problems.
Electrochemical detection has beenused before. However, this device hasa unique feature. Detection is achieved
using an array of 256 electrochemicalsensors with only 32 bonding pads forexternal connection (see image), placedat the base of deep microwells whichenables spatially-resolved measurements. “This electrochemical sensor
density is the highest in the field of

AIMResearch 2012

500 μm500 μm

Optical image (left) of the embryoid bodies sitting on top of individual sensors. The electrochemical image(right) shows the embryoid bodies detected using the lab-on-a-chip device.

electrochemical lab-on-a-chip devices,”the researchers explain.
The research team quantified cellular
activity from embryoid bodies on thearray by ‘redox cycling,’ whereby alkaline phosphatase activity (a marker forthe differentiation level of embryonicstem cells) was measured by the reduction and oxidation of one of its reaction
products. Potentials of electrodes ineach sensor were set at levels to initiate
redox cycling at a specific location fromwhich the local current signals werecollected and measured.
Interestingly, enzymatic activity as
measured by the electrode device after
a four-day incubation did not increase
as expected, suggesting that the stem
cells had differentiated. The device will
therefore be useful to screen embryoid
bodies’ differentiation levels, and will

provide more quantitative than conventional sorting by morphological analysis.
Furthermore an embryoid body
resting on top of the sensor array was
imaged without cross-talk from molecular diffusion between sensors due tothe microwells. In the next stage of thisproject, the researchers will explore thelimits of this imaging capability.
“We intend to increase the density ofthe electrochemical sensors even further for electrochemical imaging ofa single cell or a single tissue,” saythe researchers.
1. Ino, K., Nishijo, T., Arai, T., Kanno, Y., Takahashi, Y.,
Shiku, H. & Matsue, T. Local redox-cyclingbased electrochemical chip device with deep
microwells for evaluation of embryoid bodies.
Angewandte Chemie International Edition
51, 6648–6652 (2012).

17© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

A high-density electrochemical device has been developed to monitor and image
stem cells in three-dimensional embryoid bodies

RESEARCH HIGHLIGHTS

Biomaterials

Stimulating patterns
Microscopic patterns made of tiny drug-filled polymer spheres stimulate stem cell
growth and differentiation for bone tissue repair

18

Drug-laden polymer microsphere

Teflon stamp

Pressure

Microsphere-based
micropattern© 2012 X. Shi

Bone health hinges on the assembly ofvarious cells, including osteoblasts andosteoclasts, into well-defined functional
structures that manage bone-specifictasks in the body, such as cell growth,differentiation and protein secretion.
However, tumor-induced injuries andother bone-related diseases hinder theseself-regulated, sophisticated tasks. To
address these conditions it is essential todevelop tissue engineering approaches
that direct cell behavior.
Xuetao Shi and Hongkai Wu andco-workers from the AIMR at Tohoku
University, together with colleaguesin Hong Kong and Beijing1, have now
developed patterns that serve as scaffolds for bone regeneration. The patterns
consist of polymer microspheres filledwith drug or protein molecules that are
regularly interspaced.
Prevalent methods for directing cell
behavior exploit either chemical and biological signals or topographical cues, butusing each of these methods separately has
proven ineffective. The former approach
can regulate stem cell differentiation into
specialized cells but does not properly
control cell spatial arrangements, while
the latter faces opposite limitations.
By combining both approaches into
microsphere patterns, the researchers
have now taken advantage of chemicaland physical stimulations at the sametime. The patterns induced an aligned
growth of cells that simulates the native
surfaces of bones and the membraneenveloping their outer surface. “We also
used the microspheres to encapsulate andrelease drug molecules to mimic the invivo bone environment, which contains
various beneficial substances such as
growth hormones,” adds Shi.

Schematic representation of the microsphere pattern manufacturing process.

To create the patterns (see image),
Shi’s team first mixed an organic solution containing the biocompatible,
biodegradablepoly(lactic-co-glycolicacid) polymer with a drug or protein dissolved in water in the presence of emulsifiers. After depositing the resulting
microspheres onto a patterned Teflon
mold and adding a solvent to ensureinter-particle cohesion, the researchers
covered the mold with a Teflon slide andapplied pressure to this lid to obtain thepatterned material.
Initial tests showed that patterns
with narrow grooves between the
microspheres resulted in better cellalignment than wide ones. Moreover,the microspheres efficiently encapsulated and slowly released hydrophilic
and hydrophobic molecules, prompting the researchers to simultaneously
load multiple drugs into them. Stemcells cultured on these multi-drugloaded patterns exhibited high levelsof bone tissue formation markers,
proof of their enhanced differentiation
towards osteoblasts.
In addition to bone repair, this combined chemical–topographical strategy
can be used to study muscle and bloodvessel cells for potential regenerative
therapies of cardiac tissues. “Our future
work will focus on further developing
scaffolds displaying surfaces that mimic
native tissue and drug or gene release
function for organ and tissue regeneration,” says Shi.
1. Shi, X., Chen, S., Zhou, J., Yu, H., Li, L. &Wu, H. Directing osteogenesis of stem cellswith drug-laden, polymer-microsphere-based
micropatterns generated by Teflon microfluidic
chips. Advanced Functional Materials
22, 3799–3807 (2012).

AIMResearch 2012

RESEARCH HIGHLIGHTS

Catalysis

A kink in the golden rules

Twenty-five years ago, nobody thoughtthat gold would have catalytic activity
towards molecular oxygen, because classical thermodynamic principles reject
any chemical reaction between gold
and oxygen. But the discovery that gold
particles smaller than five nanometers
could oxidize carbon monoxide (CO)into carbon dioxide (CO2) at room temperature set off flurries of investigation.
Soon, researchers had harnessed thissize-dependent catalysis for applications
such as decontaminating hydrogen gas
in polymer fuel cells. The underlying
mechanism for this catalytic activity
however remains unclear.
Mingwei Chen, Takeshi Fujita, andco-workers from the AIMR at Tohoku
University, in collaboration with researchers from Japan, the US, the UK
and China, have captured new evidence
that small defects on gold surfaces areactive sites for CO oxidation reactions1.
By developing state-of-the-art techniques to watch surface atomic structures evolve as catalysis occurs, the teamalso discovered that impurity atoms play
critical roles in stabilizing the defectsites — a finding that could boost thelongevity and activity of gold catalysts.
Most nanoparticles require an oxide
support to hold them in place, making
it difficult to pinpoint specific gold catalytic mechanisms. Chen and his teamovercame this problem by studying asubstance known as nanoporous gold.
Produced by electrochemical dealloying of a thin gold–silver precursor film, it has a three-dimensional,
free-standing architecture of curved
nanopores, making it ideal to study
gold catalysis without interference fromother materials.

AIMResearch 2012

© 2012 Nature Publishing Group

High-resolution imaging of nanoporous gold reveals that ‘kinked’ surface defects are
responsible for its high catalytic activity in carbon monoxide oxidation

2 nm
A scanning transmission electron microscopy image showing the stepped surface of nanoporous gold.

