The 4th NIMS--MPI-MF Workshop

Supported by International Affairs & Public Relations Office of NIMS

National Institute for Materials Science, Namiki site, Japan

July 6-7, 2006

Organizing Members: NIMS side : Dr. Yutaka Wakayama, Dr. Seiichi Takami Dr. Michiko Yoshitake Dr. Takahiro Nagata Dr. Naoto Umezawa Dr. Kenji Ohmori Dr. Masamitsu Haemori Dr. Dmitry Kukurznyak Dr. Ryoma Hayakawa Dr. Chisato Niikura Dr. Toyohiro Chikyow Dr. Hiroyuki Kobayashi Dr. Tetsuya Tateishi Dr. Hisao Kanda Secretary office : Ms. Hiroko Inoue Ms. Yumi Hirose Ms. Rieko Aizawa MPI-MF side: Dr.Gunther Richer Dr. Seigfreid Hofmann Prof. Helmut Dosch

Preface

It is our great pleasure to organize the 4th NIMS- MPI-MF Workshop at NIMS

campus in Tsukuba Science City in Japan.

The Max Plank Institute for Metals Research is the first Institute overseas that NIMS

made the comprehensive research agreement. We have had an introductory visit and some

workshops so far. In fact a lot of collaboration has been done and most of them are still going.

Now, we are in the season of getting harvest of this collaboration. We can find some other

seeds of collaboration under this research scheme. In this workshop, we have decided to show

the on-going collaboration and the potential collaboration which has been performed between

NIMS and MPI. We hope the research topics in this workshop can provide us with some hints

to start the future collaboration.

Finally, we would like to appreciate all the researchers and administrative staffs who

made efforts in making this comprehensive research agreement and organizing this workshop

at NIMS.

Prof. Teruo Kishi, President,

National Institute for Materials Science.

Hotel and Workshop site information 1) Access from Narita (Tokyo ) International Airport to Tsukuba

About Hotel : Okura Frontier Hotel Tsukuba Epocal :

Bus time table from Narita to Tsukuba

NIMS Campus

Tsukuba Bus Center

Hotel: Okura Frontier Hotel Epocal :

Workshop site: NIMS Namiki Campus

N H

East Blvd.)

South

The 4th NIMS – MPI-MF Workshop NIMS Namiki site , Japan

July 6-7, 2006

Agenda Thirsday July 6, 2006

- Opening - 13:00 Opening remarks T.Kishi ( NIMS) Future of NIMS / MPI-MF – collaboration

on material science

13:15 Expectation for the future collaboration Prof. Dosch (MPI-MF)

between MPI-MF and NIMS

- Ongoing collaboration I: Thin film growth and characterization -

Chair person: Y. Wakayama 13:30 Hidden seeds for NIMS-MPI collaboration T. Chikyow (NIMS)

in the modern LSI research front 14:00 High Energy X-rays in Materials Science H. Reichert (MPI-MF) 14:30 Epitaxial oxides on Si D.Kukurznyak (NIMS) 15:00 Crack propagation in nanocrystalline Al films G. Richter (MPI-MF)

observed by in-situ transmission electron microscopy

15:30 Lab. Tours ( Namiki site )

17:30 Banquet at Namiki site

Friday July 7 , 2006

- Topics for potential collaboration I: Thin film growth and characterization -

Chair person: H. Reichert 09:00 Mechanical properties of ultra thin metallic films P. Gruber (MPI-MF)

– Plasticity and fracture of Cu/Ta film systems 09:30 In-situ epitaxial growth and characterization of M. Yoshitake (NIMS)

atomically flat epitaxial alumina films

10:00 Epitaxy of Ga-nitrides on transparent and E.G. Víllora (NIMS) conductive β-Ga2O3 substrates

10:30 Coffee break

- Ongoing collaboration II: Molecular assembly and functions –

Chair person: N. Hosoda 11:00 Growth of nanostructured molecular assemblies Y.Wakayama (NIMS)

11:30 Self-assembly of 2D binary organic layers E. Barrena (MPI-MF) 12:00 Wireless information transport on organic monolayer A. Bandyopadhyay (NIMS) 12:30 Lunch

- Topics for potential collaboration II: Biomaterials -

Chair person: R. Kemkemer 14:00 Biocompatible nano-materials application H.Kobayashi (NIMS) to tissue engineering scaffolds

14:30 Towards selective neuronal adhesion on bio F. Corbellini,(MPI-MF)

functionalized nano patterned hydro gels

15:00 Quantitative method for the analysis of cell attachment Furong Tian (NIMS)

using the aligned scaffold structures

15:30 Coffee break

Chair person: T. Chikyow

16:00 An in situ Laboratory for Sample Preparation and Testing S. Orso (MPI-MF) of Materials and Structures at the Micrometer Scale

16:30 Biomimetic Approach to Reversible Interconnection N. Hosoda (NIMS)

17:00 Dynamics of cell alignment and altered morphology R. Kemkemer (MPI-MF) induced by cyclically stretched substrates

- Closing -

17:30 Closing Remarks H.Kanda (NIMS) 17:45 Closing Remarks next MPI-MF-NIMS WS Prof. Spatz (MPI-MF) 18:00 Departure from NIMS Namiki site

Hidden seeds for NIMS-MPI collaboration in the modern LSI research front

T. Chikyow1,2 ,D.Kukurznyak,K.Ohmori1, T.Nagata1, N.Umezawa, and K. Nakajima1, G. Richter3 H. Reichert3 T. Wagner3 andH.Dosch3

1 Nanomaterials Laboratory, National Institute for Materials Science, Tsukuba, Japan,

2 CREST-Japan Science and Technology Corporation, Japan 3 Max Plank Institute, Research Institute for Metal Research

* E-mail:CHIKYO.toyohiro@nims.go.jp

Due to the scaling down of the transistors, the practical gate stack materials are composed of nano materials and atomic scale understanding are required to control the nano interfaces..

