RESEARCH HIGHLIGHTS 2014
A publication of the WPI Advanced Institute for Materials Research

RESEARCH HIGHLIGHTS 2014

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,
Sports, Science and Technology (MEXT). Since its inauguration in 2007, the AIMR has
been bringing together world-class researchers from Japan and abroad to carry out cuttingedge research in materials science through interdisciplinary collaboration among its fourgroups — Bulk Metallic Glasses, Materials Physics, Soft Materials, Device/System — andMathematics Unit, with further integration supported by its Interface 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 150 leading researchers, around half of whom come fromabroad, including 30 principal investigators. In addition to the research hub at Tohok­­u
University, the AIMR collaborates with research centers in China, France, Germany, Poland,
the United Kingdom and the United States. 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
the year, distilling the essence of the achievements into timely, concise and accessible
research highlights that are easy to digest, but retain all of the impact and importance of theoriginal research article. Published monthly on the AIMResearch website in both English
and Japanese, AIMResearch research highlights bring the very best of AIMR research to a
global audience of specialists and nonspecialists alike. AIMResearch also publishes a rangeof feature articles introducing other activities of the AIMR’s research groups. Visitors to thewebsite can register for monthly email alerts in either English or Japanese to keep abreast of
the latest developments and discoveries made at the AIMR.
research.wpi-aimr.tohoku.ac.jp

MESSAGE FROM THE DIRECTOR
2Creating a global community of research collaborators
in mathematics and materials science
RESEARCH HIGHLIGHTS

6

Tissue engineering: Strong hydrogel carries current

7

Solar cells: The benefits of separation

8

Biomaterials: Carpeting the way for

IN THE SPOTLIGHT
28

Materials–maths fusion researchenthuses symposium attendees

30

less-invasive treatments

Exporting mathematics–materials
collaboration research to the world

9

Bioimaging: A sharper view of teeth

32

10

Catalysis: Pinning down degradation

showcases materials science

11

Materials: Polymer chains singled out

innovation at E-MRS Spring Meeting

12

Oxide interfaces: Blueprint for a super-material

13

Material defects: Down to the core

14

Nanomaterials: Tiny flakes with a brilliant future

15

Nanodevices: Molecular motor powers shuttle

16

Nanoparticles: Stretching water droplets

17

Spintronics: Tuning materials for improved

34

World-leading WPI initiative

Material benefits from
US connections

36

The AIMR’s reforms positively
impact Tohoku University

38

Reinforcing a strong andfruitful friendshipmemory performance18

Nanomaterials: Graphene grows up

19

Nanomaterials: Building bone

20

Ionic liquids: Going with the flow

21

Graphene: Finding catalytic success withthree-dimensional nanopores

22

Polymers: Nanoscale nudges reveal critical clues

23

Biosensors: A gentler route to hydrocarbon electrodes

24

Graphene: Customized from the bottom up

25

Electrochemistry: Mapping a battery electrode26

Microscopy: Ultrasharp probing of solar cells

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.
© 2015 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

Creating a global community of
research collaborators in mathematics
and materials science
As the director of the Advanced
Institute for Materials Research(AIMR), Tohoku University, it is
my great pleasure to share withyou the sixth print edition of
AIMResearch: Research Highlights.
AIMResearch highlights the bestof the AIMR’s research through abilingual English–Japanese website.
This print collection compiles all
the research highlights and featurearticles published online in 2014. It
provides an overview of our scientific achievements and introduces
our researchers and activities.
The AIMR was established in2007 under the World PremierInternational Research Center
Initiative (WPI) program initiated by the Japanese Ministry of
Education, Culture, Sports,
Science and Technology (MEXT)
to support the development ofworld-class research centers inJapan. Since its foundation, the
AIMR has been actively conducting research and creating newmaterial systems. We strive tomaintain our standing as a global
center for materials science withan attractive research environment
for the world’s best minds.
The AIMR pursues collaboration between mathematics andmaterials science to accelerateinterdisciplinary fusion and to
explore new materials science bygenerating theoretical predictions.
Such institution-level collaboration is unprecedented and has
invited significant interest fromboth the materials science andmathematics communities.
Mathematicians and experimentalists at the AIMR conduct joint
research, discuss problems anddevelop new models together,which has led to remarkableprogress, as evidenced by the
many published papers with amathematical viewpoint in highimpact journals.
In 2012, to clarify the goalsof our mathematics–materials

science collaboration, the AIMR
set up three Target Projects:
Non-equilibrium Materials basedon Mathematical Dynamical
Systems; Topological Functional
Materials; and Multi-scale
Hierarchical Materials based on
Discrete Geometric Analysis.
This year, we started working in
earnest on a fourth project, CoreTechnology for Nano Energy
Devices. By applying the resultsof the three fundamental projects,
this fourth project aims to produce
new devices and systems that will
directly benefit society.
Ultimately, the AIMR’s goals are
to deduce scientific principles forcontrolling atoms and molecules
based on theoretical predictions
and to create new functional
materials, devices and systems thatwill enhance the safety and qualityof life for communities.
The AIMR has implemented
several organizational reforms,
which have contributed to itbecoming a world-leading institutefor materials research. This year,
Tohoku University set up theOrganization for Advanced Studies(OAS) to promote the internationalization of the university and its
world-class advanced research. The
AIMR has become the first member
institute of this organization.
Furthermore, Tohoku University
will create a research reception
center at the OAS by applying theaccumulated knowledge of the
AIMR. The AIMR and its researchers will play a central role in allthese initiatives, leading Tohoku
University in promoting researchand globalization. I am particularly
gratified by the fact that AIMR’s
experiences have become a driving
force for promoting system reform
and internationalization throughout
the university. The reforms havecreated ripple effects acrossthe university.
As for international partnerships
in 2014, the AIMR establisheda joint research center with the
University of Chicago (USA),expanding on its existing
partnerships with the Universityof Cambridge (UK), the Instituteof Chemistry at the Chinese
Academy of Sciences (China) andthe University of California, Santa
Barbara (USA). Through these joint
centers, we aim to develop a systemthat focuses on implementing
research conducted together withleading materials-science research
institutes. This year, we held joint
workshops with the Universityof Chicago and the University ofCambridge. Moreover, the AIMR
jointly organized a workshop withother WPI centers at the 2014
Spring Meeting of the European
Materials Research Society, which
was a great success.
In the eight years since its inauguration, the AIMR has generated
many promising results. And weplan to further reinforce our global
network with joint centers andpartner institutions, with the goalof forming a global community forpromoting collaboration between
mathematics and materials science.
I would like to take this opportunity
to thank you for your interest andhope that this publication will spark
many more initiatives.
Motoko Kotani
Director
AIMR

Tohoku University’s Advanced Institute for Materials Research (AIMR)
promotes fusion research in materials science across disciplinary barriers

The AIMR is leading the world in facilitating collaboration between materials science and mathematics. In
an environment where more than half of the researchers come from abroad, scientists at the AIMR
— young and international included — contribute to discussions and joint research projects, enabling the
AIMR to achieve world-leading research results.
AIMResearch’s website introduces cutting-edge research from the AIMR through research highlights,
spotlights, news and job vacancies. Access AIMResearch online now!

research.wpi-aimr.tohoku.ac.jp
Latest research highlights• Microscopy: Ultrasharp probing of solar cells• Electrochemistry: Mapping a battery electrode• Graphene: Customized from the bottom up• Biosensors: A gentler route to hydrocarbon electrodes• Polymers: Nanoscale nudges reveal critical clues

RESEARCH HIGHLIGHTS
The AIMR advances research in bulk metallic glasses, materials
physics, soft materials and devices/systems, and actively promotes collaboration among these divisions toward the development of groundbreaking technologies that cross the boundaries
of conventional fields of study — bridging the disciplines ofmaterials science, physics, chemistry and precision, mechanical,
electronics and information engineering. The Mathematics Unit
further complements the AIMR’s research activities.

RESEARCH HIGHLIGHTS

Tissue engineering

Strong hydrogel carries current

Cultured cells can form functional,
three-dimensional tissue if given a
suitable scaffold to guide their growth.
Biocompatible hydrogels — which contain mostly water — provide useful scaffolds for some cell types. However, theusual method of stiffening hydrogels by
reducing their water content can impede
cell growth. In addition, hydrogels do
not typically conduct electricity, making
them unsuitable for cells that require
electrical stimulation to grow.
Samad Ahadian and colleagues fromthe AIMR at Tohoku University have
now used carbon nanotubes to create ahydrogel that is both sturdy and a good
conductor of electricity1. The additionof nanotubes presents an alternative
way to tune both the mechanical andelectrical properties of hydrogels, theresearchers say.
Using a gelatin methacrylate hydrogel as a base, the researchers added
multi-walled carbon nanotubes — thinstraws of carbon atoms measuring
40–90 nanometers in diameter — todouble the hydrogel’s stiffness.
Initially, the nanotubes were randomly
oriented in the gel, but the researchers
were able to align them by applying anelectric field. Next, they used a burst ofultraviolet light to form bonds between
the gelatin methacrylate molecules, fixing the nanotubes in place. The nanotube
network enabled the gel to carry between
100 and 1,000 times more current thanthe unaligned nanotubes, depending on
the nanotube concentration.
The researchers then tested theirhydrogel as a growth medium for
C2C12 mouse muscle myoblasts, a typeof muscle cell that can fuse together toform myotubes. The myotubes in turn6

© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Supporting a hydrogel with a carbon-nanotube network helps to grow muscle tissue
for medical applications

50 μm
Myoblasts (green) can fuse to form functional muscle fibers after aligning in grooves within a carbonnanotube-supported hydrogel. Cell nuclei are stained in blue.

mature into myofibers, which behave
like normal muscle tissue.
More than 95 per cent of the myoblasts
seeded into the nanotube-laden gel
survived. Additionally, after three daysin culture the growth of the cells accelerated thanks to the greater number ofanchoring sites offered by the nanotubes.
By creating a groove in the hydrogel,the researchers were able to encourage
myoblasts to line up end-to-end, helping them to form healthy myotubes
that could contract properly. After eightdays in culture, the researchers applieda small voltage that promoted muscle
cell differentiation along the groove— an effect that was most pronounced
in the aligned-nanotube hydrogel(see image).

Hydrogel-grown muscle tissue has
numerous potential medical applications.
“Engineered muscle tissues can be used as
an efficient platform to investigate drugcandidates to treat diabetes,” explains
Ahadian. “Such tissues can be made usinga patient’s own muscle cells, which could
be a major step toward personalized
medicine and would make it possible toeliminate expensive and time-consuming
animal experiments for drug screening.”
1. Ramón-Azcón, J., Ahadian, S., Estili, M., Liang, X.,
Ostrovidov, S., Kaji, H., Shiku, H., Ramalingam, M.,
Nakajima, K., Sakka, Y. et al. Dielectrophoreticallyaligned carbon nanotubes to control electricaland mechanical properties of hydrogels
to fabricate contractile muscle myofibers.
Advanced Materials 25, 4028–4034 (2013).

AIMResearch 2014

RESEARCH HIGHLIGHTS

Solar cells

The benefits of separation

The plastic materials used in organic
solar cells are abundant and cheap,
making such devices promising for
harvesting solar energy. The complexityof the organic molecules used in thesecells, however, has prevented a full understanding of the mechanism by which
they convert sunlight into electricalcharge. This complexity has also hampered their use in practical applications.
Hiroyuki Tamura and Irene Burghardt
from the AIMR at Tohoku University
and the Goethe University Frankfurt,
Germany, respectively, have now shownhow the distribution of electrons acrossan organic solar cell plays a crucial rolein generating electricity1.
Organic solar cells are typicallycomprised of a mixture of polymer
molecules and cage-like spherical ballsof carbon known as ‘buckyballs’. Light
incident at the interface between thesemolecules excites the electrons present
in the molecules. As the electrons moveacross the molecules, they leave behind
empty spaces — ‘holes’ — which are also
mobile. The role of the buckyballs is totransport the electrons away to the contact electrode while the polymers carrythe corresponding holes (see image).
A crucial aspect for the operationof an organic solar cell is the initialcharge separation of electrons from thepolymer into the buckyballs. “A fastercharge separation leads to a more efficient operation of the solar cell as it
minimizes the opportunity for electricallosses,” explains Tamura. However, thesize and complexity of the organic molecules involved has impeded a deeper
understanding of this process.
To investigate the charge-transfer
mechanism, Tamura and Burghardt

AIMResearch 2014

-

-

+

Modified, with permission, from Ref. 1 © 2013 American Chemical Society

A better understanding of how electrical charges separate in organic solar cells is
helping to improve energy harvesting+

Organic solar cell comprising buckyballs (left) and chains of polymer molecules (right). The separationof electrons (minus sign) and holes (plus sign) to opposite contacts of the cell is crucial for the efficientperformance of the cell.

used powerful quantum dynamical
simulations that were able to computethe properties of large systems. Theirresults reveal that the charge transfer
is not initiated by the simple ‘hopping’process of electrons from the polymers
to the buckyballs.
Rather, the charge transfer relieson the fact that in quantum physics
each electron can also be described asa wave, which is spread out in space.
When an electron is excited by sunlight, its wavefunction expands. This
expansion lowers the energy barrier forthe charge-transfer process to occur,thus enabling the electrons to moveto the buckyballs. “Unlike hopping

processes, this scheme can explain theefficient, ultrafast charge-separation
observed in some experiments,” explains Tamura.
The new mechanism will be important
for the design of enhanced organic solar
cells. For example, adds Tamura, “thereduced energy barrier will allow solar
cell designs that enable the absorptionof a broader cross-section of sunlight,
especially at longer wavelengths.”
1. Tamura, H. & Burghardt, I. Ultrafast charge
separation in organic photovoltaics enhanced
by charge delocalization and vibronically hot
exciton dissociation. Journal of the American
Chemical Society 135, 16364−16367 (2013).