The researchers turned to sphericalaberration-corrected scanning transmission electron microscopy (Cs-corrected
STEM) to identify catalytically active
nanoporous gold surface structures.
This technique suppresses lattice distortion effects caused by projectionlenses, providing sub-atomic resolution
capabilities. By carefully controlling gas
pressures within a specially-designed
specimen holder, the team performedin situ characterizations during a COoxidation reaction in an environmental
TEM. “Cs-corrected STEM gives us agreat chance to see the true atomic structure of complex materials,” says Chen.
The team’s high-resolution images
revealed that nanoporous gold’s surface
structure consists of flat, close-packed
terraces separated by single-atom
steps (see image). Along bent portions of the nanopores, these steps fallout of alignment and become ‘kinks’of under-coordinated gold atoms —exceedingly active sites for chemical
oxidation. When the researchers exposed the nanoporous gold to a CO/
air gas mixture, they observed thatthe terrace edges dynamically reconstructed into kinked arrangements, aclear sign that these defects play criticalcatalytic roles. Further experiments
revealed that residual silver impurities
in nanoporous gold preserved the highdensity of kinked defects, ensuring highcatalytic performance.
Chen notes: “Although many theories
have been put forward before, the storyof gold catalysis is simpler than anyone
ever thought.”
1. Fujita, T., Guan, P., McKenna, K., Lang, X.,
Hirata, A., Zhang, L., Tokunaga, T., Arai, S.,
Yamamoto, Y., Tanaka, N. et al. Atomic origins of
the high catalytic activity of nanoporous gold.
Nature Materials 11, 775–780 (2012).

19

RESEARCH HIGHLIGHTS

Bulk metallic glasses

Taking the color out of
polluting dyes
Synthetic dyes with long-lasting, vivid
colors are valuable to both manufacturers
and consumers. However, these attributes
also make it challenging to clean up thesecompounds when they slip into wastewater systems and become pollutants. ‘Azo’dyes, for example, owe their colors tonitrogen double bonds that resist degradation from bacterial or carbon sorption
treatments. Now, Jun-Qiang Wang fromthe AIMR at Tohoku University1 andco-workers in Japan and the US havedescribed a way to degrade azo dyeswith far greater efficiency than current
techniques, using amorphous magnesium–zinc metallic glass powders.
One of the best ways to decompose
azo dyes is by using pure, ‘zerovalent’
metals — in an oxidation state of 0 —such as magnesium or iron to transfer
electrons to nitrogen double bonds andcrack them apart. However, although
zerovalent magnesium is particularly
effective at removing organic contaminants from water, it has poor corrosion
resistance and is eventually consumed
by the aqueous environment. Materials
researchers are thus focusing on finding
low-cost methods to reduce the corrosion of magnesium while retaining its
high reaction efficiency.
Alloying magnesium with anothermetal can enhance its resistance to corrosion, but only if the atoms are mixed
together well. To achieve this, Wang andhis co-workers melted magnesium andzinc atoms in a crucible, and then quickly cast them into thin ribbons of metallic glass. The metal atoms pack tightly
and homogenously in this glassy state,giving the alloy excellent durability.
Then, to convert the magnesium-zincribbons into a form suitable for treating

20© 2012 J.-Q. Wang

Dye molecules that contaminate effluent streams can be efficiently degraded bymetallic glass powders

A high resolution scanning electron microscopy image of a metallic glass powder that efficiently
decontaminates dye molecules from wastewater.

wastewater, the team pulverized theminto a fine powder — an unconventional
approach that has many advantages, according to Wang.
“Powders have much larger surface
areas compared to ribbons, which enhances their reactivity,” he says. “Also,
the powdered form may be injectedunderground to deal with pollutantsin groundwater.”Microscopy experiments revealed
that the magnesium–zinc powder waswell dispersed and did not form aggregates (see image), making it ideal forreacting with synthetic contaminants
in an aqueous solution. The powder
de-colored a solution of azo dye within
10 minutes — clear evidence that themetallic glass completely degradedstubborn nitrogen double bonds.

Wang notes that in addition to a
striking improvement in corrosion
resistance, which the researchers attribute to the alloy’s amorphous atomic
structure, magnesium–zinc metallic
glass powders can decontaminate azo
dyes with reaction efficiencies 1,000
times greater than that of commercial
iron powders.
“These materials can efficiently
degrade organic water contaminants
in harsh, anaerobic environments at acheap price, opening up a broad field
for metallic glass applications.”
1. Wang, J.-Q., Liu, Y.-H., Chen, M.-W., LouzguineLuzgin, D. V., Inoue, A. & Perepezko, J. H.
Excellent capability in degrading azo dyesby MgZn-based metallic glass powders.
Scientific Reports 2, 418 (2012).

AIMResearch 2012

RESEARCH HIGHLIGHTS

Tissue engineering

A scaffold for longer-lasting cells
A semi-natural hydrogel scaffold serves to create highly complex artificial tissues
with long-term cell viability

AIMResearch 2012

Day 1

Day 3
© 2012 Royal Society of Chemistry

Natural tissues are highly organizedstructures, often formed from multiple cell types precisely positioned tocarry out their required roles. Efforts
to mimic these structures in order tocreate artificial tissues — for example,
to help heal parts of the body that havesustained damage from injury or disease — is no simple task.
Recentlydeveloped
techniquessuch as dielectrophoresis use electricfields to position living cells within athree-dimensional matrix; however,trapping the cells in place while ensuring their long-term viability has
proven difficult. A highly biocompatible scaffold material that could solve
this problem has now been identified
by an international team of researchers led by Ali Khademhosseini andTomokazu Matsue from the AIMR at
Tohoku University1.
The researchers selected a semi-naturalhydrogel material based on gelatin —gelatin methacrylate (GelMA) — to use
as a tissue scaffold. Previous studies haveshown that GelMA is a suitable material
for culturing cells. The researchers also
observed that GelMA had the capability
to bypass the typical pitfalls of the mostcommonly used tissue engineering scaffolds. “Owing to its low viscosity and conductivity, we suspected that the GelMAhydrogel could be a promising candidate
for cell manipulation using the dielectrophoresis method,” says Samad Ahadian, amember of the AIMR team.
Testing GelMA in the laboratory,
the researchers confirmed that it was a
suitable matrix within which to guidecells into position using dielectrophoresis. Once the cells were in place, theteam exposed the scaffold to UV light.

Day 5
By using a GelMA scaffold, precisely positioned cells are able to grow over several days of culture.

This triggered a chemical cross-linking
reaction within the hydrogel, whichforms the polymer matrix and traps thecells in place. Using a photomask, theresearchers were able to trap one typeof cell in one part of the polymer before
introducing and trapping a second cell
type within the same scaffold.
Crucially, the cells retain longterm viability after the formation of
the cross-linked polymer, and readily proliferate over several days (seeimage). The natural gelatin on which
the hydrogel is based is responsible forthis high biocompatibility. “The GelMA
comprises natural cell-binding motifs
that support cell adhesion, migration,and proliferation,” explains Ahadian.
“The optimized GelMA concentrationof 5% ensures that there is plenty ofspace for the encapsulated cells to
obtain the nutrients required and repel
wasted products.”
The next step will be to produce
engineered tissues with differentiatedcell types, from neural to muscle cells.
According to Ahadian, the potential
applications extend beyond damaged
tissue repair to include uses in drug
screening models or as bio-actuators.
1. Ramón-Azcón, J., Ahadian, S., Obregón, R.,
Camci-Unal, G., Ostrovidov, S., Hosseini, V.,
Kaji, H., Ino, K., Shiku H., Khademhosseini, A. &Matsue, T. Gelatin methacrylate as a promisinghydrogel for 3D microscale organization andproliferation of dielectrophoretically patterned
cells. Lab on a Chip 12, 2959–2969 (2012).

