A chievements of ICYS Research Fellows
New strategies for the development
of blood-compatible materials
Caterina Minelli
PhD at Centre Suisse dElectronique
et de Microtechnique (CSEM) ( Switzerland),2004. ICYS Research Fellow
since 2005.
Nowadays, synthetic
materials that interface
blood are widely used in
medicine, both for
devices such as catheters and for replacing
diseased parts of our
body. Unfortunately,
ideal materials exhibiting
a perfect compatibility with our body
have not been able to develop, especially in long-term performances. The
use of synthetic materials, thus, must
be supported by anti-coagulating
drugs. Most of the current methods
used to improve the compatibility of a
material with blood consist in the
chemical modification of the surface.
A large variety of techniques have
been investigated, however the performances of these materials are still
not optimal.
In NIMS/ICYS, to improve the compatibility of materials with blood, we
are focusing our attention on the
shape of the interface between the
materials and the blood. As soon as
the blood contacts an artificial material, the proteins start to adsorb onto
the material surface and change their
conformation. Thus, the platelets
interact with these and eventually
start adhering and spreading onto
the protein layer. The platelets in this
state are activated to release blood
coagulation factors. All these events
initiate the formation of thrombi.
We are trying to understand if it is
possible to shape the materials surface in order to control the protein
adsorption or the platelet spreading.
This would mean controlling thrombus formation. Plasma proteins have
different dimension and different
shapes, but their typical sizes range
from the nanometer to the submicrometer scale. Blood cells can
vary their size from few micrometers
as in the case of platelets, up to 15?
μm for some white cells. The kind of
structures we investigated, then, have
typical feature sizes from the nanometer to the micrometer length-scale.
Moreover, we worked with polymers
as this class of materials can be
selected to be biocompatible and
biodegradable, can be structured
using simple methods and can be
used to coat a large variety of substrates.
We could demonstrate that both protein adsorption and platelet behavior
are influenced by the topography at
the surface. The dimension of the
features at the interface may influence, for example, the orientation of
the proteins adsorbing onto the
material surface. Also, platelet adhesion and spreading onto the films
could be controlled varying the
aspect ratio of the features.
These findings will be used to tailor
the surface properties of novel materials used, for example, in vascular
applications. Chemical and topographical attributes will be combined
synergistically to produce highly
blood compatible materials, which
minimize the possibility of thrombus
formation and thus reduce health risk
factor for the patients.
Yoshihiro Takahashi
(specializing in energy/environmental engineering)
ICYS research fellow since 2004
Glass and crystal materials are essential
materials for photonics. There is an
urgent need to develop advanced
active materials for a light-wave control
device in line with the rapid development of the information society. In
ICYS, I am doing research mainly focusing on searching and synthesis of new
optical glass and illuminant materials
for a photonic device.
It has been believed so far that glass
6 melting pot No.8 November 2006
materials merely transmit
light just as optical fiber
transmits optical signal and
will not have any function, in
principle, like wavelength
conversion. I have been
working on developing new
glass materials with an
added permanent optical functionality
by using a phenomenon of crystallization .
The following shows part of my
research at ICYS.
Fig. 1 shows transparent crystallized
glass created. I have confirmed both (a)
large second harmonic generation and
(b) white fluorescent light. There has
been no report on any material which
produces these two functions at the
same time. Furthermore, it was found
Fig. 1 Wavelength conversion through nano-crystallized glass
Fig. 2 New orange phosphor in titanate
The World First Fabrication of Single-Crystalline
Mg3N2 Nanowires Junqing Hu
ICYS Research Fellow since 2004
Platelets on nanostructures: Platelets adhering on the channel walls
of the micro-fluidic chip. They assume a different morphology
depending on what kind of feature the interface presents.
rescent material
(BaTiSi 2 O 7 ). I have confirmed the projection of
clear orange luminescence
by ultraviolet excitation.
The color of fluorescence
with titanate crystal
reported so far is
blue/green, and this report
is the first case of orange
color. The luminous phenomenon of titanate crystal has a great deal of
unknown part. I think
BaTiSi2 O7 found to produce orange color luminescence is a very important
material not only as fluorescent material but also
as a target of elucidating a
luminous phenomenon.