7

RESEARCH HIGHLIGHTS

Biomaterials

Carpeting the way for lessinvasive treatments
Tissue engineering is expected to offer
innovative regenerative approaches
for cell organization and delivery
in the body. A research team led by
Toshinori Fujie and Ali Khademhosseinifrom the AIMR at Tohoku University has
now developed ultrathin polymer sheets— ‘nanosheets’ — that support cell growth
and transplantation at a specific location1.
Fujie says that the team’s nanosheets
were inspired by the classical fairy tale
“The Arabian Nights”, in which a flying carpet delivers multiple people todesirable places. To manufacture thenanosheets, the team deposited thebiodegradable polymer poly(lactic-coglycolic) acid, together with magnetic
nanoparticles to aid manipulation of
the nanosheets, on a microscopic stamp.
The researchers then transferred themicropatterned layer onto a glass surface
pre-coated with a sacrificial polymer
that, when dissolved in water, releases
the nanosheet from the surface.
Fujie and Khademhosseini’s teamevaluated the potential for using theirnanosheets to treat age-related maculardegeneration — a common disease that
leads to loss of sight and eventual blindness. Treatment of this disease hinges on
repairing the damaged retinal pigment
epithelium (RPE) layer of the eye, whichis sandwiched between the retinal photoreceptors and the vascular network.
Using a syringe to transplant RPE
cells at the degeneration site provides anattractive way to restore this damaged
monolayer — the alternative approachis surgical intervention, which carries ahigh risk of infection. Materials scientists
have already created several natural andartificial supports for delivery of the cells
but their size exceeds that of the narrow8© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Ultrathin polymer-based sheets aid tissue repair by providing a new platform fortargeted cell transplantation

Monolayer of retinal pigment epithelium cells (green) on a polymer nanosheet (red).

subretinal space. Furthermore, the low
flexibility of such supports hinders their
aspiration and injection through a syringe.
In vitro assessments showed that RPE
cells adhered to the team’s nanosheets
and self-assembled into a densely
packed, cobblestone-like monolayer(see image). Moreover, the magnetic
particles also enhanced the surface
roughness of the nanosheets, thereby
promoting cell migration and proliferation — a further advantage for RPE
monolayer transplantation. When compressed in a syringe needle, the RPEbearing nanosheets retained viable cells,
whereas thicker sheets preserved only
a few cells of mostly low viability. The
nanosheets also recovered their original
shape without distortion.

When injected into the subretinal spaceof a swine eye ex vivo, the nanosheets
properly spread and attached to the macula. The RPE monolayer also retained its
cellular activity during the procedure.
The researchers are currently investigating ways to utilize their nanosheets
as scaffolds for stem cells and drug molecules. “The controlled release of drugs
and growth factors from the nanosheets
may enhance the tissue integration of thetransplanted cells,” says Fujie.
1. Fujie, T., Mori, Y., Ito, S., Nishizawa, M., Bae,
H., Nagai, N., Onami, H., Abe, T., Khademhosseini, A. & Kaji, H. Micropatterned polymericnanosheets for local delivery of an engineered
epithelial monolayer. Advanced Materials 26,
1699–1705 (2014).

AIMResearch 2014

RESEARCH HIGHLIGHTS

Bioimaging

A sharper view of teeth

Over the course of its lifetime, a typicalshark will lose and regrow thousands ofteeth as they become embedded in preyor worn out. None of these teeth, however, ever suffers from cavities. Recent
studies have discovered that the hard,enamel-like coating of a shark tooth ismade from fluorapatite — a fluorinatedcalcium phosphate material that is anactive ingredient in most toothpastes.
Although researchers already attributehigh concentrations of fluoride ions to
low levels of tooth decay, direct evidenceof this chemical’s cavity-reducing action
remained elusive.
Chunlin Chen and colleagues fromthe AIMR at Tohoku University, in collaboration with researchers from acrossJapan, have now used transmission
electron microscopy (TEM) to capture
the first images of individual atoms
inside shark teeth1. Their findings showthat unusual bonding interactions between fluorine and calcium atoms may
be critical to understanding fluorine’s
tooth-strengthening capabilities.
For decades, scientists have used TEM
to observe the atomic-scale structureof inorganic materials. Shark teeth,
however, are biominerals — complex
substances containing both delicate
organic matter and robust inorganic
minerals, which are easily damaged byhigh-energy electron beams. Current
understanding of the enamel-like structures that envelop shark teeth is thus
limited to micrometer-sized regions.
To overcome this challenge, the researchers used a scanning transmission
electron microscope equipped withspecial ‘aberration-corrected’ lenses andlow-dose imaging capabilities. The approach employs a small lens aperture that

AIMResearch 2014

© 2014 Chunlin Chen

The first atom-resolved images of biominerals in shark teeth reveal important
insights into fluorine’s cavity-fighting power

Direct atomic imaging inside the enamel-like coating of a shark tooth shows that fluorine atoms (bluespheres) play a critical role in stabilizing tooth enamel.

disperses the electron beam over a wider
area than usual, thereby lowering thebeam intensity. However, because sucha low-dose beam results in noisy TEM
images, the researchers had to search fora careful balance between irradiationinduced damage and image quality.
When the team examined a toothfrom an Isurus oxyrinchus — also known
as a shortfin mako shark — TEM images
showed that its enamel-like structure
contained bundles of single-crystalline
fluorapatite nanorods, roughly fifty
nanometers wide. Deeper probing revealed a hexagonal atomic frameworkinside the nanorods, with calcium,
phosphorus and oxygen surrounding acentral fluorine atom (see image). This
structure suggests that fluorine is critically important to shark tooth enamel

as its loss would destabilize the entire
chemical structure.
Computer simulations of the structure of fluorapatite further illustrated
fluorine’s unique role in dental health.
The researchers were able to determinethat bonding between fluorine and calcium contained both ionic and covalent
contributions, making it stronger thantypical fluorine bonds. “The direct imaging of fluorine atoms and its surprising
mixed covalent–ionic bonding should beof fundamental significance to the fieldof dentistry,” says Chen.
1. Chen, C., Wang, Z., Saito, M., Tohei, T., Takano, Y.
& Ikuhara, Y. Fluorine in shark teeth: Its direct
atomic-resolution imaging and strengthening
function. Angewandte Chemie International
Edition 53, 1543–1547 (2014).

9

RESEARCH HIGHLIGHTS

Catalysis

Pinning down degradation

Nanoporous gold has a crucial role as acatalyst in the production and processing of commodity chemicals underenvironment-friendly conditions. Its
tiny pores provide exceptional activity
in reactions that involve oxygen, suchas the thermodynamically challenging
transformation of carbon monoxide(CO) into carbon dioxide. However, themechanism that governs its degradationand loss of activity during catalysis has
so far remained elusive.
By using sophisticated microscopy
techniques to monitor changes in the
structure of nanoporous gold during COoxidation, a team led by Takeshi Fujita
from the AIMR at Tohoku University
has gained unprecedented experimental insight into the catalysis-induced
degradation mechanism at the atomic
scale1. Their work has also revealed thesignificance of planar defects — and inparticular the formation of twin boundaries — in averting this process, thereby
offering new avenues for enhancing
catalytic activity and stability.
The researchers first synthesized
freestanding nanoporous gold leaves
through a dealloying process, in which
nitric acid removes the silver from anultrathin gold–silver sheet. The resulting
gold structure comprised nanopores
embedded in flat, close-packed ‘terraces’
separated by single-atom ‘steps’.
The nanoporous gold catalyst did notexhibit any noticeable change underelectron beam irradiation in pure COor oxygen environments or undervacuum, indicating its stability. Upon
exposure to a CO–air gas mixture, thenanopores and connecting material
expanded with increasing reaction time,
which was associated with a reduction

10

CO + O2

CO2

Nanoporous
gold

2 nm

Gold atoms migrate at right angles (red arrow) to a planar ‘twin’ interface (yellow lines) during the oxidationof carbon monoxide on nanoporous gold.

in catalytic activity. Furthermore, silver
and gold in the connecting material
were initially uniformly distributed but
gradually became separated as thereaction progressed.
To gain insight into this coarsening
mechanism, Fujita and colleagues usedan environmental transmission electron
microscope to obtain high-resolution
images of individual nanopores under reaction conditions. When they increased
the reaction time, the nearly roundnanopores became faceted and widened
before merging with neighboring pores.
The researchers found that thecoarsening relied on the rapid oxidationinduced migration of gold atoms on
the single-atom reactive steps of theuppermost terrace (see image). The
nanopores grew fastest perpendicular to

the twin interfaces — a clear indicationof the importance of these defects. In theabsence of twin defects, the nanopores
did not display any preference in growth
direction. “Twin planes can effectively
pin the gold atoms to the surface, eventually suppressing nanopore coarsening,”
explains Fujita.
The team is currently evaluating ways
to boost catalyst performance and longevity by augmenting the density of planar
defects in nanoporous gold. “We are also
trying to develop new exhaust gas catalysts based on this system,” adds Fujita.
1. Fujita, T., Tokunaga, T., Zhang, L., Li, D., Chen, L.,
Arai, S., Yamamoto, Y., Hirata, A., Tanaka, N., Ding,
Y. & Chen, M. Atomic observation of catalysisinduced nanopore coarsening of nanoporous
gold. Nano Letters 14, 1172–1177 (2014).

AIMResearch 2014

Foreground: Modified from Ref. 1 © 2014 American Chemical Society; background: © 2014 Takeshi Fujita

Atomic-scale examination of nanoporous gold demonstrates that surface defects
suppress catalyst degradation during carbon monoxide oxidation

RESEARCH HIGHLIGHTS

Materials

Polymer chains singled out
Colorless single-polymer chains can be made from colorful dye monomers held
rigid inside a molecular crystal

AIMResearch 2014

Visible light© 2014 Yonghao Zheng

Single crystals of polymers can be difficult to obtain because their long andflexible backbones tend to get tangled,
forming structures with no long-rangeorder. However, the process of preparing these polymers is eased if polymerization takes place inside a molecular
crystal in which the reactive monomers
are pre-organized in a position that
almost corresponds with the repeat
distance of the desired polymer. The
confinement of these monomers during polymerization yields long singlepolymer chains.
Researchers from the AIMR at
Tohoku University and the Universityof California have used this approachto synthesize a new class of polymers1.
They constructed two new polymers
from bis(indenedione) monomers,
which are highly colored conjugatedorganic dyes.
Polymerization ordinarily requires
heat, ultraviolet light or pressure. In
contrast, the researchers used visible
light to induce the reactions between
the monomers and produce the newpolymers (see image). “This is the firsttime that the quantitative conversion ofa small molecule to a macromoleculehas been achieved with visible light,”
says Yonghao Zheng, a member of theresearch team.
Unlike the monomers they wereconstructed from, the polymer strands
are colorless because polymerization
breaks the monomers’ conjugation. The
progress of the reaction can therefore beseen with the naked eye. The researchers shone light on the molecular crystal,causing the top layer of the crystal topolymerize and become transparent.
Light can then pass through to the

Heat
Visible light causes the monomers in the molecular crystal (green) to polymerize, a reaction that can bereversed by heating.

next layer, which subsequently undergoes polymerization. This continues
until the entire crystal is colorless.
The researchers were able to isolate
individual polymer strands by applying
and then removing sticky tape from thepolymerized crystal.
The resulting polymers are strong,
explains Zheng. “One possible application is as a strengthening component
in composite materials.” The polymers
lose their translucency when heat is
applied, breaking them down to theircomponent parts, which allows any
weaknesses to be spotted.
The researchers also showed thatsingle chains of the two polymers could
be made inside molecular crystals dissolved in highly concentrated solutions,as well as on semicrystalline thin films.

These synthetic methods are well-suited
to manufacturing, thereby opening up
this class of polymers to a wide range ofapplications. “The feature of polymerization on thin films is of great potential
for solution-processing applications inorganic electronics, such as thin-film
transistors,” says Zheng.
The researchers now plan to focus
on unfolding the fundamental properties of single chains of polymers
and are currently studying theirmechanical properties.
1. Dou, L., Zheng, Y., Shen, X., Wu, G., Fields, K.,
Hsu, W.-C., Zhou, H., Yang, Y. & Wudl, F. Singlecrystal linear polymers through visible
light–triggered topochemical quantitative
polymerization. Science 343,
272–277 (2014).