21

RESEARCH HIGHLIGHTS

Bulk metallic glasses

Glasses that bend the rules

Metals normally have a crystalline
structure — that is, the atoms in thematerial are typically ordered in a
repeating pattern. In contrast, atoms
in metallic glasses are arranged in noparticular long-range order. This disorder endows metallic glasses with a highresilience against deformation, as theylack the natural fault lines along which
crystals tend to break. However, crystalline regions have been found to form insome — but not all — metallic glasses
when the material is bent. Until now,the reason why these crystalline regions
form has remained unclear.
AIMR researchers at Tohoku
University together with an international team led by Alain Reza Yavari
have now undertaken a combined
experimental and theoretical study,
and present a model that explains thisbehavior1. The researchers used an
X-ray microscope to examine a ribbonof the metallic glass, Pd40Cu30Ni10P20. As
the ribbon was bent, crystalline regions
appeared on the side where pressure wasapplied. This behavior had previously
been observed, however the researchers’
use of a high-resolution X-ray microscope enabled a closer, more detailed
look at the crystallization process.
The study revealed that compression
alone is not sufficient for crystallization
to occur. Yavari and co-workers foundthat a wide supercooled-liquid regionis also required to bring about crystallization. This supercooled-liquid regionis the range between the temperature
at which a glassy metal becomes liquid
when heated and the crystallization
temperature (typically, far above room
temperature).
In
Pd40Cu30Ni10P20,
the material studied by Yavari and22© 2012 American Physical Society

The partial crystallization of disordered metals under bending has now
been explained

A diffraction image obtained with an X-ray microscope. This image provides researchers with detailed
information about the properties of a bent metallic-glass ribbon.

co-workers, this region spans about
100 °C. In other metallic glasses, thetemperature window is much smaller,or does not exist at all. Thus, in thosesystems, the phenomenon of crystallization under bending does not develop; instead, cracking and mechanicalfailure occur.
Yavari and his team’s findings may havethe potential for wider application to abroad range of materials. “In our study,
the experimental results fit the theoretical predictions very well. This gives us
confidence in our model, which suggeststhat similar processes should be observable for other chemical compositions,”
explains Yavari. The model provides

important fundamental insights into theproperties of disordered metals, but thefindings may hold practical significancetoo. “It is not fully understood how metallic glasses respond to deformations,”
says Yavari. “Crystallization phenomena,such as the one we described, lead to ahardening of the material, which may infact prevent metallic glasses from failingunder compression.”
1. Yavari, A. R., Georgarakis, K., Antonowicz, J.,
Stoica, M., Nishiyama, N., Vaughan, G., Chen, M.
& Pons, M. Crystallization during bending ofa Pd-based metallic glass detected by X-ray
microscopy. Physical Review Letters109, 085501 (2012).

AIMResearch 2012

RESEARCH HIGHLIGHTS

Spin electronics

Mirror, mirror on the wall

Topology is the study of the fundamental relationships between the propertiesof different objects. It can explain,for example, why a coffee mug shares
similarities with a donut (both have ahole in their structure, and either shape
can be morphed to the other), but nota football. Although topology is often
viewed within a geometric context,
its implications extend much further.
Most recently, attention has focusedupon the interesting properties of
topological insulators.
Topological insulators consist of
an insulating bulk with conducting
surfaces. This unique topology arises
from the time-reversal symmetry of amaterial’s electronic states, in which‘time-reversal’ refers to the reversalof motion through time. “So far, all
known topological insulators are basedon time-reversal symmetry,” explains
Seigo Souma from the AIMR at Tohoku
University. However, together with colleagues from the Physics Department
at Tohoku University and Osaka
University, the research group has now
discovered an interesting class of crystalline tin telluride-based topologicalinsulators whose properties arise from a
combination of both time-reversal andcrystal symmetry1.
In time-reversal symmetry, eventsoccur in the same way irrespective ofwhether time progresses forward or
backward. For topological insulators
this means that some electronic currents
can flow with minimal loss, which has
considerable practical applications for
low-energy devices. The possession ofan additional symmetry, such as crystal
symmetry, can help to support similar
behavior — as is the case for crystalline

AIMResearch 2012

© 2012 Seigo Souma

The discovery of topological insulators whose properties are based on both timereversal and crystal symmetries offers a new approach to electronic devices

Unlike conventional topological insulators, the electronic states of those made from crystalline tin telluride
assume a ‘double cone’ shape.

tin telluride, whose symmetry is basedon the mirroring of its crystal structure
as well as its time-reversal one. The electronic states at the surface of the material assume a recognizable ‘double cone’shape — a tell-tale sign for topologicalinsulators (see image).
“The discovery of crystalline tin
telluride marks a new way of finding
topological insulators,” explains Souma.
However, the finding did not come easily
and required observation of the topological state in samples carefully prepared tominimize crystal impurities, as well as accurate measurement of electronic states,
which was achieved with high-resolution
angle-resolved photoemission spectroscopy — a method that determines theenergy of photo-emitted electrons.

In the future, the team plans to
directly characterize crystalline tin
telluride’s electronic properties to determine if they differ from conventional
topological insulators, a process thatshould aid the fabrication of functional
devices. Moreover, Souma expects thisstudy to be an initial step towards thediscovery of further topologies where
insulators based on other symmetries
could exist, with potentially significant
implications for the development ofelectronic devices.
1. Tanaka, Y., Ren, Z., Sato, T., Nakayama, K.,
Souma, S., Takahashi, T., Segawa, K. & Ando, Y.
Experimental realization of a topologicalcrystalline insulator in SnTe. Nature Physics
8, 800–803 (2012).

23

RESEARCH HIGHLIGHTS

Oxide materials

A see-through superconductor

Oxide alloys exhibit intriguing physicalproperties, such as superconductivity and magnetism, which make thempromising components for a wide range
of devices including transistors and batteries. Control of the stoichiometry ofthese materials is an essential requirement for achieving high performance.
Now, Taro Hitosugi, Takeo Ohsawa andco-workers at the AIMR have studied
the growth of two interesting spinellithium titanate oxides1. Their carefulobservations have allowed them tooptimize the stoichiometry of thesematerials, leading to the production ofsuperconducting thin films which also
have a high level of transparency.
High-quality oxide films are usually produced by a method known aspulsed laser deposition (PLD). The
technique involves hitting a structurally
and compositionally low-quality oxide
alloy with high intensity laser pulses,
so that it vaporizes and subsequently
re-deposits onto a substrate. Hitosugi
and co-workers were particularly interested in LiTi2O4, a spinel oxide known
to exhibit superconductivity below
13.7 K, and its close relative Li4Ti5O12,
which is commonly used as an electrodein lithium-ion batteries.
Previously the researchers observedthat the films obtained by PLD tend tohave much lower lithium content thantheir precursor materials. They also
noticed that the oxygen pressure during
growth plays an important role in the
resulting film’s composition.
The team selected Li4Ti5O12 as a target
for PLD and fabricated various films at
different oxygen pressures in a growthchamber. At high oxygen pressure a
Li4Ti5O12 film was obtained — but at low

24

Lattice atom
(Li, Ti and O)

Light beam

Cooper pair

A schematic illustration of a transparent superconductor showing light passing through thesuperconducting material.

oxygen pressure the lithium content became depleted, resulting in the deposition of LiTi2O4 instead. This means that,
depending upon the oxygen pressure,the thin film growth occurs throughtwo different mechanisms which influence the lithium/titanium ratio and, inturn, the structure and composition of
the material deposited.
The PLD-grown oxide films are of an
exceptionally high quality, as exemplified by the high electrical conductivity,
3x103 S/cm, of the LiTi2O4 film at room
temperature. A transparency of up to
70% makes them particularly promisingfor use in touch screen displays and flat
panel displays, as well as for the realization of transparent electrodes for solar

cells. In addition, they exhibit a superconducting temperature of 13 K — a record
high for such a thin film. The films could
also hold potential for quantum information applications where superconducting
qubits are coupled with photons. As thistemperature is higher than that of liquid
helium (approximately 4 K), this offers
the advantage of using relatively simple
cryogenic techniques to reach 13 K,
boosting application-oriented researchusing transparent superconductors.
1. Kumatani, A., Ohsawa, T., Shimizu, R., Takagi, Y.,
Shiraki, S. & Hitosugi, T. Growth processes oflithium titanate thin films deposited by using
pulsed laser deposition. Applied Physics Letters
101, 123103 (2012).