Carbon Nanotube New Application
MS in Materials Science at Harbin Institute of Technology,
PhD in Chemistry at University of Science ? Technology
of China, Senior Assistant Researcher, City University of
Hong Kong (2000) and JSPS Post-Doctoral Fellow (2002).
Development of titanate crystal
glass with optical functionality
PhD at Nagaoka University of Technology, 2003
that this material consists of fine crystals of several hundred nm. Oxide glass
showing nano-crystallization of optical
functionality crystal is needed as optical application materials of next generation. I think that this material found
in this research has a great potential as
a new nano-photonics device forming
cyclical optical functionality crystal of
nanometer size.
In general, fluorescent materials have
rare-earth elements as Ce3+: Y3Al5O12
and Eu2+: BaMgAl10O17. But, these are
produced in a few limited countries
only. Therefore, elements like Eu, in
particular, are very expensive. In the
meantime, study is carried out on luminescence property of several titanate
materials, but many of them do not
show luminescence at room temperature. Fig. 2 shows a novel titanate fluo
We have developed carbon nanotubes
(CNTs) as nanoreactors for the first
fabrication of single-crystalline Mg3N2
nanowires, and have systematically
analyzed the Mg3N2 nanomaterial by
transmission electron microscopy
(TEM), high-resolution TEM and electron diffraction.
Magnesium nitride, Mg3N2, known also
for some other alkaline rare-earth
metal (M3N2, M = Be, Mg, Ca) nitrides,
is a direct energy gap semiconductor
(~ 2.8 eV), and may serve as a potential
high-temperature semiconducting
material and/or component of a semiconductor heterostructure useful in
nanoelectronics. Due to fast decomposition of Mg3 N2 in the presence of
water in the atmosphere, the synthesis
of single-crystalline Mg3N2 nanowires
has not yet been accomplished and
remains a challenge.
Due to the characteristic
internal cavity, CNTs can
serve as nanoreactors for
introducing reactive species
and reactants, followed by
desired reactions with an
aim to produce nanowires in the confined configurations. The resulted
products are homogeneously sheathed
with graphitic carbon tubular layers,
which effectively prevent the decomposition of as-synthesized nanowires (see
Figure).
The formation of single-crystalline
Mg3N2 nanowires sheathed with CNTs
proceeds via a simple thermal reaction
process using MgB2, Ga2O3, activated
carbon powders, and N2 as source
materials. The reaction of Ga2O3 and
activated carbon at a processing temperature (-1200℃) in a N2 flow
resulted in the CNT growth via a Gacatalyzed vapor-liquid-solid process. In
the growth process of Mg3N2 nanowire, as-formed CNT acts as a reactor.
Figure (A)
TEM images showing that Mg3N2
nanowires have a uniform diameter
along the length. The inset depicts the
ED pattern of this wire.
(B)
High-magnification TEM image showing
a uniform and thin carbon sheath on a
Mg3N2 nanowire.
(C)
HRTEM image taken from the interface
domains between a Mg3N2 nanowire
and a C-coating.
The reactive species including Mg
vapor and N2 are then transported
by carrier gas (N2) and enter the
CNT to produce Mg3N2 nucleus, and
the CNT will confine the 1D nanowire
growth inside the tube.
Extensive HRTEM and electron
diffraction examinations indicate the
Mg 3 N 2 nanowires are structurally
uniform single-crystalline, and the
nanowires grow along one of four
possible orientations, i.e. the [001],
[011], [111], and [112] crystallographic directions of the Mg 3 N 2
single crystal.
Fabrication of carbon layer stably
preserving Mg 3 N 2 nanowires may
promote further experimental studies
on their properties and crystal structures (the first microstructure studies
using TEM technique on this material
herein). The developed CNT as
nanoreactor method might be useful
for the formation of protective
carbon coatings on the III-V and II-VI
semiconductor nanowires in order to
prevent their surface oxidation
and/or hydrogenation.
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