11

RESEARCH HIGHLIGHTS

Oxide interfaces

Blueprint for a super-material
Atomic-scale images expose the secret mechanisms that turn insulating oxide films
into electrically and magnetically active interfaces

12

High

Low

Modified, with permission, from Ref. 1 © 2014 American Chemical Society

Metal oxides play many important roles
across a variety of high-tech energy
applications, such as photovoltaic cells
and lithium-ion batteries. Recently,
scientists discovered that the electronic
properties of extremely thin metal oxide
films are unlike those of any other material. Developing metal oxide thin films
into practical devices requires atomiclevel knowledge of their structures andproperties. Unfortunately, the complex
chemical arrangement of such films
makes them difficult to characterize
using standard techniques.
Takeo Ohsawa, Taro Hitosugi andcolleagues from the AIMR at Tohoku
University have now used scanningtunneling microscopy to visualize
atoms inside metal oxide thin films1.
This approach provided the researcherswith unprecedented surface images ofstrontium titanate (SrTiO3) — an insulating metal oxide that transforms into a
two-dimensional conductor, a magnet oreven a superconductor when interfacedwith lanthanum aluminate (LaAlO3).
According to Ohsawa, many aspectsof this LaAlO3/SrTiO3 system arecontroversial — particularly a phenomenon known as the ‘termination layer’problem. SrTiO3 is made of alternating
sheets of titanium dioxide (TiO2) andstrontium oxide (SrO), which means thatit exhibits contrasting effects, dependingon which layer is in contact with LaAlO3.
Films terminating with TiO2 become
two-dimensional conductors, whereas
those terminating with SrO retain theirinsulating properties.
To investigate this problem, theresearchers combined a low-temperaturescanning tunneling microscope witha laser-driven, thin-film deposition

3 nm
Scanning tunneling microscopy images of strontium oxide (SrOx) islands (red, top) after deposition of SrO on atitanium–oxygen surface (bottom).

system. This allowed them to observe
the early stages of SrO film growth — acritical period during the establishmentof a new material. First, they prepared
an ultra-clean SrTiO3 surface terminatedby a periodically arranged layer of titanium and oxygen atoms. Then they used
the scanning tunneling microscope tomonitor how the surface changed as apulsed laser slowly deposited increasing
amounts of SrO.
Instead of forming crystalline structures, the SrO atoms clumped together
into random, ‘island’-type arrangements(SrOx) that disrupted the periodicity of
the underlying titanium–oxygen layer(see image). Careful comparisons of preand post-deposition surfaces revealed
that titanium atoms merged with the
SrOx islands during this growth phase,thus forming an atomic mixture that candisrupt interfacial electron transport.
“These results indicate the possibility of titanium atom incorporation into
LaAlO3 films when they are deposited on
SrO-terminated SrTiO3 substrates, which
may lead to the suppression of twodimensional conductivity in this system,”says Ohsawa. The researchers say that theneed to account for excess titanium at
the LaAlO3/SrTiO3 interface should help
to solve the termination layer problem,
while also giving researchers a blueprint
for developing atom-by-atom engineeredoxides with exotic electronic properties.
1. Ohsawa, T., Shimizu, R., Iwaya, K. & Hitosugi, T.
Visualizing atomistic formation process of SrOx
thin films on SrTiO3. ACS Nano 8,
2223–2229 (2014).

AIMResearch 2014

RESEARCH HIGHLIGHTS

Material defects

Down to the core

Crystal dislocations play a crucial role indefining the physicochemical propertiesof many materials. These linear defects,
although capable of causing structural
failure in semiconductor-based devices,
contribute significantly to the plastic
behavior of metals and alloys. However,the core structures of such defects remain poorly understood.
A team of researchers led by
Yuichi Ikuhara from the AIMR at
Tohoku University have now uncovered
the structures of dislocation cores at
the atomic scale1. “Different dislocation cores can have a vastly different
impact on the properties of real materials,” explains Zhongchang Wang.
The researchers investigated thesestructures by combining complex
simulations of atoms with systematic,
high-resolution imaging.
Existing attempts to characterize
dislocation cores have relied on either
diffraction or scanning transmission electron microscopy (STEM).
Diffraction provides only averaged
structural information and is thus unable to detect individual defects. STEM,
on the other hand, enables atomic resolution imaging but is limited to just a few
dislocations. “Unless the total numberof dislocation types in the material is
known, we can only observe a selectionof individual defects in the sea of dislocations in a real material,” says Wang.
Using a computational–experimental
approach, the researchers determined
the geometrical arrangements of all
dislocation core structures for eachdislocation type. First, they generated bicrystals from magnesium oxide(MgO), an ionic material that exhibits
dislocation-dependent properties. Then,

AIMResearch 2014

© 2014 Zhonchang Wang and Yuichi Ikuhara

Crystal defect cores adopt multiple arrangements in real materials

The atomic arrangement at the [100] dislocation of magnesium oxide. This arrangement differs from that in
the bulk, which may result in dramatically different material properties.

they joined two identical MgO crystals
at a slight angle to create one-dimensional edge dislocations. An extensive
computational search provided optimal
dislocation structures, which the researchers then compared with electron
microscopy images.
The team’s investigations showedthat only one stable structure exists
for the [110] dislocation of MgO — afinding that is consistent with previous
observations. Atom-resolved STEM
imaging gave the same core structure
as the computed geometry for thisdislocation, thus validating the researchers’ approach. Further simulations
revealed three core arrangements withsimilar energies for the [100] dislocation(see image), which matched the electron
microscopy images.

“Impurities preferably segregate at[100] dislocations instead of at [110]dislocations in MgO, which may explain
why the presence of [100] dislocations damages the intrinsic insulating
properties of MgO whereas the [110]dislocation is not detrimental to MgOelectronic devices,” explains Wang.
“We are now applying this technique toinvestigate dislocation core structuresin other materials, such as TiO2,” says
Ikuhara. In addition, the researchers arealso planning to determine the differences between cores by measuring theproperties of individual dislocations.
1. Wang, Z., Saito, M., McKenna K. P. & Ikuhara, Y.
Polymorphism of dislocation core structures at
the atomic scale. Nature Communications 5,3239 (2014).

13

RESEARCH HIGHLIGHTS

Nanomaterials

Tiny flakes with a brilliant future
Newly discovered atomic sheets could outshine graphene inphotosensitive detectors

14

Light
Dra

in
Modified, with permission, from Ref. 1 © 2014 American Chemical Society

Graphene — an ultrathin material consisting of a single layer of carbon
atoms — has the potential to revolutionize electronic devices by making themsmaller, faster and more efficient. One
limitation of graphene, however, is that it
can absorb only a small fraction of visible
light. This prevents it from being used inphotodetectors — optoelectronic components critical to the operation of solar cells
and digital cameras.
Katsumi Tanigaki and colleagues fromthe AIMR at Tohoku University have now
discovered a novel nanostructured material — gallium telluride (GaTe) flakes —that can detect light signals with a higher
sensitivity and a faster electrical responsethan any existing two-dimensional (2D)
layered material1.
Although electrons can move throughthe hexagonally bonded framework ofgraphene at extraordinary speeds, graphene’s ‘indirect’ optical bandgap meansthat any interaction with light must proceed via a time- and energy-consuming
detour involving intermediate states.
‘Direct’ bandgap materials, in contrast,
can absorb large quantities of photons byimmediately converting them into a photoelectric current, making such materials
extremely photosensitive.
The researchers’ extensive search fora direct-bandgap material that is atomically thin led them to GaTe crystals. This
material’s unique structure — 2D sheetsof Te–Ga–Ga–Te atoms (see image)stacked into weakly bonded, multilayered
complexes — provides it with intriguing
optoelectronic properties. Furthermore,
GaTe is lightweight and easy to synthesize.
But when the researchers began
their investigation, they encountered a
crucial problem: the bandgap of GaTe

Sou

rce

Gate
SiO2

A novel sensor based on two-dimensional gallium telluride (GaTe) sheets is extremely sensitive to light signals.

changes from being direct to indirect
when its bulk crystal structure is thinned
down to a monolayer. Through collaboration with theoreticians from theUnited Kingdom to better understandthe optical properties of this system, theteam came to realize that finite, ten-layer
GaTe stacks could yield the improved
conductivity of 2D systems while retaining a direct bandgap.
To achieve this goal, the researchers resorted to a low-tech but effective method:using sticky Scotch tape to strip off verythin flakes from bulk GaTe crystals. This
technique — pioneered for isolating
single-layer graphene — produced thedesired multilayered GaTe flakes, which
they then transferred to a silicon device.
Experiments showed that the tiny flakes

could respond to a wide range of lightwithin milliseconds. Importantly, thenanomaterials produced a photocurrentof light-generated electrons several ordersof magnitude higher than that generated
by graphene.
“A direct bandgap is very important forachieving both a high sensitivity and a fast
response time in a photodetector,” says
Tanigaki. “The intrinsic direct bandgap
available from GaTe nanoflakes makes
them a promising candidate for future
photodetectors beyond graphene.”
1. Liu, F., Shimotani, H., Shang, H.,
Kanagasekaran, T., Zólyomi, V., Drummond, N.,
Fal’ko, V. I. & Tanigaki, K. High-sensitivity photodetectors based on multilayer GaTe flakes. ACS
Nano 8, 752–760 (2014).

AIMResearch 2014

RESEARCH HIGHLIGHTS

Nanodevices

Molecular motor powers shuttle
Kinesin protein ferries microtubules along nanotube track

AIMResearch 2014

Microtubule

Kinesin
Reproduced, with permission, from Ref. 1 © 2014 American Chemical Society

Miniature chemical reactors, known as
lab-on-a-chip devices, are increasingly
being used to analyze biological samples.
Unfortunately, the bulky pumps and batteries needed to operate such devices limit
their further miniaturization and prevent
them from being directly implanted into
the body for monitoring applications.
Winfried Teizer from the AIMR at
Tohoku University and colleagues have
now developed a much smaller systemthat uses a biological motor to transportcargo along a track made of carbon nanotubes (see image)1.
Kinesin-1 is a natural motor protein that is powered by adenosine
triphosphate (ATP), the principal energycarrying molecule in cells. Kinesin uses
this energy to carry cell components along
hollow cylinders called microtubules,
which consist of polymers of tubulin
proteins and are typically 25 nanometers
wide and several micrometers long.
Teizer’s team reversed this arrangementby anchoring kinesin proteins along a
track, and then using them to propel
microtubules like a conveyor belt.
The researchers coated a glass platewith aminosilane molecules and attachedthem to polyethylene glycol chains tippedwith a biological compound called biotin.
They then added multiwalled carbon
nanotubes (MWCNTs) that were peppered with streptavidin, a protein thatbinds strongly to biotin. The streptavidin
molecules covered the nanotube surface
with a density of around 35,000 per
square micrometer.
The scientists used electrodes that were
crenellated into a saw-tooth pattern tosubject the nanotubes to an electric field.
This process, called dielectrophoresis,
neatly aligned the nanotubes so that they

Carbon nanotubes

Polyethylene
glycol chain

Glass
Multiwalled carbon nanotubes attached to a glass plate act as a track for a kinesin-powered microtubule
conveyor belt.

formed tracks between the electrodes.
The researchers covered the nanotubes
with kinesin bearing a biotin linker, andthen added microtubules that had beenlabeled with a fluorescent dye calledrhodamine. As the kinesin molecules consumed ATP, they forced the microtubules
to glide along the track at an average speedof around 150 nanometers per second.
This is slower than kinesin’s usual velocity
of about 800 nanometers per second. The
researchers suggest this may be because
their kinesin was engineered to be shorter
than natural kinesin, limiting its ability to
twist as it propels the microtubules.
“We have demonstrated that gliding on
MWCNTs is possible, but we don’t know
if the microtubule shuttle can transit

between tracks, which would allow thepossibility of a complete circuit basedon MWCNTs,” says Teizer. “We are now
investigating microtubule displacement
between MWCNT segments.”
The researchers hope that theirmicrotubule conveyor belt could eventually be loaded with cargos such as
viruses, drugs, proteins or nanoparticles,
which would be useful for a variety ofbiosensing applications.
1. Sikora, A., Ramoń-Azcoń, J., Kim, K., Reaves,K., Nakazawa, H., Umetsu, M., Kumagai, H.,
Adschiri, T., Shiku, H. & Matsue, T. et al. Molecularmotor-powered shuttles along multi-walledcarbon nanotube tracks. Nano Letters 14,
876–881 (2014).

15

RESEARCH HIGHLIGHTS

Nanoparticles

Stretching water droplets

Droplets of water suspended in oil are
spherical because this shape minimizes
the contact area between these two
immiscible liquids. Researchers fromthe AIMR at Tohoku University andthe University of Massachusetts in the
United States have now used nanoparticles to modify the shape of liquiddrops suspended inside another liquid1.
The drops retain their modified shapes
for long periods of time. “This is thefirst demonstration of stable, long-lived,
non-equilibrium shapes of one fluid
inside another,” explains team leader
Thomas Russell.
The researchers added the nanoparticles to a dispersion of water and anamine-ended polymer in oil. The polymers initially congregated at the interface
between the oil and water. The nanoparticles then diffused from the aqueous phaseto the interface, where they interactedwith the amine groups of the polymer
to form nanoparticle surfactants. These
grouped together to minimize the surface
tension at the interface.
Next, the researchers placed the system between two electrodes and applied
an electric field. Electrostatic forcesinduced by the electric field caused
the drops to deform and elongate into
ellipsoids (see image). The surface areaof each drop increased substantiallywhile the drop volume remained constant, thus allowing more nanoparticle
surfactants to form at the interface.
The extent to which the drops elongate
depends on the strength of the applied
electric field. When the researchers turned
the electric field off, each drop tried toreturn to its original spherical shape.
Although the drops did relax slightly, any
significant decrease in surface area was

16

5 μm

Spherical water drops suspended in oil and coated in nanoparticle surfactants can be stretched into ellipticalshapes by applying an electric field.

prevented by the nanoparticle surfactants
being grouped together at the interface.
The team investigated a series of different
groupings by changing the direction of
the electric field, thereby creating a rangeof shapes. They also deformed the dropsby stirring, thus forming tubules of waterin the oil phase.
The drops retained their nonspherical shapes for at least a month.
“Eventually the liquid within the droplet diffuses into the outer liquid andevaporates, causing the nanoparticle
assembly to wrinkle,” explains Russell.
In their wrinkled form, the droplets
resemble raisins in appearance.