AIMResearch 2012

© 2012 Taro Hitosugi

A study of the growth conditions of oxide thin films leads to the production of atransparent superconductor with a record transition temperature

RESEARCH HIGHLIGHTS

Ultra-hard ceramics

Open up and toughen up

Despite being hard enough to repel bullets, boron carbide ceramics suffer froma critical brittleness that leads them tofracture at low stress levels. However,an international team of researchers
led by Mingwei Chen from the AIMRat Tohoku University1 has now discovered a way to enhance the durability ofboron carbide by synthesizing it into a‘nanocrystalline’ ceramic with plastic
deformation capabilities. Surprisingly,
this increased toughness arises from the
distribution of small pores and amorphous interfaces — factors that normallyweaken ceramic materials.
Commonly, ceramics are madethrough the process of sintering whichheats compressed powders to a temperature just below their melting point.
Although this produces a very hardsubstance, it also generates a variety of
crystal grain structures, which may act
as fracture initiation points. Chen andhis co-workers decided to take a different approach to synthesis: under a lower
sintering temperature, they used intensepressures to fuse the boron carbide
crystallites into uniform grain sizes,
with the expectation that this would
reduce brittleness.
High-resolution electron microscopy
and X-ray diffraction characterizationof the nanocrystalline boron carbide
allowed the team to observe the finegrained structure of the ceramic. They
were amazed to spot tiny, irregularlyshaped holes — nanopores — throughout, as well as thin, amorphous carbon
layers coating the crystal and nanopore
surfaces. Chen explains that these flaws
probably appear because they cannot becompletely driven away by the reduced
temperatures during sintering.

AIMResearch 2012

© 2012 Nature Publishing Group

Introducing porosity inside super-strong boron carbide ceramics enables thesematerials to bend, rather than break, during mechanical deformation

A micropillar carved from nanocrystalline boron carbide ceramic deforms plastically instead of fracturing
during compression, owing to a distribution of nanopores.

Mechanical experiments revealed
this new ceramic to be tougher than
any boron carbide seen before — able
to withstand indentation pressures of
up to 75% higher than those of conventional materials. Re-examination of thedeformed ceramic showed that while
the crystal grains remained intact, thenanopore population had severely diminished. This led the team to postulatethat the pores and carbon layers help
to lubricate the crystal grains, enablingthem to slide during compression andtherefore tolerate greater pressures.
By carving individual micropillars
from the nanocrystalline boron carbide
ceramic (see image), the researchers
were able to see the effects of indentation
first-hand. At high compression pressures, the micropillars bent plasticallylike a metal instead of shattering — anunprecedented observation for this typeof hard material. “This new plastic deformation mode can effectively dissipate theenergy of crack tips — preventing crack
growth,” says co-author and PhD student
Madhav Reddy.
According to the researchers, the enhanced toughness of the nanocrystalline
boron carbide should benefit applications ranging from cutting tools to bodyarmor. They are currently exploring if
their strengthening strategy can be expanded to other hard ceramics, such as
silicon carbide.
1. Reddy, K. M., Guo, J. J., Shinoda, Y., Fujita, T.,
Hirata, A., Singh, J. P., McCauley, J. W. & Chen,
M. W. Enhanced mechanical properties ofnanocrystalline boron carbide by nanoporosity
and interface phases. Nature Communications
3, 1052 (2012).

25

RESEARCH HIGHLIGHTS

Catalysis

Going for gold
Porous gold catalyst proves useful in the selective reduction of carbon-carbon triple
bonds to double bonds

26

C

C

Nanoporous
gold surface
O
Si

H

N

H

H

C
H

© 2012 Tienan Jin

Nanoporous gold catalysts have recently
gained popularity due to their long lifetime and green credentials. As heterogeneous catalysts — in the solid state anddispersed throughout the reaction mixture — they are convenient to handle, incontrast to homogeneous ones which aredissolved within the reaction medium.
They have proved to be efficient in highly
selective oxidation reactions, such as theconversion of an alcohol group (consisting of a C–OH moiety with a single carbon–oxygen bond) to a carbonyl group (adouble-bonded carbon–oxygen moiety).
Until recently, however, nanoporous gold
was thought to be inactive for reductivehydrogenation reactions.
Tienan Jin and co-workers from the
AIMR at Tohoku University, in collaboration with researchers from Japan and
China, have now shown that this catalyst
can be used in the selective hydrogenation of alkynes to alkenes, where carbon–carbon triple bonds are reduced to
double bonds (see image)1. Interestingly,
the reaction is both chemoselective andZ-selective. This means that in addition
to it not progressing all the way to a single bond, the two hydrogen atoms added
to the alkyne moiety are always placedon the same side of the bond, forming
what is known as a Z-alkene. “The accomplishment of perfect Z-selectivity
and chemoselectivity has previously
been unsuccessful in both homogeneousand heterogeneous catalytic processes,”says Jin.
By replacing homogeneous palladium and platinum catalysts with theheterogeneous nanoporous gold, it has
been possible to obtain higher yieldsof the desired alkenes. “Heterogeneous
catalysts are also more robust than theirC
H

Alkynes can be efficiently reduced to alkenes on a nanoporous gold surface in the presence of organosilane,water and an amine.

homogeneous analogues and have a longer lifetime,” explains Jin. “Additionally,
they can be easily recovered by filtration
and reused several times.”
To produce the catalyst, a thin gold–
silver film, featuring three-dimensionally curved nanopores, was subjected
to electrochemical dealloying. Control
experiments using deuterium-labeled
species revealed that organosilane andwater, the hydrogen sources in thereaction, each contributed a hydrogen.
An appropriate amine additive, such as
pyridine, was also required to preventthe formation of molecular hydrogen.
Jin’s team tested the nanoporous goldcatalyzed reaction on numerous alkynes,
with both terminal (at the end of themolecule) and internal triple bonds. All
showed complete conversion and almost
all provided yields of above 90%.

“It is expected that nanoporous gold
will not only be used in the selective
reduction of various functional groups,
but will also open opportunities forapplications in more complicatedheterogeneous catalytic methodologies
for clean chemical synthesis,” comments Jin. “In preliminary experiments,
we have already succeeded in theapplication of the present catalyst systems to the selective hydrogenationof heteroaromatic compounds andcarbonyl moiety.”
1. Yan, M., Jin, T., Ishikawa, Y., Minato, T.,
Fujita, T., Chen, L.-Y., Bao, M., Asao, N., Chen, M-W.
& Yamamoto, Y. Nanoporous gold catalyst
for highly selective semihydrogenation ofalkynes: remarkable effect of amine additives.
Journal of the American Chemical Society
134, 17536–17542 (2012).