This work could help realize the
dream of all-liquid batteries. “If one
liquid is an insulating oil and thesecond is aqueous based, we cantransport charge quickly within the
aqueous phase from one side of a container to another,” says Russell. “Thisis precisely what is needed for battery
applications; our work presents a routeby which an all-liquid battery could
be produced.”
1. Cui, M., Emrick, T. & Russell, T. P. Stabilizing
liquid drops in nonequilibrium shapes by theinterfacial jamming of nanoparticles. Science
342, 460–463 (2013).

AIMResearch 2014

Reproduced from Ref. 1 © 2013 M. Cui et al.

Water droplets suspended within oil have been pulled into stable, elongated shapes

RESEARCH HIGHLIGHTS

Spintronics

Tuning materials for improved
memory performance
Today’s magnetic storage media tend
to orient their bits vertically — thatis, perpendicular to the thin films thatcarry them. This arrangement, known
as perpendicular magnetic anisotropy,
has several advantages over older techniques: it not only lowers the electricalcurrent needed to switch the directionof the bit (and therefore to write information) but also makes the bit more
thermally stable.
However, there are some difficulties in using perpendicular magnetic
anisotropy. One is the relative difficultyof controlling the magnetic interaction
between adjacent films, which is necessary for emerging technologies likespin valves and all-optical data storage.
In particular, an antiferromagnetic
arrangement, in which the magnetic
dipoles of adjacent films point in opposite directions, is difficult to achieve.
Now, Qinli Ma and co-workers in the
Mizukami Laboratory at the AIMR at
Tohoku University have demonstrated a
new way of controlling the interaction
between adjacent magnetic layers thatallows the creation of ferromagnetic or
antiferromagnetic arrangements at will1.
The researchers fabricated an interface between two magnetic thinfilms — one made from manganese andgallium and the other made from ironand cobalt — in which the magnetic bits
were defined perpendicular to the films’
plane (see image). As they increased
the cobalt content of the iron–cobalt
film beyond 25 per cent, the interface
between the films abruptly switchedfrom ferromagnetic (with aligned dipoles) to antiferromagnetic.
Ma and co-workers say that this unusual behavior results from the energy

AIMResearch 2014

© 2014 Qinli Ma

Material composition tuning is moving magnetic tunnel junctions closer to reality

At low cobalt concentrations (left), the spin in the iron–cobalt film (red arrow) is aligned with the spin in
the manganese–gallium film (green arrow) by ferromagnetic exchange interaction at the interface (redsheet). As the cobalt content is increased (right), the iron–cobalt film spin flips to oppose the spin in the
manganese–gallium film by antiferromagnetic exchange interaction at the interface (blue sheet).

structure of their two films. The behaviorof the film interface is dominated by thehighest-energy electrons in each film.
Increasing the cobalt content adds electrons to the iron–cobalt film, thus raising
the energy of the highest-energy electrons at the interface. Because the number of available electron states that alignantiferromagnetically is greater at higher
energies, the film interface switchesfrom ferromagnetic to antiferromagnetic
when enough cobalt is added.
Using variations in the density ofstates to tune the behavior of an interface may prove to be an important new
tool in engineering thin-film magnetic
systems, says Ma. It also improves theprospects for the use of manganese–
gallium films in applications likemagnetic random-access memory. In
fact, when the researchers used theirpair of films to build a memory device
called a magnetic tunnel junction, thedevice performed unusually well. They
were able to vary the device’s resistanceby 60 per cent at room temperatureusing magnetic fields alone and by 120
per cent at low temperature, suggesting that practical devices may not be
far off.
1. Ma, Q. L., Mizukami, S., Kubota, T., Zhang, X. M.,
Ando, Y. & Miyazaki, T. Abrupt transition
from ferromagnetic to antiferromagnetic
of interfacial exchange in perpendicularly
magnetized L10-MnGa/FeCo tuned by Fermi
level position. Physical Review Letters 112,
157202 (2014).

17

RESEARCH HIGHLIGHTS

Nanomaterials

Graphene grows up

The perfect, honeycomb-like bonding
inside a sheet of graphene allows charge
carriers to move through the material as‘massless’ particles called Dirac fermions.
This phenomenon gives graphene intrinsically higher electron mobility thanany other known material — a featurethat promises to usher in an age ofultrafast and inexpensive carbon-based
electronics. However, the atom-scalethinness that makes graphene so valuable also makes it difficult to manipulate
into practical devices.
Yoshikazu Ito, Mingwei Chen andcolleagues from the AIMR at Tohoku
University have now discovered a way to
produce three-dimensional (3D) nanoporous graphene structures that preserve
the massless Dirac fermions — and thus
the astonishing electron mobility — of
two-dimensional (2D) systems1.
Turning graphene sheets into complex
3D networks is no easy task. A recently
developed method, known as templateassisted growth, uses removable substrates
to force carbon atoms into unconventional arrangements. This technique has
successfully produced 3D graphene withintriguing mechanical and chemical
properties. Yet the electrons inside thesematerials cannot travel efficiently because
most templates have discontinuous orrough surfaces that introduce critical
defects into the 3D framework.
The researchers developed an improved template with a ‘bicontinuous’
structure containing a smooth, hard surface of nickel atoms and nanoscale pores.
Then, by carefully heating this templatein a chemical vapor deposition (CVD)chamber filled with hydrogen, argon andbenzene gases, they grew uniform films
of graphene all over the nickel template.

18© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

An innovative synthesis technique generates three-dimensional nanoporousgraphene structures with high-speed electronic transport capabilities

10 μm
A scanning electron microscopy image of three-dimensional nanoporous graphene, a new low-cost material
with extraordinary electronic properties.

Finally, they used acid to remove thenickel, yielding a freestanding, bicontinuous 3D structure of graphene with
nanopores (see image).
Experiments revealed that the presence of the 3D nanopores, which theresearchers could tailor by controllingthe duration and temperature of the
CVD process, had an enormous effect on graphene’s electron transport
properties. The bicontinuous structure
reduced the frequency of geometricdefects that naturally appear when flat,
hexagonally bonded sheets are formed
into 3D shapes, thus helping to retain
graphene’s 2D electronic character. 3Dgraphene with a large range of poresizes behaved as high-speed quantum
semiconductors, and the random orientations of the graphene sheets eliminatedangular-dependent effects that often
limit 3D device applications.
Ito explains that 3D nanoporousgraphene has particular advantages overother graphene-based devices. “This material has abundant pore space for detecting molecules and promoting chemical
reactions, in addition to its high charge
mobility for applications in electronic devices,” he says. “We expect it could create a
low-cost and ecofriendly alternative to gas
sensors, transistors or energy-harvesting
devices such as lithium–air batteries.”
1. Ito, Y., Tanabe, Y., Qiu, H.-J., Sugawara, K.,
Heguri, S., Tu, N. H., Huynh, K. K., Fujita, T.,
Takahashi, T., Tanigaki, K. & Chen. M. High-quality
three-dimensional nanoporous graphene.
Angewandte Chemie International Edition 53,
4822–4826 (2014).

AIMResearch 2014

RESEARCH HIGHLIGHTS

Nanomaterials

Building bone

The surfaces of bones are often covered
with a thin membrane, which is known
as the periosteum. As well as providing mechanical strength and support,
the periosteum is actively involvedin the regeneration of injured bones.
Osteoblasts — the major cellular component of bone — are produced by thedifferentiation of stem cells residing inthis membrane. However, tissue engineering strategies for bone repair rarely
consider this component of bone.
Inspired by the microstructure of theperiosteum, Xuetao Shi and co-workers
from the AIMR at Tohoku University
and other institutions from around theworld have fabricated an artificial periosteum by using patterned polymericnanosheets1. This material is suitablefor use in bone repair therapies. Natural
periosteum consists of longitudinallyoriented cells and collagen fibers, andthe researchers mimicked this topography by fabricating nanosheets ofpoly(lactic-co-glycolic acid), or PLGA,
which contain grooves with a spacing ofabout 50 micrometers.
Shi and his colleagues were able
to noncovalently anchor the PLGA
nanosheets to a variety of materials
related to bone and bone repair, including a chicken wing bone, titanium alloy
implants, and macroporous and microporous bioceramic tissue engineeringscaffolds (see image). Promisingly, theresearchers found that their nanosheets
were difficult to detach from thesesurfaces. Furthermore, fluorescencemicroscopy revealed that the grooves
in the nanosheets were preserved evenafter the sheets had adhered to bone orbone scaffolds — something that is important for correctly aligning stem cells.

AIMResearch 2014Bone

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Microgrooved polymeric nanosheets stuck to bone implants show promise for
improved bone regeneration and repair

Nanosheet

50 μm
A microgrooved nanosheet adhered to the surface of a bone.

To test whether the PLGA nanosheets
would be suitable for stimulating boneregeneration, the team seeded humanmesenchymal stem cells capable ofdifferentiating into bone onto the artificial periosteum. When they did this,they found that the stem cells aligned
themselves in a parallel orientation to
the grooves.
“The results indicate that the artificial
periosteum not only acts a reservoir ofstem cells for bone regeneration, butalso controls the number of stem cells
that become bone cells,” explains Shi.
Moreover, the microgrooved patternson the nanosheets help direct protein
and gene expression levels of the cultured cells in a similar way to natural

periosteum, which is important forachieving effective bone repair.
The researchers are now planning toinvestigate the bone-generating properties of stem cells on the microgrooved
nanosheets in animals. They expect thatwhen the PLGA nanosheets are adhered
to porous, tissue-engineering scaffolds,
the nanosheets will degrade over thecourse of a month — a sufficiently long
period for the stem cells to correctlyalign and differentiate into osteoblasts.
1. Shi, X., Fujie, T., Saito, A., Takeoka, S., Hou, Y.,
Shu, Y., Chen, M., Wu, H. & Khademhosseini, A.
Periosteum-mimetic structures made fromfreestanding microgrooved nanosheets.
Advanced Materials 26, 3290–3296 (2014).

19

RESEARCH HIGHLIGHTS

Ionic liquids

Going with the flow
Molecular models offer new insight into the flow of ionic liquids in confined spaces

20

Neutral layers

Charged layers© 2014 Royal Society of Chemistry

Ionic liquids are environmentallyfriendly molten salts whose properties
can be fine-tuned by carefully selecting their composite anion and cation
molecules. In some cases, they exhibit
extremely low friction when confined
between two surfaces, making themcandidates for replacing conventional
lubricants in many applications. To
advance their development and commercialization, it is vital to understand the molecular origin of theirlubrication properties.
Now, Filippo Federici and colleagues
from the AIMR at Tohoku University
have theoretically investigated the behavior of the molecules in ionic liquids
confined between two silica surfaces1.
“Our study explores the relationshipbetween the molecular size and shapeof the lubricant, its interaction with thesurface and its frictional response undernanoconfinement,” explains Federici.
The team simulated the behaviors of
two ionic liquids containing the cation
1-butyl-3-methylimidazolium (BMIM).
In one liquid, BMIM was pairedwith the comparably sized anionbis(trifluoromethanesulphonyl) amide(NTF2), whereas the other ionic liquidcontained the much smaller anion
tetrafluoroborate (BF4). Both simulations used neutral crystalline silica surfaces with protruding hydroxyl (OH)groups to confine the liquids.
“The two liquids responded to thesame silica surface in very different
ways,” notes Federici. In particular,
the anion size is critical in determining how the liquid molecules arranged
themselves against the surfaces. As
NTF2 is too large to fit between silica’s
OH groups, the ionic liquid containing

Small anion

Large anion

Large cation

The anion size determines the structure of an ionic liquid confined between two surfaces separated by a
few nanometers.

BMIM and NTF2 forms neutral layers containing equal numbers ofanions and cations. In contrast, theBMIM–BF4 liquid forms a layer of BF4
anions closer to the silica surface, followed by alternating layers of cations
and anions (see image).
Interestingly, this layering affects
the ability of the ionic liquids to flow
between the surfaces. When the BMIM–NTF2 layers flow past each other,similarly charged ions in adjacent layers
face each other, making the structure
unstable and eventually forcing it to rearrange. The BMIM–BF4 liquid is morestable, however, as ions of the samecharge are not brought so close together.
The simulations throw light on a
puzzling experimental result, namelythat BMIM–NTF2, which is less viscous than BMIM–BF4 under normal
conditions, becomes more viscousthan it when the liquids are confined between planes separated by a
few nanometers.
A more realistic model of the silica
surfaces could offer even greater insight.
Currently, the team simulates crystalline
silica with a similar density to that ofglass. However, as glass is amorphous,“its disorder may be an important factor
in the structuring of ionic liquids at theinterface,” explains Federici.
1. Federici Canova, F., Matsubara, H., Mizukami,M., Kurihara, K. & Shluger, A. L. Shear dynamics
of nanoconfined ionic liquids. Physical Chemistry Chemical Physics 16, 8247–8256 (2014).

AIMResearch 2014

RESEARCH HIGHLIGHTS

Graphene

Finding catalytic success withthree-dimensional nanopores
AIMR researchers have discovered
how to unleash the promising catalytic activity of graphene by tweaking
its chemical structure and twisting it
into a three-dimensional (3D) nanoporous framework.
Fuel cells and lithium–air batteries
generally use expensive components,
such as platinum-based electrodes,
to transform oxygen into electricity. Researchers have been consideringgraphene — a single layer of carbon
atoms with metal-like properties — as acheaper alternative. However, progressin this area had been hindered by graphene’s low chemical reactivity.
Now, Yoshikazu Ito, Mingwei Chen
and colleagues from the AIMR at
Tohoku University have developed an
innovative way to turn flat graphenesheets into 3D objects using ‘bicontinuous’ nanoporous nickel templates1.
These materials resemble a type of metallic sponge with flat surfaces infusedwith numerous nanoscale openings,
known as nanopores. Chemical vapor
deposition of benzene gas into thenickel nanopores, followed by acidtreatment to remove the template,
produced 3D graphene — a structurewith an astonishingly high conductivity not far removed from that of its
flat counterpart.
The team uncovered a connection
between small pore size and high conductivity in 3D graphene and realizedthat the build-up of geometric defects
needed to turn flat graphene into 3D
nanopores was playing a role. Because
these defect sites are electronically
active, they conjectured that the sites
could also serve as catalytic reaction sites.

AIMResearch 2014

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Atomic defects in a uniquely shaped material turn graphene into a metal-freecatalyst for fuel cells and lithium–air batteries

0.2 μmTiny nanopores in a three-dimensional graphene structure can serve as catalytic reaction sites forgreen energy technologies.

But to engineer a specific catalytic
response toward the ‘oxygen reduction
reaction’ used to power fuel cells andlithium–air batteries, the researchers had
to introduce foreign nitrogen dopant
atoms into the graphene structure. To
do so, they switched to pyridine gas — abenzene-like molecule with one nitrogenand five carbon atoms — and deposited
it onto the bicontinuous nickel template.
Analytical measurements revealed
that the new, nitrogen-doped graphene
also formed an ordered 3D framework with distinct nanopores (seeimage). When the researchers tested
this material by plunging it into anoxygen-saturated electrolyte solution,
they found that it had superb catalytic
behavior — particularly the samples
with the tiniest possible pore sizes.

“Smaller pore structures require moregeometric defects due to the high-curvature structures they impose,” explains Ito.
“They also contain the highest pyridine
nitrogen atom concentrations, and these
dopant atoms create different kinds ofgeometric defects. This significantly enhances the nanoporous nitrogen-doped
graphene’s catalytic activity.”
The team is now investigating how tofurther unleash the catalytic power of3D graphene nanostructures by directing its activity toward the hydrogen
evolution reaction that also plays a keyrole in batteries and fuel cells.
1. Ito, Y., Qiu, H.-J., Fujita, T., Tanabe, Y., Tanigaki, K.
& Chen, M. Bicontinuous nanoporous N-doped
graphene for the oxygen reduction reaction.
Advanced Materials 26, 4145–4150 (2014).

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RESEARCH HIGHLIGHTS

Polymers

Nanoscale nudges reveal
critical clues
Small variations in mixing at polymer
interfaces can have a large effect on how
devices such as photovoltaic cells andmembranes perform. Dong Wang fromthe AIMR at Tohoku University and colleagues have used an innovative techniqueknown as quantitative nanomechanicalmapping (QNM) to simultaneously
acquire microstructural and mechanicalinformation on polymer interfaces1. This
information may make solving futureadhesion problems significantly simpler.
One of the fundamental issues facing
manufacturers of polymer-based devices
is quantifying how different layers diffuse
and entangle together after processing
treatments. Many analytical techniques
have been developed to study the interpenetration of long molecular chains into
each other’s domains. However, most ofthese methods provide only the concentration gradients of different components.
The interfacial mechanical properties,
which are tightly linked to a polymer’s
applications, are difficult to measure atsmall scales.
Wang and colleagues turned to thecapabilities of atomic force microscopy(AFM) to detail the unique physics ofpolymer interfaces. Normally, researchers
use resonant ‘tapping’ signals from an
AFM probe to trace out detailed, threedimensional profiles of scanned surfaces.
These tapping signals can also gauge themechanical forces between a polymer andthe probe. But such AFM force modes
have slow data acquisition rates andrequire nontrivial analytical techniques toconvert the measured mechanical forces
into material properties.
The newly developed QNM imaging mode for AFM dramatically
speeds up and simplifies mechanical22

Reproduced, with permission, from Ref. 1 © 2014 American Chemical Society

The forces holding multilayered polymer devices together can be mapped using
high-resolution ‘nanomechanical’ probes

4.0 GPa
A new atomic force microscopy imaging technique that reveals how polymer interfaces (green region)
broaden and diffuse over time provides information that may help extend the lifetimes of devices such as
plastic solar cells.

measurements by detecting the maximum force applied to a surface during aprobe tap. Then, by using this ‘peak force’signal as a damage-preventing feedback
control loop, the tapping signals can
scan rapidly across a sample and map
out regions of different physical force
with nanoscale precision.
The researchers examined interfaces
formed between poly(vinyl chloride)and poly(n-butyl methacrylate), twoplastics that are fully mixable, to test for
diffusion-induced effects with QNM. The
resulting nanomechanical maps revealed
clear stiffness signatures of the polymer
components and a distinct bulge at theinterface (see image). By tracking how
this zone broadened and mechanically
deformed over time, the team acquired

a wealth of new physical and chemical
data: the interface’s diffusion kinetics,
microstructures and glass transition
temperatures were identified with aten-nanometer resolution.
“What is most striking about this method is its ability to assess small differencesin the mechanical properties of materials
over very short length scales using highresolution AFM,” says Wang. “This has
not been possible previously and provides
a new route to investigate the bonding
between polymer multilayers.”
1. Wang, D., Liang, X., Russell, T. P. & Nakajima, K.
Visualization and quantification of the chemicaland physical properties at a diffusion-induced
interface using AFM nanomechanical mapping.
Macromolecules 47, 3761–3765 (2014).

AIMResearch 2014

RESEARCH HIGHLIGHTS

Biosensors

A gentler route to hydrocarbon
electrodes
A new technique for creating amorphoushydrocarbon films that employs much
milder conditions than conventional
methods has been applied by Yoshiyuki
Kikuchi and colleagues of Seiji Samukawa’s
and Tomokazu Matsue’s laboratories at
the AIMR, Tohoku University to fabricate
electrodes for electrochemical sensors1.
Amorphous hydrocarbon films arepromising for use as components inbiomedical sensors, as they are biocompatible, chemically stable and conduct
electricity well. These properties makethem suitable as electrode coatings insuch sensors. But conventional techniques for creating amorphous hydrocarbon films require high temperaturesand plasma — a gaseous soup of charged
particles — both of which can damage
the semiconductor substrates beneaththe films.
The new technique uses two reaction
chambers separated by a perforated barrier (see image). Argon gas is injected into
the upper chamber, where microwaves
excite it to form a plasma containing positive argon ions. Meanwhile, the carbonbased compound toluene is injected into
the lower chamber, from where it leaks
into the upper chamber through the holes
in the barrier.
The positive argon ions partially breakup the toluene molecules, which thenreturn to the lower chamber and adsorb
on a silicon substrate at a temperature of–50 degrees Celsius. Argon ions follow thesame path, but pick up an electron as they
pass through the perforated barrier, creating a stream of neutral argon atoms; thisneutralization technology of argon wasdeveloped by Samukawa’s group in 2000.
These atoms hit the carbon-based fragments stuck to the silicon, helping to knit

AIMResearch 2014

© 2014 Yoshiyuki Kikuchi

A new deposition technique has been used to form conducting films for detecting
biological molecules

A new deposition technique allows amorphous hydrocarbon films to be fabricated under much milder
conditions than conventional methods.

the molecules together into a continuous
film. Crucially, the perforated barrier
blocks any ultraviolet light emitted by theplasma, which would otherwise damage
the precursor molecules and substrate.
The researchers found that the film wascomposed of an interconnected networkof molecules called polyaromatic hydrocarbons and could conduct electricity
reasonably well. Tests showed that thefilm had a low electrical resistance andfast electron transfer, ideal properties foran electrochemical sensor.
The team improved the techniqueby producing just the right balance ofpressures between the two chambers, toenable ideal mixing of argon and toluene.
They also boosted the film’s conductivity by adding nitrogen gas to the argon
stream — this probably resulted innitrogen atoms being incorporated into
the finished film, a process called nitrogen doping that helps make the material’s
electrons more mobile. “Nitrogen doping
improves the electrode performance,”
explains Kikuchi.
The researchers are currently collaborating with another group to develop an
amorphous hydrocarbon electrode for asensor that could be used for a range of
bioimaging applications, such as tracking the release of neurotransmittersfrom neurons.
1. Kikuchi, Y., Wada, A., Kurotori, T.,
Nakano, M., Inoue, K. Y., Matsue, T., Nozawa, T. &Samukawa, S. Conductive amorphous hydrocarbon film for bio-sensor formed by low
temperature neutral beam enhanced chemical
vapor deposition. Carbon 67, 635–642 (2014).

23

RESEARCH HIGHLIGHTS

Graphene

Customized from the bottom up

An interdisciplinary team has devised
a way to self-assemble defect-free graphene nanostructures right where they
are needed by exploiting the reactiondirecting properties of copper surfaces1.
This is a significant advance since highspeed graphene transistors can outpace
current silicon technology, but fabricating these atom-thin sheets of carbon into
device structures had been problematic.
The team, which is led by Patrick Han
and Taro Hitosugi from the AIMR at
Tohoku University, is investigating experimental materials known as graphene
nanoribbons (GNRs) for use in tinytransistor devices. The electronic states ofthese narrow graphene strips strongly depend on the atoms bordering their edges.
A GNR is semiconducting when the edge
carbons bond into an ‘armchair’ configuration, whereas a ‘zigzag’ configuration ofedge carbons produces a metallic GNR
with quantum confined spin states.
Because conventional circuit lithography inevitably introduces defects into
GNRs, recent studies have exploreda more direct, ‘bottom-up’ approach— growing graphene strips atom by atom
by depositing molecular precursors onto
metal surfaces. Typical strategies use
chemically active precursors with relatively inert gold and silver substrates togive molecules many chances to interact
with one another. But these methods haveso far produced only armchair GNRs.
To synthesize zigzag nanoribbons, theresearchers investigated whether a morereactive copper surface could direct amolecular polymerization reaction. “Onsurfaces like copper, molecules are lessfree to diffuse randomly and are more
inclined to interact with an ordered lattice of metal atoms,” explains Han.

24

© 2014 Patrick Han

A surface-assisted chemical reaction gives unprecedented control over graphene‘nanoribbons’ for future nanodevices

20 nm
Scanning tunneling microscopy image of self-assembled graphene nanoribbons on a copper surface. The‘zigzag’ ribbon structures are highlighted by white lines in the high-resolution inset.

The researchers deposited precursors
known as 10,10’-dibromo-9,9’-bianthryl monomers onto a copper surface
and then used atom-resolved scanningtunneling microscopy to scrutinize
the structures of samples produced at
different annealing temperatures. They
discovered that at room temperature
the precursors self-assembled into
narrow chains that preferentially grewin only six directions along the copper
lattice. Stepwise heating to 500 degrees
Celsius caused these chains to bunch
into islands before joining up into
periodic regions of zigzag nanoribbons(see image).
Further experiments revealed that thebromine atoms on the precursor helped
hold the molecules into the zigzag arrangement at high temperatures until

the graphene polymerization reaction
occurred at 500 degrees Celsius. Thisis surprising since copper surfaces normally break off bromine atoms from aromatic molecules at room temperature.
The scientists anticipate that the finecontrol over nanoribbon length, direction and edge conformation this technique offers will spur more studies into
surface-directed chemistry. “By exploiting the properties of a reactive surface,
we can determine which nanoribbon
structure will form and restrict its
growth to specific directions,” says Han.
1. Han, P., Akagi, K., Canova, F. F., Mutoh, H.,
Shiraki, S., Iwaya, K., Weiss, P. S., Asao, N. &Hitosugi, T. Bottom-up graphene-nanoribbon
fabrication reveals chiral edges and enantioselectivity. ACS Nano 8, 9181–9187 (2014).

AIMResearch 2014

RESEARCH HIGHLIGHTS

Electrochemistry

Mapping a battery electrodeA powerful new imaging technique
has mapped the reactivities related tolithium-ion transport in an electrodefor the first time, which will lead to battery designs with higher performances.
Lithium-ion batteries are widely used
to power mobile devices, but some aspects of their operation are still veiled.
Studying the interaction between
lithium ions and electrodes has been
particularly challenging due to a lackof suitable analytical techniques formeasuring reactivities.
Now, Tomokazu Matsue, Yasufumi
Takahashi and Akichika Kumataniof the AIMR at Tohoku University
and colleagues have developed anano-scanning electrochemical cell
microscope that can record the electrochemical properties of a lithium iron
phosphate (LiFePO4) electrode1. “Thisis the first time anyone has visualized
the reactivity of an electrode surface,”says Takahashi.
The microscope uses a pipette probe
whose aperture diameter is roughly
50 nanometers. The probe contains a solution of lithium ions and scans slowly
across the electrode surface. Whenever
the solution within the nanopipette
touches the electrode, lithium ions flow
between the two, creating an electricalcurrent. This allowed the researchers
to map an electrode’s landscape to ascale of about 100 nanometers and toinvestigate its electrical properties at
specific points.
The team tested their device on a
typical electrode containing a blendof LiFePO4 and acetylene black.
While being cheap and environmentally benign, LiFePO4 suffers from a
low electrical conductivity. Acetylene

AIMResearch 2014

Modified, with permission, from Ref. 1 © Y. Takahashi et al.