AIMResearch 2012

IN THE SPOTLIGHT
The AIMR has grown rapidly since its inauguration in 2007, now
with over 130 leading researchers from all over the world, including 32 internationally renowned principal investigators whoare charged with pioneering new and innovative breakthroughs
in materials science. The institute is also active in developing
young, promising researchers with a focus on strong crossdisciplinary collaboration and creativity. AIMResearch spotlights
these talented researchers of the present and future, detailingtheir daily research activities and scientific ambitions.

IN THE SPOTLIGHT

Published online date 26 March 2012

INTERNATIONAL WORKSHOP

A calculated approach to materials
science research
The 2012 WPI-AIMR Annual Workshop held in Sendai, Japan on 20–24 February 2012 showed a maturing institutethat is recovering well from the effects of the 2011 Great East Japan EarthquakeT

he WPI-AIMR Annual Workshop
is a focal point of the intellectual
life of the AIMR, and brings together members of the institute fromacross the world to discuss the latest
developments in materials science and thework of the AIMR.
The 5th Annual Workshop, the firstsince the Great East Japan Earthquakethat struck the region on 11 March 2011,
causing widespread damage and loss oflife, was held at the Sendai International
Center from 20–24 February under
the theme of “Cutting-edge Functional
Materials for Green Innovation” andattracted 267 participants from 10
countries. As the research institution
closest to the epicenter of the Great East
Japan Earthquake, Tohoku University
sustained heavy damage to much of its

Current director, Yoshinori Yamamoto, February 201228

equipment. However, the university wasable to resume most of its pre-earthquake
activities in less than half a year due to thecommitted efforts of staff and students,
supported by central government andmunicipal authorities and the determination of the local community to overcome
the disaster. As part of the national effortof reconstruction and regeneration, a
new International Research Institute ofDisaster Science will be opened in 2012 at
Tohoku University.
The 2012 Annual Workshop was also
the first to be held since the opening of
the Mathematics Unit as the fifth researchgroup of the AIMR in March 2011, andthe interaction between mathematics andmaterials science was given a central placein the workshop’s program. The key rolethat mathematics is intended to play inthe scientific direction of the AIMR in thenext five years was mentioned by the current WPI director, Yoshinori Yamamotoin his welcoming address to delegates on
the first full day of the workshop. “Westrongly expect mathematics to accelerate‘fusion’ and interdisciplinary research
between the four existing researchgroups,” said Yamamoto. “This is because
mathematics is able to address fundamental issues from a wide range of researchareas … we believe that interdisciplinary
and fusion research catalyzed by mathematics will lead to an entirely new kindof materials science,” he added.
Yamamoto, who has led the WPIAIMR since its opening in 2007, will
step down as director in April 2012 tobe succeeded by Motoko Kotani, aninternationally recognized mathematician

Incoming director, Motoko Kotani, February 2012

and winner of the Saruhashi Prize, given
to outstanding Japanese women scientists,
which she received in 2005 for her workon Discrete Geometric Analysis of Crystal
Lattices. Kotani is the current deputy
director of the AIMR and head of theMathematics Unit, and will become thefirst female director of a WPI center when
she leads the AIMR from April 2012.
The theme of mathematics-guided
materials science research was also emphasized by Akihisa Inoue, the presidentof Tohoku University, in his opening
speech to the assembled delegates. Inouebegan by praising the work of the AIMR,
which, since its establishment, had “madetremendous efforts to advance research
activities that fuse fields and create new
disciplines while reforming and educating
its research environment.” Inoue also welcomed the challenges and opportunities

AIMResearch 2012

IN THE SPOTLIGHT

offered by the “new mathematical viewpoint” which he foresaw promoting “interdisciplinary and fusion research which
will create a new materials science as well
as developing innovative functional materials” and making a major contribution to
the continuing development of the AIMR
as a “unique and leading hub of the materials sciences in the world.” The enhanced
international character of the AIMR also
won praise from the university president,
who noted that 61 of the 127 researchersat the institute are non-Japanese nationals, and commended the role played by
the 15 WPI-AIMR overseas partners
and the three satellite institutions at the
University of Cambridge; the Universityof California, Santa Barbara and theInstitute of Chemistry at the Chinese
Academy of Sciences.
Inoue also discussed the key role of
the AIMR at Tohoku University, andnoted that through the Tohoku University
Action Plan (the Inoue Plan) the university promises to strengthen the organization of the AIMR to aid its development

as an international research network.
Furthermore he indicated that the university intends to extend its “maximum andcontinuing support” to the center after thecompletion of the WPI program to “establish an advanced institute of materials science as a world-leading center of intellectbased on the achievements of AIMR.”The new focus on mathematicsguided materials science at the AIMR was
also reflected in the academic programof the workshop, which began with aMathematics–Materials plenary session
chaired by Kotani and featured lectureson quantum mechanics, the theory of aperiodic solids and network formation andion conduction in ionomer membranes.
These were followed on the first day by
sessions on bulk metallic glasses, materials physics and soft materials and overthe course of the workshop by sessions
covering other key aspects of the work of
the AIMR, including systems and devices,
soft materials, biodevices and materials
chemistry. In total 39 lectures divided
into 13 plenary and parallel sessions were

presented during the three-day workshop,
as well as a two-day poster session, whichdrew close to 90 contributions from
AIMR researchers in Japan and overseas
on a wide range of cutting-edge materials
science research.
The 5th WPI-AIMR Annual
Workshop was concluded on 24 Februarywith a closing address from the directorin-waiting, Motoko Kotani. In this address, Kotani spoke of her vision of the
AIMR as an institute driven by bottom-up
fusion research guided by a mathematicalunderstanding of the fundamental aspectsof materials science, and indicated anumber of areas as key topics for study,
including non-equilibrium materials
based on mathematical dynamical systems, topological functional materials,
and multi-scale hierarchical materials
based on discrete geometric analysis.
Kotani ended her address by thanking
the organizers, speakers and participants
before inviting all present to join the next
WPI-AIMR Annual Workshop to be heldon 18–23 February 2013.

More than 260 participants from 10 countries took part in the 2012 WPI-AIMR Annual Workshop

AIMResearch 201229

IN THE SPOTLIGHT

DIRECTOR’S INTERVIEW

Published online on 28 May 2012

A new director, a new direction
The AIMR was established in 2007 as one of the inaugural research institutes of the World Premier International
Research Center Initiative (WPI). In April 2012 the institute entered its sixth year of operation, with mathematician
Motoko Kotani succeeding organic chemist Yoshinori Yamamoto as its second director

engineering (MEMS). Using such achievements as a base, the AIMR is now looking to make the leap to the next level ofresearch activity. The recent establishmentof a mathematics unit will play a central
role in this process. Until now, each of theresearch groups at the AIMR has concentrated on discovering new materials intheir own unique fields of expertise, andthey have been very successful in doing
so. We now wish to discover new scientificprinciples based on a fundamental understanding of materials through fusion
research. Mathematics will guide materials
scientists in this approach by simplifying
and giving uniform formulation forcomplex phenomena.
AIMResearch: You mention the increased
use of mathematics in the work of the AIMR.
How does the AIMR plan to integrate mathematics and materials science?

Motoko Kotani, director of the AIMRT

he AIMR was founded in 2007 as
one of the original WPI centers
under an initiative of the Ministryof Education, Culture, Sports, Science andTechnology of Japan and administeredby the Japan Society for the Promotionof Science. In just a few years the institutehas established itself as a leading center ofmaterials research in Japan and is building a growing international reputation.
Now entering its sixth year, the AIMR
is about to embark on a new phase ofdevelopment with a unique and ambitious
mathematics-oriented approach to materials science research. Motoko Kotani, aninternationally acclaimed mathematician
and the institute’s newly appointed director,
talks to AIMResearch about the successes

30of the past and her vision for the future of
the AIMR.
AIMResearch: The AIMR recently celebrated its fifth anniversary. As its new director,
how do you see the institute developing overthe next five years?
Researchers at the AIMR have produced
exciting world-class research across awide range of fields. Based on a longrecord of excellence in materials researchat Tohoku University, the AIMR has
taken a leading role in making importantscientific breakthroughs in the fields ofbulk metallic glasses and spintronics, aswell as developing the areas of nanoporous
materials and microelectromechanical

Bringing together materials science andmathematics is a unique and rather ambitious idea. Initially we will focus on using
an integrated mathematics approach toinvestigate three target materials that havefound recent research success: namely
non-equilibrium materials based on mathematical dynamical systems; topological
functional materials; and multiscale hierarchical materials based on discrete geometric analysis. These are all wide-ranging
themes, and it will take some time to investigate each of them thoroughly. Although
we have formed a number of study groups
to identify immediate, mid- and long-termgoals for each theme, achieving substantial
progress may take five or ten years, or
perhaps even longer.

AIMResearch 2012

IN THE SPOTLIGHT

AIMResearch: One of the goals of the AIMR
is to become a research center that is visibleon the world stage. To what extent has thisbeen achieved and how will the AIMR continue to develop its international presence?
Becoming internationally visible is acommon goal of all centers in the WPI
program, and we’re doing pretty well inthat respect. Surveys carried out by theJapan Society for the Promotion of Science
indicate that name recognition of both the
WPI program and the individual WPI centers is growing, and citation analysis showsthat the number of WPI papers in the top
1% of cited research as a proportion of
their total output is the second-highest in
the world. The AIMR contribution to thisachievement has been substantial; many ofthe papers we publish in top-level international journals go on to be highly cited. We
appealed for international collaborators
during development of the three newmathematics-driven materials research
objectives I mentioned previously. Even
though we set only a short window for
applications, we had a very good response
from scientists outside Japan who wereinterested in working with us. The AIMR
also has 22 overseas partner universities
including three satellite centers at the
University of Cambridge, the Universityof California, Santa Barbara and theChinese Academy of Sciences. We are in
the process of creating joint laboratories
with these institutions and are setting
up more satellite centers to increase ourinternational collaborations and broaden
our global reach.

We are proactive in recruiting outstanding
scientists from overseas to participate in
the work of the AIMR, and this helps us toattract more overseas students. Currently
there are three types of foreign PIs: those
who move here permanently to establish
Japan as their main base of research; those
who set up a sizable laboratory at the
AIMR and spend several months a year
here while maintaining a group in theirhome country; and those based at one of
our partner universities abroad who send
postdoctoral students to work on collaborative projects at the AIMR and thus
form a bridge between the two institutions.
Foreign PIs living abroad typically visit
Japan once or twice a year to meet with
their Japanese counterparts and discussproject progress. The joint laboratories
at our satellite centers play an importantrole in facilitating academic exchange
visits between the AIMR in Japan andpartner institutions in foreign countries.
AIMResearch: One of the aims of the WPI
movement is to change the academic cultureof the center’s home institution. In this context, what influence has the AIMR exerted
on Tohoku University?

Tohoku University understands the special
approach that we take towards researchat the AIMR. We have been given a lot of
freedom to develop the kind of academic
and organizational style that suits us as an
institute. As a result we have implemented anumber of new initiatives, such as introducing a merit-based pay system, allowing staff
to hold dual affiliations — which is rather
unusual in Japanese institutes — and havetaken a number of innovative measures tomake our research and pastoral support
services more flexible and responsive tothe needs of our staff and students. Our
intention is to see how this knowledge
can be applied to the working practicesof Tohoku University as a whole. To thatend we will supply the university with anextensive dossier of our experiences at
the AIMR. We anticipate that many of theinitiatives and protocols established overthe past five years will be taken up by otherparts of Tohoku University, such as theDisaster Control Research Center and therecently established Medical Megabank. We
hope that the work of the AIMR will havea major impact not only on the Japanese
university system, but also on the entire
field of materials science.

AIMResearch: The AIMR has the highest
proportion of non-Japanese researchersamong all six WPI centers. What is the secret
to your success in this area?
All of our ‘principle investigators’ (PI) are
extremely active in the international arena,
which brings the work of our institute to theattention of a global audience. Another important factor is the longstanding pedigreeof Tohoku University in materials research.
Both of these factors are extremely helpful
in attracting high-quality PhD students
and postdoctoral researchers to the AIMR.

AIMResearch 2012

In April 2012 the AIMR entered its sixth year of operation

31

IN THE SPOTLIGHT

ROUNDTABLE INTERVIEW

Published online on 30 July 2012

Bringing mathematics to life
Ambitious plans by the AIMR to develop a new approach to materials science research driven by mathematics offers
the prospect of great advances for materials scientists and mathematicians alike

S

ince its inception in 2007, the
AIMR, as one of the inauguralresearch institutes of the World
Premier International Research Center
Initiative (WPI), has pursued a programof innovative cross-disciplinary researchthat brings together techniques andknow-how from a range of materials
science-related fields. This approach —dubbed ‘fusion research’ — has attracted
the attention of the material science
community and already led to several
important discoveries in the field. Now
entering its sixth year of operation, the
AIMR has embarked on a new research
trajectory, with the introduction of an
ambitious program of mathematicsdriven materials research.
The new approach is thought to be
the first of its kind in the world, andis based on harnessing the power ofmathematics to answer fundamental
questions in material science to open
up new areas of investigation in the field
and to guide AIMR scientists in the mostpromising research directions. Although
this bold initiative has the potential to

Natsuhiko Yoshinaga, Mathematics Unit

32

Left to right: Takeshi Fujita, Natsuhiko Yoshinaga and Daisuke Hojo

deliver important new advances, challenges remain in applying the approachto concrete research goals.
To gain insight into some of the challenges and future directions of research at
the institute, AIMResearch talked to three
young AIMR faculty members charged
with the task of developing mathematicsdriven materials science as part of theircurrent research programs.
Merging ideas
Natsuhiko Yoshinaga is an assistantprofessor in the AIMR Mathematics Unit
and a specialist in the mathematics of softcondensed materials. He is optimistic
about the prospect of merging materials
science and mathematics, while also
recognizing the potential challenges thatlie ahead. “The new approach is very
interesting because it brings together twoquite radically different styles,” he says.
“Traditionally, materials science researchis largely empirical and involves a great
deal of trial-and-error. By contrast,
mathematics is all about setting clearlydefined parameters, then building andtesting theories. Mathematics can help
materials science research by providing
mathematical tools to help make sense ofexperimental results.”
Bridging differences in the two distinctive research cultures is considered to
be key to the success of the new strategy,
and careful selection of research goals
is crucial. To this end, initial efforts
will focus on three research areas: nonequilibrium materials based on mathematical dynamical systems; topological
functional materials; and multiscale hierarchical materials based on discretegeometric analysis that the AIMR has