Microscopy technique tracks the flow of lithium ions in a common
cathode material

Scanning electrochemical cell microscopy is used to map the topography of a lithium iron phosphate particle
in a battery electrode (left), as well as measure the current that flows into it (right; red corresponds to the
maximum current of 143 picoamperes).

black improves the electrode’s conductivity, but it reduces the battery’s overall
energy capacity since it cannot store
lithium ions.
The nano-scanning electrochemical cell microscope confirmed thatlithium ions flowed readily into micrometer-sized LiFePO4 particles thatwere embedded in the electrode, but
did not enter regions made of acetylene
black. The probe was sensitive enoughto target individual particles, without
interference from neighboring materials (see image).
By altering the concentration oflithium ions in the electrode, thenanopipette probe could also reveal
how charging or discharging affected the voltage at specific pointsof the electrode. Stringing together
snapshots of the process taken every

10 milliseconds produced a movie ofan individual LiFePO4 particle’s electrochemical behavior.
The researchers also analyzed
individual nanoparticles of LiFePO4
on a platinum plate to discover how
the crystal structure and particle
orientation affected the way lithium
ions flowed through it. They are now
carrying out further experiments onthese properties, which might help to
optimize the position and structure of
LiFePO4 particles in electrodes to boost
battery performance.
1. Takahashi, Y., Kumatani, A., Munakata, H.,
Inomata, H., Ito, K., Ino, K., Shiku, H.,
Unwin, P. R., Korchev, Y. E., Kanamura, K. &Matsue, T. Nanoscale visualization of redox
activity at lithium-ion battery cathodes.
Nature Communications 5, 5450 (2014).

25

RESEARCH HIGHLIGHTS

Microscopy

Ultrasharp probing of solar cells

An international team has captured
unprecedented, three-dimensional (3D)
images that reveal how polymers areorganized in ‘bulk heterojunction’ (BHJ)
organic solar cells1 — one of the mostpromising green devices for generating
renewable electricity in an economically
viable way. These new images can help
settle long-standing debates on how
molecules assemble at electrode interfaces, leading to improved manufacturing strategies.
The light-harvesting componentsof BHJ organic solar cells containtwo materials that possess opposing
electron-accepting
and-donatingabilities. To ensure efficient collectionof solar energy, these materials mustbe blended until they are separated by
no more than a few tens of nanometers.
Most analytical techniques, however,can observe blended regions only in flat,
two-dimensional planes, whereas actual
devices are 3D.
Now, Dong Wang, Ken Nakajima
and Thomas Russell from the AIMR at
Tohoku University have used atomic
force microscopy (AFM) to explore morphologies inside BHJ devices. AFM employs tiny needle-like probes to trace thetopology of 3D surfaces, but it normallyhas trouble resolving polymer structuresat molecular levels. The team overcame
this limitation by using ultrasharp AFM
tips that, as they are only a single nanometer wide, can image incredibly finedetails on surfaces.
The researchers first prepared a standard BHJ device containing an aromaticelectron-donor polymer known as PTB7
and a ‘buckyball’-like electron-acceptor
material called PCBM. They thenexposed the kinetically active working

26

20 nm

An atomic force microscopy phase image showing the arrangement of polymer crystals inside solar cells witha nanometer-scale resolution.

layers inside the BHJ by using highenergy argon ions to etch away the outerlayers of the polymer blend.
Subsequent AFM, X-ray scatteringand electron microscopy measurements
revealed that the device’s active layer
contained a continuous network of PTB7
fibrils, separated by tens of nanometers,interpenetrated by pathways of PCBM
strands. This morphology changed at
the electrode-contacting outer surface,where PTB7 crystals formed with
PCBM aggregates embedded in-between(see image).
The researchers prepared devices containing different proportions of PTB7
and PCBM and discovered that the solar
conversion efficiencies of these devices
corresponded neatly to the length scalesof the morphologies observed by AFM.

According to Wang, this is clear evidence
that three main factors — the PTB7
fibrils, the PCBM network, and the active mixing region — must be optimized
to produce high-performance organic
solar cells.
“These morphologies suggest thatnext-generation polymers need fibrilswith fewer defects and better connectivity,” says Wang. “For the acceptor side, new materials that can form
better and finer network domains will
prove critical.”
1. Wang, D., Liu, F., Yagihashi, N., Nakaya, M.,
Ferdous, S., Liang, X., Muramatsu, A., Nakajima, K.
& Russell, T. P. New insights into morphology ofhigh performance BHJ photovoltaics revealedby high resolution AFM. Nano Letters 14,
5727–5732 (2014).

AIMResearch 2014

Modified, with permission, from Ref. 1 © 2014 American Chemical Society

High-resolution atomic force microscopy reveals the inner workings of low-cost
photovoltaic devices

IN THE SPOTLIGHT
The AIMR has grown rapidly since its inauguration in 2007,
now with over 150 leading researchers from all over the world,
including 30 internationally renowned principal investigators who are charged with pioneering new and innovative
breakthroughs in materials science. The institute is also
active in developing young, promising researchers with afocus on strong cross-disciplinary collaboration and creativity. AIMResearch spotlights these talented researchers of thepresent and future, detailing their daily research activities andscientific ambitions.

IN THE SPOTLIGHT

Published online on 31 March 2014

INTERNATIONAL SYMPOSIUM

Materials–maths fusion researchenthuses symposium attendees
The AIMR International Symposium (AMIS) 2014, held in Sendai on 17–19 February, showcased how the institute’s
unique brand of mathematics–materials fusion research is already making positive contributions to societyThe main objective of AMIS 2014 was
to share discoveries from the AIMR’s
recent institute-wide infusion ofmathematics into materials science research
while learning from other innovators in thefield. Leading experts in materials sciencefrom Japan and overseas attended thegathering to explore the theme “Toward
emergence of new materials science withmathematics collaboration.” Preserving thestrong international interest of the previous
year, the 236 participating researchers represented 52 organizations and 13 countries.
Susumu Satomi, president of Tohoku
University, welcomed the participants.
In his address, he emphasized the crucialrole of the AIMR in upholding Tohoku
University’s commitment to research by“creating a new paradigm of ‘mathematicsdriven materials science’. ” Satomi added:“In particular, materials science cancontribute enormously to society, creatinga basis for green materials and cultivating
the potential of natural energy resources
to resolve environmental problems.”
Essential to achieving this goal, he noted,
was the AIMR’s extensive global network,with 22 overseas partner institutions,
including its AIMR Joint Research Centersat the University of Cambridge, UK; theUniversity of California, Santa Barbara(UCSB) in the US; and the Instituteof Chemistry, Chinese Academy of
Sciences, China.
Speaking next, Akira Ukawa, deputy
program director of the World PremierInternational Research Center Initiative(WPI), further underscored the importanceof fundamental and innovative science forsocietal development. Ukawa highlighted

28

Almost 240 researchers from over 50 organizations and 13 countries attended the AIMR International Symposiumin Sendai in February 2014 to share knowledge under the banner of “Toward emergence of new materials science
with mathematics collaboration.”

the many ideas that have emerged from thereciprocal influence between mathematics
and experimental science, such as thetheory of relativity and quantum mechanics. “Mathematics and the sciences aremost fruitful when they work together andcollaborate together,” he said. “So be ambitious. History is on your side.”
In her welcoming address,
AIMR Director Motoko Kotani shared thestory of the AIMR’s transition toward acollaborative materials and mathematics research culture, which she initiated in 2011.
“It took us two years to reorganize our internal structures,” she said. One of the critical moves was the establishment of three
Target Projects, which use mathematics toclarify principles and mechanisms behind

physical systems, and that were carefully
selected for their potential to flourish in
the new context of fusion research. These
reforms have already enabled fluent
interdisciplinary exchange, said Kotani,a trained mathematician herself. “We arevery happy that, with this symposium, we
can share some of our emerging results.”
Powerful prose
The day’s program proceeded with a series
of invited speakers. Hirosi Ooguri of the
California Institute of Technology, US,
and the Kavli Institute for the Physics andMathematics of the Universe, the Universityof Tokyo, drew on his decades of work at
the interface of mathematics and theoretical physics to share some unexpected

AIMResearch 2014

IN THE SPOTLIGHT

connections. “Mathematicians look forthings that are universal. Physicists want
immediate results,” said Ooguri. Given the
differences in the terminology, motivation
and work habits of mathematicians andphysicists, he stressed the importance oftranslating a problem from one ‘language’to the other to improve the potential to finda solution.
Chemist Håkan Wennerström from
Lund University in Sweden began bydetailing findings on the non-equilibrium
formation processes of mesoporous
particles — materials that contain pores of
2–50 nanometers in diameter. Moving on
to describe the presence of non-equilibrium
systems at air–water interfaces where water
evaporates, such as the surface of the skinor eye, Wennerström noted that understanding this phenomenon could translate
into the improved delivery of drugs.
Speaking next was Steven Louie, a condensed matter physicist from the Universityof California, Berkeley in the US. Louie
focused on his recent work on graphene, amaterial composed of an atom-thick sheetof carbon. Graphene is remarkably strong,light and transparent, and conducts heatand electricity with negligible resistance.
Louie moved on to discuss findings on
the optoelectronic properties of graphene,
which will enable exciting new generationsof electronic devices.

Presentations by the final two opening
speakers demonstrated the powerful abilityof mathematics to fuel discoveries in materials science. Physicist Qi-Kun Xue, vicepresident of Tsinghua University in China
and a principal investigator at the AIMR,
related his experimental confirmation of
the quantum anomalous Hall effect in magnetic topological insulators — somethingthat had previously been only a theoreticalconjecture. “This observation completes all
the three quantum Hall effects,” noted Xue.
James Langer, a theoretical physicist
from the UCSB, wrapped up the opening
session by offering insight into the dynamics of glass using a mathematical model.
“The glass bubble is the most incredibly
beautiful, important and deep mystery thatfaces us in classical physics these days,”said Langer. To address this challenge, “wehave to focus on really simple and realistic
models of glass-forming materials.”
Small energy: Big impact
AMIS 2014 spanned 3 days and featured
6 plenary sessions, 4 parallel lecture tracks
and a poster session. A total of 32 scientists
from 6 countries spoke about subjects
ranging from non-equilibrium systems
and mathematics to soft materials andenergy materials, while almost 100 posters
revealed the latest findings from researchersat the AIMR.

James Langer, theoretical physicist from the University of California, Santa Barbara in the United States offered
new insight into the dynamics of glass using a mathematical model.

AIMResearch 2014

Akira Ukawa, deputy program director of the World
Premier International Research Center Initiative (WPI),
delivered a historical take on the potential rewards ofmerging materials science research with mathematics.

Masaru Tsukada, administrative directorof the AIMR, brought the events to a close.
In his presentation, he introduced a fourthTarget Project — Core Technology for Nano
Energy Devices — newly created to ensure
the transfer of materials science research
for the benefit of society. The project willdevelop systems for renewable energy applications and innovative processing technologies for sustainable, green materials. In his
valediction, Tsukada extended an invitation
to all participants to return to Sendai fornext year’s symposium, AMIS 2015, scheduled to be held on 17–19 February.
The symposium marks the end ofanother busy year for the AIMR. “When
we first embarked on our reorientation,
the WPI’s progress report said that while
our proposal was attractive, they wereconcerned about whether our plan could
be realized,” reflected Kotani, speaking after
the event. “This year, the report notes that
the AIMR has progressed much faster than
expected.” Among its many achievements
in 2013, the institute published particularly
novel research on bulk metallic glasses inScience. Kotani predicts that the AIMR’s
new direction will result in further breakthroughs in understanding of the structure
and properties of a host of materials,
including graphene, carbon networks andnanoporous gold. “We took the right direction,” asserted Kotani. “This is one of ourstrong beliefs.”

29

IN THE SPOTLIGHT

DIRECTOR’S INTERVIEW

Published online on 26 May 2014

Exporting mathematics–materials
collaboration research to the world
Under Director Motoko Kotani’s leadership, the AIMR has made mathematics–materials research a global priority

Tjoint research centers, partner institutions
and inter-faculty exchange agreements.
What have these various forms of cooperation achieved?

AIMResearch: The AIMR continues todevelop its international network throughAfter taking on the directorship, I
introduced a program of joint research
centers where postdoctoral researchers
can conduct collaborative research.
Of the 15 international institutes withwhich the AIMR has already establishedagreements, we have built closer relationships through three of the joint research
centers in particular: the University of

wo years ago, the AIMR welcomedmathematician Motoko Kotani
as its new director. Since then,the institute has established itself globally through its innovative focus onmathematics-flavored materials science
research. AIMResearch spoke to Kotani
about her successes in extending the
AIMR’s overseas reach through strong
research partnerships and creating aninternational work culture.

Motoko Kotani, director of the AIMR.

30

Cambridge in the UK, the Universityof California, Santa Barbara (UCSB) in
the US, and the Institute of Chemistry,
Chinese Academy of Sciences. These centers have significantly contributed to ourglobal visibility through the publicationof research and co-organizing workshopsthat bring recognition to the researchers involved as much as the institutes
they represent.
AIMResearch: What plans do you
have to extend such partnerships in the
coming years?
In 2014, we will organize a workshop
with the Australian National University
and a Tohoku Forum at the University ofCambridge, which will integrate researchfrom the AIMR and our host institute,
Tohoku University.
Since we are not a very large institute,our emphasis is on enhancing — as
opposed to expanding — our global
network. One way that we strengthen thedepth of our collaborations is by setting
common research agendas with our partners that create a bridge for the two-way
exchange of information and researchers.
We are establishing a new joint research center at the University of Chicago
in the US and are in discussion with the
Chinese Academy of Sciences to create
another laboratory in Beijing, together
with Tsinghua University. We would
also like to extend our relationship with
Fraunhofer-Gesellschaft beyond current
agreements with three of the organization’s institutes. I would like the AIMR tomove toward more joint research throughshared grants that can be divided between
two countries, for example.

AIMResearch 2014

IN THE SPOTLIGHT

During her tenure as director of the AIMR, Kotani has set a new direction for the AIMR through mathematics-driven materials research.

AIMResearch: The AIMR is recognized for
cultivating a fertile environment for the freeexchange of ideas and every year attracts
more of the brightest minds from all over the
globe. How have you managed to create suchan open and inclusive research atmosphere?

AIMResearch: According to the latest WPI
program review, the AIMR has made“remarkable progress” since introducing
a new mathematics–materials approachto research in 2012. How were you able toachieve so much so quickly?

Creating a favorable environment for
research is crucial to science. Many
researchers are interested in coming toJapan because of its reputation for highquality research but are deterred by thelanguage barrier. Here at the AIMR, theworking language is English. The highly
motivated staff at our administrative office help foreign researchers to transition
to and settle in Japan, and provide themwith essential information and support
services for maneuvering the grant application system. In addition, we haveinitiated a scheme of jointly appointing
academics with external partner universities, which affords researchers increasing
flexibility and mobility.
Furthermore, I offer many incentives to active researchers. Here at the
AIMR, successful researchers receive
merit-based benefits like more research
space or a salary increase. This attracts
very ambitious individuals — the kind ofresearchers I want at the AIMR.

Since the establishment of the AIMR, ourresearchers have been making commendable progress in taking their research
to the next level. Creating a new vision
for the AIMR through our mathematics–materials approach allowed us toamalgamate their collective achievements
and to direct our resources and research
power toward a common goal, thereby
multiplying the strengths of the institute.
Materials science is a very complex andwide-ranging research area, which makes
it impossible to be recognized worldwide
across all areas of the field. Therefore, we
decided to focus on a few target projects
that fit within the mathematics–materials
framework. We have identified problems to be studied that are challenging— but also very attractive — from theviewpoints of both mathematics andmaterials science.

AIMResearch 2014

AIMResearch: 2014 marks the eighth yearof a ten-year funding commitment to the

AIMR from the WPI program. What plans
do you have to ensure the long-term futureof the institute?
I have met several times with
Susumu Satomi, president of Tohoku
University, to highlight the AIMR’s contributions to Tohoku University. Despite
the AIMR’s small number of principal
investigators, half of whom are fromabroad, we bring in 5–6 per cent of theexternal research funds generated by theuniversity. I think that this is remarkable.
Convinced by the AIMR’s significant
contribution to system reforms at
Tohoku University, the president formally committed the university to establishing a new permanent framework that
focuses on globalized, interdisciplinary
research across several areas, including
mathematics and materials science. The
organization will be established in a
few months.
The long-term sustainability of the
AIMR is very important, especially foryoung researchers who have only just set
out in our new direction. They are doing
very good work and it is my responsibility to help them to continue with theirresearch — and what better place thanhere at the AIMR?

31

IN THE SPOTLIGHT

INTERNATIONAL SYMPOSIUM

Published online on 28 July 2014

World-leading WPI initiative
showcases materials scienceinnovation at E-MRS Spring Meeting
An attentive audience met researchers from the AIMR at the annual Spring Meeting of the European Materials
Research Society in FranceF

rom a new spin on electronics totiny biological superhighways andbeaming carbon-based transistors,
researchers from the Advanced Institute forMaterials Research (AIMR) presented theirvision of the future of materials science atthe 2014 Spring Meeting of the European
Materials Research Society (E-MRS), the32nd in a series of annual meetings held
since 1983. “The E-MRS Spring Meeting is
one of the most important conferences onmaterials science for the global community,” notes Masaru Tsukada, administrative
director at the AIMR.
T h is ye ar’s me e t i ng , hel d on
26–30 May 2014 in Lille, northern France,
was the society’s largest gathering since its
establishment in 1983. Among the estimated 3,100 participants was a 44-strong
team from Japan representing the World
Premier International Research Center
Initiative (WPI), a funding body that supports centers of excellence in basic science.
The four WPI participating institutes— the AIMR, the International Center for
Materials Nanoarchitectonics, the Institutefor Integrated Cell-Material Sciences andthe International Institute for CarbonNeutral Energy Research — shared theirlatest research with an attentive international audience at the meeting. Fourteen
researchers from the AIMR — the highest
number among the WPI institutes — gave
presentations in subjects that included spintransport, protein vehicles and organic
superconductors.
The highlight of the WPI team’s schedule was a half-day symposium titled “Japan

32

Eiji Saitoh shared his expertise in spintronics technology at the 2014 E-MRS Spring Meeting in France.

in Motion.” Through a series of talks, thescientists introduced new ideas that are
seizing the materials science community,from an atomic and molecular control approach to designing new structures basedon nanoscale building blocks, to the successful alliances between materials scienceand mathematics that have emerged from a
directed shift toward fusion research.
“Japan in Motion was a huge success,”says AIMR director, Motoko Kotani, whoat the meeting was approached by many
researchers eager to collaborate with
the AIMR or move to Japan to conduct
research at the institute. The symposium itself attracted an impressive 70 participants,
and 400 individuals visited the associated
WPI booth, including the current E-MRS

president, Thomas Lippert, and former
president, Ian Boyd.
Conducting spin
In addition to the Japan in Motion event,
WPI researchers shared their researchat sessions organized over the course of
the five-day meeting. In his presentation,
Eiji Saitoh, a principal investigator at the
AIMR, introduced his recent contributions
to the technology of spintronics.
Spintronics seeks to manipulate theproperties of spin and charge inherent
in electrons for microelectronic device
production. The technology is used in allcommercially available disk drives today,
and increasing control over electron spin
could lead to even speedier data transfer

AIMResearch 2014

IN THE SPOTLIGHT

and denser storage capacities. “The AIMR
is one of the strongest institutes in theworld for spintronics research,” says Saitoh.
Saitoh’s research builds on observations made in the early eighteenth century by German physicist
Thomas Johann Seebeck, who discoveredthat temperature differences in a conductor can generate an electric current — aphenomenon aptly named the Seebeck
effect. In 2008, Saitoh led the team ofresearchers that observed an analogous
effect in electron spins in a magnet, identified as the spin-Seebeck effect. He hassince been able to generate and measurea spin ‘voltage’ resulting from a change intemperature in a metal or insulating ferromagnet, an effect that could be exploitedin spintronic devices or to improve the efficiency of existing heat sensors and waste
heat recycling systems.
Intrigued by Saitoh’s presentation,a researcher from Germany suggested
a method that could be used to control
molecular spin. In a separate session, an
independent investigator at the AIMR,
Shigemi Mizukami, also shared his success in growing new manganese-basedmaterials that could lead to terahertz-scale
spintronic devices.
Protein porters
Improving energy efficiency by drawing
inspiration from nature was central to
the work presented by Aurélien Sikora,
a research associate at the AIMR.
One natural system that ranks especially high on the energy-efficiency ladderis the motor protein kinesin — the subjectof Sikora’s research. “Nature has a lot toteach us,” says Sikora. “The efficiency of
motor proteins in energy conversion is
unbeatable. We have to understand how
to achieve such a level of performance toreduce energy waste and pollution.”
When loaded with goods, kinesin walks
along microtubule roadways to transport
its cargo throughout the cell. By turningkinesin proteins on their backs, scientists
have been able to send microtubules‘crowd surfing’ on the collective movementof the upward-facing kinesin legs. Sikora
and his colleagues were able to demonstrate for the first time the potential for improving control of microtubule movement

AIMResearch 2014

Researchers from around the world visited the WPI booth to find out how they could collaborate withinterdisciplinary research centers in Japan like the AIMR.

by confining the kinesin motors to narrow
tracks made of carbon nanotubes.
Looking ahead, Sikora believes thatusing carbon nanotubes for protein-basedtransport could one day make it easier tocontrol nanoparticle movement in biomedical devices, for example in conjunction
with an electric field. Many participantsat the E-MRS meeting were particularlyinterested in this ability to align the carbon
nanotubes and asked numerous technicalquestions about Sikora’s findings.
Organic benefits
A host of other fascinating materials were
presented by AIMR researchers at the
E-MRS meeting. Among them, principal
investigator Mingwei Chen discussed
the many merits of nanoporous metals fabricated through a process called
dealloying, which gives them mechanicalrigidity, a large surface area, electricalconductivity and high resistance to corrosion. And Taro Hitosugi, an associate
professor, shared his findings from atomiclevel investigations of a class of materials
known as transitional metal oxides thatexhibit compelling electron transport andmagnetic properties.
In his poster presentation, Thangavel
Kanagasekaran, a research associate at the
AIMR, revealed he had successfully demonstrated an organic field-effect transistor
that emits bright light at room temperature.
Combining the ability to generate lightwith the electrical switching functionalityof a transistor, this new class of optoelectronic device could improve visual display
technologies and optical communication
systems, and ultimately lead to the realization of electrically pumped organic lasers,
he reported.
Kanagasekaran and the other AIMR
and WPI delegates found that the interdisciplinary gathering in France offeredan ideal venue to share ideas with theirinternational counterparts. “All of theinvited speakers from the AIMR took
part in active and fruitful discussions with
their peers,” adds Director Kotani. “Ourengagement with this interdisciplinary
community has been very meaningful,and we will continue to pay attention to
its activities.”

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IN THE SPOTLIGHT

INTERNATIONAL PARTNERSHIPS

Published online on 29 September 2014

Material benefits from US
connections
The AIMR crosses the Pacific to strengthen its research ties with institutes in the United StatesT

wo years ago, AIMR Director
Motoko Kotani initiated the consolidation of the institute’s many
international alliances into focused centers for collaborative, multidisciplinaryand high-impact research. This year,that effort continues with the introduction of an exciting new venture in the
United States.
On 16 April, the AIMR signed anagreement to establish a joint research
center with the University of Chicago,
expanding on its three existing partnerships with the University of Cambridge,
the Institute of Chemistry at the Chinese
Academy of Sciences and the Universityof California, Santa Barbara (UCSB).
As well as enabling the two-way transmission and generation of knowledge
through joint laboratories, workshops
and researcher exchanges, this new connection further reinforces the strong relationship between two leading researchers

in the field of spintronics — Hideo Ohno
and David Awschalom. Ohno, a principal
investigator at the AIMR, was the firstto discover ferromagnetism in a superconductor, and he later developed anelectrical ‘switch’ for turning a permanent
magnet on and off. And Awschalom, aprincipal investigator at the Universityof Chicago’s Institute for MolecularEngineering (IME), experimentally observed a phenomenon known as the spin
Hall effect, which had been theoretically
predicted over 30 years earlier. These andmany other electron-spin-related discoveries in the last decades can enable faster
information processing and data storagein spintronic devices.
Radical approach
The new Chicago relationship adds to an
existing international partnership in the
United States with UCSB. Researchers at
the AIMR–UCSB joint research center

AIMR Director Motoko Kotani (left) and Eric Isaacs, provost of the University of Chicago, signed a joint agreement
on 16 April 2014 to establish a joint research center.

34

are making unexpected connections inorganic electronics, which may spawn anentirely new area of research.
As most organic radicals are highly
unstable, researchers have tended to avoid
investigating their potential for organic
electronics. But Fred Wudl, chemistry andmaterials professor at UCSB and adjunctprofessor at the AIMR, wondered whether
these radicals could be used in electronic
devices. He posed the challenge of exploring this idea to AIMR–UCSB joint
scientist Yonghao Zheng, who is currently
based at Wudl’s lab in Santa Barbara. The
exercise proved worthwhile — Zheng
discovered that the electronic propertiesof a stable organic radical can be simply
altered by changing its temperature.
“This is a really exciting finding andcould open up a new area of research fororganic electronics,” says Zheng. Organic
materials are particularly attractive foruse in electronics because their properties
can be fine-tuned much more easily thaninorganic materials, and they can be mass
produced using simple, low-cost methods.
Eventually, these materials could bring us
flexible television screens and transparent
photovoltaic wallpaper. “Organic electronics have the potential to make our lives
more beautiful,” says Zheng.
Connecting researchers
In addition to studying the electronic
properties of organic radicals, Zheng
pl ans t o i nve s t i g at e t h e i r m a g netic properties by collaborating witha principal investigator at the AIMR,
Katsumi Tanigaki, an expert on magnetism. Zheng also hopes to engage withthe mathematicians at the AIMR to gaina better understanding of the reasons

AIMResearch 2014

IN THE SPOTLIGHT

AIMR–UCSB joint scientist Yonghao Zheng has discovered that the electronic properties of a stable organic radical
can be simply altered by changing its temperature.

behind the phenomena he observes
experimentally. A similar partnershiphas already been established at the AIMR
between Hiroyuki Isobe, a principal investigator in the area of organic synthesis,
and Director Kotani, who is a mathematician. Recently, this pair used geometry todescribe and measure the length of finitesized carbon nanotube molecules. “TheAIMR is like one big family,” says Zheng.

David Awschalom, a pioneer in the field of spintronics
at the University of Chicago, presented his recent workat the first joint research center workshop organized
between the University of Chicago and the AIMR.

AIMResearch 2014

“Everyone works very closely together,which really speeds up research.”
Besides inspiring groundbreaking
research, the collaboration between UCSB
and the AIMR has benefited early career
researchers like Zheng in many ways. “Asa joint scientist, I have access to fabulous equipment at the UCSB Materials
Department and can exchange ideas with
top-level professors.” The experiencehas expanded his research network andbroadened his perspective. Crucial to thatprocess have been the regular meetings
and workshops between the two institutes,
particularly the joint seminar hosted by
UCSB in January 2012, with the AIMR
returning the favor in February 2013.
Quanta of information
In September this year, the AIMR organized a workshop to deepen their new
alliance with the University of Chicago.
“The AIMR is thrilled to enter into its
first international partnership with the
University of Chicago and to strengthen
its relationships through the workshop,”says Kotani, who opened the session.
Throughout the two-day event, chemists,
physicists, mathematicians and materials
scientists deliberated on a host of topics,
including the quantum manipulation ofmatter, energy harvesting and storage, andthe mechanics of breathing.