AIMResearch 2012

IN THE SPOTLIGHT

identified as being particularly suited tothe mathematics-driven approach.
Some existing research themes at the
AIMR are more likely to bear early fruit
than others. Takeshi Fujita, associate
professor of the Bulk Metallic Glasses(BMG) Group, shares his views on howmathematics can add value to his areaof specialty: “Bulk Metallic Glasses are agood candidate for mathematics-driven
research,” he explains. “Our work already involves a lot of calculation — forexample, when investigating the effect ofpacking patterns on the properties of newmaterials. We expect that working withour colleagues in the Mathematics Unit
will help to identify the most promisingresearch leads and increase the speed atwhich we can realize new advances.”
Assistant professor Daisuke Hojo,a soft materials specialist in the Soft
Materials Group at the AIMR, also sees
great potential for the new approach. “We
are currently researching the dispersive
behavior of nanoparticles smaller thanten nanometers in non-polar solventsand building three-dimensional modelsof these systems,” he explains. “We want
to use mathematics in our group to investigate how distribution of electric charges
in the particles changes with structure.
We are also examining the effect of different dispersion models on structure basedon mathematical calculations.”
Brainstorm Friday
In addition to singling out specific problems in materials science for

Takeshi Fujita, Bulk Metallic Glasses Group

AIMResearch 2012

mathematics-driven treatment, the AIMR
is spurring further integration of the two
disciplines by encouraging “cultural exchange” between members of the mathematics group and other researchers at theinstitute through free discussion. As partof this initiative, researchers give informal
talks on their research fields at a monthly
event known as the “Friday Seminar” tocolleagues from across the AIMR, as wellas members of the Interface Unit, a groupof theorists in physics and chemistry,
set up as a bridge between mathematics
and experimental materials scientists.
Such activities offer an important way
of connecting researchers with the wider
mathematics community at Tohoku
University and the Applied Mathematics
Forum, an informal grouping of Tohoku
University mathematicians.
Seminars focus on introducing fundamental principles in each field as wellas presenting new research results, withthe aim of helping colleagues from othergroups at the AIMR to gain a deeper understanding of the general background toa research field. The sessions are purposelyinteractive, and joining in discussions andasking questions are positively encouraged.
In addition to discussion seminars
and the weekly “Friday Tea Time” poster
sessions for which the AIMR is wellknown, researchers are encouraged tointeract informally as much as possible.
“Brainstorming is a very important way
to help mutual understanding of the different ways in which materials scientists
and mathematicians see the world,” says
Hojo. “In our group, we meet with colleagues from the Mathematics Unit oncea week to chat about what we’ve been
doing, often without any formal focus.
This kind of free discussion can leadto potentially interesting new ideas forexperiments, or ways of improving ourtheoretical models.”
Yoshinaga adds, “Being able to interact
with researchers from a different discipline on a daily basis is very stimulating.
More often than not, we don’t have a fixedmathematical solution for problems inmaterials science, and so we need to work
closely with our colleagues to develop a
new approach or a different model. Some

Daisuke Hojo, Soft Materials Groupof the materials science research carriedout here links in with really cutting-edge
pure mathematics. Although we have
only been working together for a shorttime, we have made a number of interesting advances in mathematics as well.”
Speeding progress, opening doors
The collaborative spirit that underlies
fusion research at the AIMR has been a
key theme from the very beginning, andnow, with the addition of mathematics, this approach is being taken to thenext level. Greater interaction between
fields also opens up the possibility for
researchers to publish papers in journals
traditionally regarded as being out of
their areas of specialty, leading to the
exposure of their work to a more diverse audience.
“It is important to select research
themes carefully,” says Fujita, “but if we
get that right, then application of themathematics-driven approach should
accelerate progress and increase ourscientific output, as well as opening up
brand new research fields.”
By melding materials science withmathematics in this way, the AIMR
continues its tradition of innovative
fusion research directed at establishing
new research frontiers, building on multidisciplinary exchanges, and ultimately
developing breakthrough technologies forthe benefit of the scientific communityand human society.

33

IN THE SPOTLIGHT

SUMMER SCHOOL

Published online on 27 August 2012

Young researchers delve deeper intomaterials science
23–29 July 2012: The AIMR hosted an English-based Summer School program for international graduate students in
Sendai, Japan

Students, supervisors and staff at the ASSM2012T

he AIMR at Tohoku University
recently welcomed 30 graduate level
students from around the world –representing 13 different nationalities – toSendai, Japan to learn from top materials
science researchers at the 2012 WPI-AIMR
Summer School of Materials Science(ASSM2012).
This one-week English-based summer
school program, held over 23–29 July 2012,is a recent international initiative organizedby the AIMR that will likely have an integral role in the institute’s continued efforts
to develop the world’s next generation ofleading researchers. It offered up-andcoming scientists and outstanding graduate
students in fields such as physics, chemistry,materials science, electrical engineering,
precision engineering and mechanicalengineering a glimpse into materials science research and technology at the AIMR,
hands-on experience using the institute’s
cutting-edge experiment equipment, andthe opportunity to build a global networkwith AIMR researchers and other students.
Originally scheduled to be launchedlast year, the program was cancelled dueto the Great East Japan Earthquake, but

34

received almost 200 applications this year
from Master’s and PhD students all over
the world wishing to attend. A selection
committee made up of AIMR researchers
carefully selected participants based on
their academic background and motivation
for joining the program.
With a theme of “Advanced Materials
to Build a Better Future,” the program
consisted of morning lecture sessions
given by the principal investigators of eachof the AIMR’s four main research groups(Soft Materials, Materials Physics, Device/
Systems Construction and Bulk Metallic
Glasses), followed by afternoon laboratory sessions in which pairs of students
performed various experiments under thesupervision of AIMR researchers.
AIMR Director Motoko Kotani officially commenced the summer school on
the afternoon of 23 July with an opening
address, in which she explained the aim ofASSM2012 is to offer students “a fruitfuland productive opportunity to experiencehigh-level and advanced research,” andemphasized the importance of bringing
young scholars together to build networks
for future research. “These networks will

be indispensable for humans as they tackle
many complicated obstacles, which are
unprecedented in the history of the humanrace. I believe the foundation of the AIMR
networks is composed of the networks
formed among students and researchers.”
Spending the next four days with someof the world’s top materials science researchers gave the students a valuable opportunity to do just that. Professor Kazue
Kurihara, principal investigator of the Soft
Materials Group and current president of
the International Association of Colloid
and Interface Scientists, delivered the firstlecture of the week on Tuesday morning by discussing the measurement of
surface forces for nanomaterials scienceand technology.
After each lecture, students proceeded
to four-hour laboratory sessions on topics
that ranged from making nano-sponge
metals to fabricating hydrogels for cell
encapsulation and drug delivery. This balance of classroom instruction from leading
researchers with laboratory time using
advanced equipment exposed the students
to many fascinating aspects of materials science and introduced them to the researchgoals and achievements of the AIMR.

AIMR researchers supervised summer schoolparticipants in various laboratory sessions

AIMResearch 2012

IN THE SPOTLIGHT

Students presented their work over the last two daysof the ASSM2012

The following days featured morelectures from renowned researchers.
Professor Katsumi Tanigaki of the Materials
Physics Group spoke on the functions ofnanomaterials and their industry applications, while Professor Terunobu Miyazakiof the Device/Systems Construction
Group discussed the importance ofmagnetic materials and how magnetism
can be understood intuitively. Tanigaki is
a former research leader at NEC known
for his contributions to superconductivity
research, and Miyazaki is the pioneer oftunneling magnetoresistance (TMR) andthe 2009 recipient of the Oliver E. Buckley
Condensed Matter Prize of the American
Physical Society, considered the mostprestigious award in the field of condensed
matter science.
The final lecture of the course was given
by Professor Alain Reza Yavari of the Bulk
Metal Glasses Group, who in 2011 received
the Award for Scientific Excellence fromthe French National Center for Scientific
Research (CNRS). One of the highest
ranking researchers at CNRS, his lecture
covered metallic glasses from bulk metallic
glasses down to a microscopic scale.
After the lecture and laboratory sessions wrapped up on Friday afternoon,
the students prepared for a full weekend of
discussions and presentations to conclude
the intense week of learning, but not
before experiencing a slice of Japaneseculture by painting kokeshi (traditional
handmade Japanese dolls) at the Zao
Royal Hotel.

ROUNDTABLE INTERVIEW

A closing ceremony was held after the
final presentations and discussions on
Sunday afternoon, where students were
presented with certificates of successful
completion of the course. It marked theend of a productive week for the students
and AIMR researchers, one that helped
the AIMR and Tohoku University to carryout their commitment to supporting thedevelopment of young researchers aroundthe world.

Director Kotani (right) presented students withcertificates marking their successful completion of
the summer school program

Published online on 26 November 2012

Marrying materials with mathematics
By bringing different areas of materials science together and now building bridges with mathematics, the AIMR is
stepping out in a truly original direction. Where to? A definite answer is not expected for another several years, but
clues are already emerging

S

ince its launch in 2007, the AIMR
has unwaveringly encouragedmaterials scientists with different
backgrounds, expertise and research interests to work together. “This approach stems
from the idea that it is not sufficient togather a collection of excellent researchers
to achieve truly original research,” explains
Masaru Tsukada, the AIMR’s administrative director. “Much can be learnt fromcrossing frontiers,” says Mingwei Chen,
the Target Project (TP) leader of the Nonequilibrium Materials project. Entering thesecond 5-year phase of its development, theAIMResearch 2012

AIMR is building on its ongoing ‘fusion
research’ by taking another significant step:
incorporating mathematics.
Integrative and targeted
The AIMR has established three ‘target
projects’ (TPs) that combine materials
science research expertise with topics ofinterest to mathematicians — namely,
Non-equilibrium Materials Based on
Mathematical Dynamical Systems,
Topological Functional Materials andMulti-scale Hierarchical Materials Basedon Discrete Geometrical Analysis.

Chen explains that a good understanding of non-equilibrium phenomena
relies on mathematic dynamics. Tadafumi
Adschiri, the TP leader of Multi-scale

Masaru Tsukada, the administrative director of the AIMR

35

IN THE SPOTLIGHT

Hierarchical Materials, agrees: “What weare embarking on with our mathematician
colleagues is the analysis of the materials’
properties — from our characterization,
but from a mathematics point of view.” A
longer-term goal is to close the loop backfrom mathematics to materials, and use themodels to predict which materials should
be synthesized for specific uses.
Hierarchical materials are also particularly intriguing for mathematicians, as
understanding the behavior of atoms does
not easily translate into an understandingof a material’s properties. Taro Hitosugi,
sub-leader of the Multi-scale Hierarchical
Materials project, elaborates: “As the atoms
aggregate into clusters and extended
materials, different properties emerge — inthe same way that cells form organs, andorgans form human bodies. What we are
now trying to do, together with mathematicians, is to establish a link between theatoms (discrete points) and the bulk material (a continuum).”
This mathematics-driven approach
may lead to a conceptual revolution of theresearch interests of topological functional
materials. Katsumi Tanigaki, the TP leaderof the Topological Functional Materials
project, works on semiconductors, forwhich inorganic materials such as silicon
have traditionally been used. With flexible
semiconductor devices being touted as thenext technological target, inorganic-based
semiconductors may no longer be the best
choice. “For big changes we need new ideas,
both from theory and experiments,” says
Tanigaki. “We are now trying to use organic-based semiconductors for spintronics aswell as electroluminescent devices in placeof inorganic semiconductors, and we have
had some success. The theory part is where
we’ll work with mathematicians.”“The AIMR’s mathematics-driven
strategy provides an important framework
which guides the projects in a particular direction,” Tanigaki continues. “This is a challenging approach that may well enable us tofind something very original and exciting.
Marrying materials with mathematics likethis is a brand-new area.”Interfacing between disciplines
In the target projects, the traditional approach to collaboration is reversed: the36mathematicians and materials scientists
first team up together, then search for acommon interest and identify a project thatcan benefit both parties.
Even when a suitable project has been
identified, challenges can arise. Specialist
terminology, for example, varies across thedisciplines, which can hinder communication. To address this, the AIMR hosts a
series of informal, interdisciplinary teammeetings where researchers can learn more
about each other’s discipline and researchinterests. When each member presents theirown research, common interests and novel
research avenues emerge. In the Multi-Scale
Hierarchical Materials project, for example,
Hitosugi is fascinated by interfaces at theatomic level whereas other project members are interested in the continuum of bulk
properties. “These differences, and how to
get passed them, is the essence of the target
program,” he says. “It is a good chance for
us to go in a totally new direction.”
The AIMR has also enlisted the helpof ‘interface researchers’, theoreticalphysicists and chemists who do not belong
to any specific research laboratory, but
can freely collaborate with any group.
According to Adschiri, they play themost important role in bridging the gap
between disciplines. Tsukada explains:“They can communicate efficiently withboth parties, thus efficiently conveying
messages and connecting people.” New to
the AIMR, these independent researchers
are already facilitating communication.
Blurring borders
Concomitantly, working on the target projects has started to influence the researchers’
methods in their own, more ‘conventional’
research. Tanigaki notes that this unusual
collaboration is already impacting the way
his team works — before they characterizedmaterials and looked for ways to improvethem, but now they employ modeling as
well. He adds: “What interests mathematicians in topological materials are the topology and geometry aspects, not whether it isinorganic or organic, and working with thisin mind is very interesting.”
Chen is also excited that he has beenable to expand his work, modeling a varietyof glasses and working towards establishing some universal rules. “By broadening
our interests we have also started to workon porosity — a pretty intriguing new
direction,” he says. Such interdisciplinary
research provides invigorating challenges, especially for younger researchers
who are still establishing their own research progression.
“We are waiting for that big result thatwill be our success story,” says Tanigaki.
As such major achievements usually takeyears or decades of research, the AIMR’s
5-year mathematics-focused initiative
presents AIMR researchers with anotherchallenge as they aim to produce results in
a compressed timeframe. Each year the TPs
are required to achieve fixed goals, and the
AIMR monitors their progress in reachingthese annual targets. In these early stages,
it is encouraging that some milestones
have already been reached and joint papers
between materials scientists and mathematicians have been published.
“All researchers agree that the AIMR
is embarking on a bold strategy and it
is difficult to forecast the results,” summarizes Chen. Tsukada agrees that it isa very ambitious project, something thatthe program committee members of theWorld Premier International ResearchCenter Initiative (WPI) recognize. “Itis a challenge, but we believe it will leadto some utterly original and excellent
research,” says Tsukada. 

Left to right: Masaru Tsukada, Mingwei Chen, Taro Hitosugi and Katsumi Tanigaki

AIMResearch 2012

Advanced Institute for Materials Research
Tohoku University