Among the presenters at the meeting
was Shin-Ichi Orimo, a principal investigator at the AIMR, who highlighted thestable and fast conduction properties oflightweight complex hydrides, which could
be exploited for hydrogen storage as wellas in lithium rechargeable batteries. Also,
Ka Yee Lee, a professor at the Universityof Chicago, shared her research on lungsurfactant, a lipid and protein complex thatcoats the alveoli and eases breathing by reducing surface tension. Her research could
help to improve the design of artificial lungsurfactants to treat diseases characterized
by surfactant deficiency.
“The inaugural workshop highlighted
a variety of emerging research opportunities where we hope to develop productive
collaborations with our colleagues in
Sendai, driven by young researchers fromboth institutes,” says Awschalom, who
is now taking spintronics into the realmof quantum information engineering.
Awschalom was one of six participantsfrom the University of Chicago who traveled to Japan to exchange ideas with six
counterparts from the AIMR.
Also from the University of Chicago,
Professor Andrew Cleland discussed his
latest successes in harnessing quantummechanical phenomena for the development of nanomechanical systems anddevices. Cleland’s team was the first to
construct a machine whose movement
followed the peculiar laws of quantum
mechanics, previously only observed innanoscopic particles. By coupling optical,
mechanical and microwave electricalsignals, Cleland and Awschalom could
bring us closer to high-speed quantum
communications and long-term storageof quantum information.
“The diversity and breadth of subjects
covered at the workshop are an asset toour understanding and utilization ofmaterials and phenomena at the nanoand molecular scale,” says Ohno fromthe AIMR. “I am fully convinced that
this and following meetings will lead
us to new directions and discoveries.”
Ohno’s confidence is reinforced by thetangible successes that the AIMR has
thus far achieved through its joint research centers, whether in Santa Barbara,
Cambridge or Beijing.

35

IN THE SPOTLIGHT

TOP-LEVEL INTERVIEW

Published online on 27 October 2014

The AIMR’s reforms positively
impact Tohoku University
The various reforms introduced by the AIMR have assisted Tohoku University in its quest to become aworld-leading university

S

ince its establishment in 2007 as a
research institute in the Japanese
government’s prestigious World
Premier International Research Center
Initiative (WPI), the AIMR has undertaken several reforms, which have helped
it become one of the world’s leading materials research institutes. Tohoku University
is very appreciative of the AIMR’s
efforts and is now adopting the AIMR’s
reforms to help it make a further leap
forward. President of Tohoku University,
Susumu Satomi, and AIMR Director
Motoko Kotani discuss the outcomes ofthese reforms and their impact on thewhole university as well as the future expectations of the university for the AIMR.
Effect of system reforms
Satomi: Since its establishment, ouruniversity’s philosophy has always been
to put research first, to maintain an
open-door policy, and to emphasize
practice-oriented research and education. As academia becomes increasingly
global, Tohoku University needs to flexibly
reform systems while maintaining ourlong-standing tradition in a bid to becomea world-leading university. Since being
appointed president in 2012, I have set
two goals, namely achieving world-classstatus and spearheading the restorationof Tohoku and Japan after the Great
East Japan Earthquake in March 2011.
I announced the seven-point “Satomi
Vision” to achieve these goals, whichstresses the importance of system reforms.
Kotani: First, I would like to mention the
introduction of a top-down system for

36

AIMR Director Motoko Kotani (right) and the president of Tohoku University, Susumu Satomi (left), discuss the
positive benefits that the AIMR reforms have had on the university.

making decisions. Unlike most Japanese
universities, where decisions are generally
made at faculty meetings, in the AIMR
the director can make decisions at hisor her discretion, enabling the instituteto respond flexibly and rapidly. Sincebeing appointed director in 2012, I havebeen trying to achieve breakthroughs
by promoting collaborations between
researchers in the fields of mathematics
and materials. We are already seeing
accelerated integration of different
research fields and benefits over a shorttimescale as a result of this top-down
decision making.
I also want to stress the reforms to
the administrative division. In the past,
I found it difficult to implement reforms
due to red tape. But the AIMR’s administrative staff strongly desire to change
the university, and they conduct theirown work while implementing necessaryreforms and supporting researchers.
They established their own systems for
inviting foreign researchers and organizing international symposiums, which
had previously been done by researchers.
This enables us to operate smoothly as aninternational research institute.
Satomi: In July 2014, Tohoku University
set up the Organization for Advanced
Studies (OAS), which will promote theinternationalization of the university andits world-class advanced research. We plan
to make the AIMR the first member of
the OAS, and then allow other institutes
to join. Furthermore, we will create a
research reception center at the OAS bytaking advantage of the knowledge that
the AIMR has accumulated. The establishment of the OAS is the biggest outcomethat the AIMR’s reforms have brought toour university.

AIMResearch 2014

IN THE SPOTLIGHT

Kotani: Thank you very much. I am very
gratified to know that our efforts havebrought concrete outcomes and havecontributed to the further development of
the university.
Reforms to personnel regulations
Kotani: One of the AIMR’s missions as
a WPI research institute was to recruit
outstanding researchers from around theworld. To achieve this, we had to offer
high levels of compensation. In light of
the intensifying global competition in
recruiting researchers, I felt strongly that
we would be unable to conduct top-levelresearch and attract excellent researchersand students unless we provided themwith more incentives than previously.
The AIMR first established a meritbased pay system based on annual appraisals and achievements of researchersin an effort to raise their motivation levels.
AIMR researchers can negotiate all sortsof conditions, including payment andresearch environment. I think that thissystem is one reason why the AIMR is
successful. We have also introduced a joint
appointment system, in which excellent
researchers affiliated with other departments at Tohoku University and otherinstitutions can concurrently serve as
principal investigators at the AIMR.

Satomi: Traditionally, Japanese universities have not set salaries based on theachievements of researchers. Tohoku
University has introduced a distinguishedprofessor system modeled on the AIMR’s
pay system; it allows high-level professors to receive salary bonuses. Tohoku
University must lead other universities bytaking advantage of the joint appointment
system. We have formed a project team to
discuss how to become a hub of the global
circulation of talented researchers.
Provision of English research support
Kotani: Providing research support
in English was another importantmission as a WPI research institute.
This was mostly realized in the earlystages of establishing the AIMR. Over90 per cent of our administrative staff
can speak Japanese and English, anddaily announcements and information
about grant applications are provided
in both languages. In addition, we haveestablished a system that allows all
researchers, including non-Japanese
speakers, to easily perform various administrative procedures.
One reform I have undertaken since
becoming director was establishing the
Research Support Center. The center provides fundamental analytical equipmentthat is used by most researchers. Staff
with a PhD provide support in English,
allowing researchers to commence fully
fledged research immediately on arriving
at the AIMR.
Satomi: Administrative support in English
is also essential for Tohoku University to
become a truly international university,and I’m thankful to the AIMR for heralding the move. The impact is spreading
across the university as some of the
AIMR’s administrative staff have moved toother departments.

The Research Support Center provides analyticalequipment and English services to support researchers.

AIMResearch 2014

Kotani: We have recently started sharing
our administrative expertise with otherdepartments of the university. Examples
include secretarial manuals and examplesof emails when communicating with overseas research institutes and researchers.
We are doing our very best to contributeto the university.

The AIMR created a common space with the aim ofpromoting interaction between researchers.

Leaping ahead
Kotani: We have implemented manyother reforms in addition to those we havediscussed. For example, we have created acommon space that all of the AIMR staff
and researchers can use freely with theaim of fostering interaction between them.
Such an open atmosphere was difficult toestablish when traditional Japanese culture
prevailed, but we consider it to be an essential element for progressing research.
We use the space for various events, such
as Tea Time every Friday and researchpresentations and seminars by guest researchers to strengthen interactions. The
resulting connectivity has already proved
effective for driving collaborative research.
Satomi: Finally, I would like to mention
that, in addition to the system reforms,
the AIMR has also greatly contributed tothe university educationally. We are currently establishing a graduate schoolthat specializes in spintronics — anarea where Tohoku University leads theworld — thanks to the advanced researchat the AIMR and the global connections of
its researchers. I am very grateful for that.
By actively adopting successful reforms of
the AIMR, Tohoku University will continue to become a world-class university andfunction as a hub for international talent.

37

IN THE SPOTLIGHT

INTERNATIONAL WORKSHOP

Published online on 26 January 2015

Reinforcing a strong andfruitful friendship
The third workshop jointly organized by the AIMR and the University of Cambridge reinforced the two institutes’
longstanding partnershipIn early December, the Advanced
Institute for Materials Research (AIMR)
and the University of Cambridge held ajoint workshop in the UK to share their latest discoveries, encourage student exchange
and reinforce longstanding partnerships.
The event saw presentations on the catalyzing properties of sponge-like nanoporous
gold, explorations into the atomic landscapeof perovskites and a mathematician’s takeon materials science.
On the morning of December 9,
Susumu Satomi, president of Tohoku
University, and Jeremy Sanders,
pro-vice-chancellor for institutional
affairs at the University of Cambridge,
signed a declaration of intent to deepen
academic and research collaboration
between the two universities. The signingceremony was attended by AIMR Director
Motoko Kotani together with a representative from the Embassy of Japan in the UK
and several professors with expertise in theareas of global safety and materials science.
More than 40 individuals were present forthe program.
The two universities established an
AIMR Joint Center (AJC) back in 2012.
“In the few years that the center has been
operational, it has really developed into a
focal point for promoting and strengthening AIMR’s presence in Cambridge,” says
Katherine Orchard, a researcher at the AJC
who spends most of her time in Erwin
Reisner’s laboratory at the Department ofChemistry in Cambridge. Orchard is focusing on the development of nanostructured
materials that can absorb solar energy andtheir use to split water into its constituent
elements, hydrogen and oxygen, ultimately
paving the way for hydrogen-powered38

Naoki Asao, a professor at the AIMR, presented his work on nanoporous gold at the third annual AIMR–Universityof Cambridge joint workshop.

vehicles and electrical devices. “Both the
University of Cambridge and the AIMR arerecognized as world-class institutions andknowledge transfer between the two can
only lead to better research,” she adds.
On the day after the official signingceremony, Orchard joined more than
50 students and researchers at the workshop on December 10 to listen to plenary
lectures and discuss the latest trends andcontroversies in areas such as metallurgy,
spintronics and topological insulators.
A parallel session was held to discuss
opportunities for student and researchexchange between the AIMR and the
University of Cambridge. Representing

the AIMR, Administrative Director
Masaru Tsukada delivered a presentationon the Global Intellectual Incubation andIntegration Laboratory (GI3 Lab), a uniqueresearch exchange program in which
excellent young researchers are brought to
Sendai and hosted at the AIMR for one tothree months.
Catalyzing effects
Among the presenters at the scientificsessions was Naoki Asao, a professor at the
AIMR who has previously collaborated
with Reisner’s laboratory in the development of water-splitting systems. Asaoshared his work on the use of nanoporous

AIMResearch 2014

IN THE SPOTLIGHT

Over 50 students and researchers attended the joint workshop to listen to talks on various subjects, including the presentation on batteries and supercapacitors by Clare Grey,a professor at the University of Cambridge’s Department of Chemistry.

gold for novel, selective chemical transformations, resulting in the production of avariety of valuable organic molecules in amore environmentally sustainable way thanexisting methods.
Almost a quarter of a century ago,scientists discovered that the synthesis ofnanosized particles of gold transformed
the catalytically inert metal into aremarkable agent for change. However,these nanoparticles tend to huddle back
together into larger particles, losing theircatalytic powers. Now, Asao and his colleagues have discovered that nanoporous
gold materials, riddled with tiny holes

between 10 and 50 nanometers in diameter, have durable structures and highcatalytic activity and can be recovered forreuse, thus making them ideal catalysts forsynthetic chemistry.
In another presentation, Taro Hitosugi,
an associate professor in the AIMR
Materials Physics Group, elaborated on
the use of scanning tunneling microscopy
to closely observe oxide thin films withperovskite structures and potentially engineer their growth, atom by atom. Thesematerials exhibit the fascinating propertiesof high-temperature superconductivity
and magnetoresistance.

Mathematician and professor at the AIMR, Yasumasa Nishiura, was invited to speak on the happy union between
mathematics and materials science.

AIMResearch 2014

Mathematician and professor at the
AIMR, Yasumasa Nishiura, reminded
the audience of the historical rapport
between representatives in the fields ofmathematics and materials science. He
went on to elaborate on the potential
for mathematics to describe amorphousmaterials that lack a repetitive atomic
structure, such as glass, for which no reliable model exists.
To further foster the close relationship between these two fields of intellectual endeavor, Nishiura’s Mathematics
Unit has set up a research group withthe experimental laboratories of Lindsay
Greer at the University of Cambridge
and Tadafumi Adschiri at the AIMR
and is beginning to extend these links tomathematics departments at Cambridge.
“Today’s scientific activities are becoming
more and more borderless,” says Nishiura,“and consequently, joint research centers
are important to support the exchange
of information and people, especially fortheoretical sciences like mathematics.”“The success of the workshop at
Cambridge proved that the AIMR Joint
Research Center is an important asset
for advancing research in the field,” says
a pleased Kotani. “I am happy that these
efforts helped to strengthen the relationship between Tohoku University and the
University of Cambridge and anticipate
further acceleration in research and moreinternational recognition.”

39

Advanced Institute for Materials Research
Tohoku University