In future 45 nm or less gate node generation, the gate oxide will be HfO2 based oxide in a few nm thick and the gate material will be expected to be metal alloys, including metal nitrides.

A critical issues in gate stack structure are 1) how we can make stable oxide on Si substrate , 2) how to control the work function to give a precise Vth in MOSFET and 3) how to avoid the Fermi level pinning at metal/gate oxide interface. Here the fundamental and critical structures are the oxide/Si interface and metal/oxide interface, which has been studied in NIMS and MPI.

At the oxide/Si interface, the SiO2 is normally formed at the interface and from the requirement

of higher dielectric property, elimination of SiO2 is preferable. To make the direct contact of oxide to Si, thermodynamic idea is applied to form SiO2 complex at the interface. Here the reaction of oxide with Si and thermal stability of oxide/Si interface must be considered thermodynamically. To estimate the interface structure in nano scale, the high resolution transmission electron microscopy or surface analysis has been the powerful tool but in some case, the required issues are almost beyond the detection limits of this characterization tool. We need new idea to imagine how the interface is.

At the metal/oxide interface, the situations are so complex and a lot of experiments and understanding are needed to accumulate the knowledge of this interface. First of all, the reaction of metal with oxides must be taken care and electrical structures, which are typically characterized by XPS, is the inevitable method. Also at the metal/oxide interface, Fermi level pining occurs and Work Function dependence sometimes is not observed or it is quite small though we can see the dependence.

The combinatorial synthesis and some high-throughput characterization were found to be quite

effective and we have been working together using unique tools at NIMS. In this talk, we summarized our past activities in collaboration and show some seeds for NIMS and MPI collaborations.

< Note and Memo >

High Energy X-rays in Materials Science H. Reichert Max-Planck Institute for Metals Research, Stuttgart, Germany Abstract

We have developed dedicated experimental stations at the European Synchrotron Radiation Facility (ESRF, Grenoble, France) in order to exploit the potential of high energy x-rays for a wide range of materials science applications. The particular properties of high energy x-rays allow us to perform structural studies on bulk samples as well on thin film systems or nanostructures. In addition, high energy x-rays are an ideal probe for deeply buried structures.

We will present the results of a number of case studies, in particular on water/ice structures at hydrophobic/hydrophilic interfaces. The high spatial resolution available with our instruments allow us to study water depletion layers at such interfaces with unprecedented resolution. Other examples, concerning the structure of liquid metals at a variety of interfaces such as semiconductors and insulators, reveal the existence of new phenomena at solid-liquid Schottky on a nanoscale.

< Note and Memo >

Epitaxial apatites on silicon

Dmitry Kukuruznyak1, Kenji Ohmori1, Harald Reichert2, and Toyohiro Chikyow1 Affiliation: (1) National Institute For Materials Science

Advanced Electronic Materials Center Advanced Device Materials group

1-1, Namiki, Tsukuba, Ibarakim 305-0044, Japan

(2) Max-Planck-Institut für Metallforschung Heisenbergstr.1

D-70569 Stuttgart +49 711 689 1927

E-mail: Dmitry.Kukuruznyak@nims.go.jp

reichert@dxray.mpi-stuttgart.mpg.de CHIKYO.Toyohiro@nims.go.jp

Controlling chemical reactions at the interface between two solids is a fundamental challenge. For example, high-dielectric-constant (high-k) oxides which must be used in future field effect transistors oxidize silicon during chip fabrication (at ~1030°C). The product of this reaction precipitates at the boundary as a thin SiO2 or silicate layer. The present straightforward approach comes to attempts to find a “thermodynamically stable” oxide or introducing diffusion barriers. However, at high temperatures no oxide is completely inert on silicon and it is very difficult to entirely eliminate diffusion. Here we report the discovery of a new class of oxides which quickly react with silicon at 1000°C and simultaneously sponge up the reaction products while retaining the precipitate-free interface and epitaxial connection with the substrate. The new dielectrics (k ≅ 26) are rare earth aluminum-silicon apatites Re6(AlO3)5(SiO3.5) with hexagonal crystal structure. They were obtained from the ReO1.5·5AlO1.5 precursors after rapid thermal annealing in slightly reducing atmosphere. Apatite thin films had mosaic-like morphology, with epitaxial orientation of the grains Apatite(140)||Si(001). Our result is an experimental proof that the interfacial inviolability can be achieved not by avoiding reactions and preventing diffusion, but by adjusting these two phenomena and using them together. We anticipate that the discovery of the first material, which exhibits the unique diffusion patterns, will stimulate development of the new alternative direction in silicon interface science.

< Note and Memo >

Crack propagation in nanocrystalline Al films observed by in-situ transmission electron microscopy G. Richter1, T, Saif2, E. Arzt1

1Max-Planck-Institut für Metallforschung, Stuttgart, Germany 2Universiy of Illinois, Urbana, USA Nano crystalline metal structures are of interest for micro electronics and micro/nano mechanical systems where they are subjected to thermo-mechanical loading. There are two fundamental questions related to their mechanical reliability: their deformation mechanism, and their failure mechanism. We studied the behavior of freestanding fcc metal films loaded uniaxially in an in-situ straining stage in a transmission electron microscope (TEM). Al (99.99 % purity) was magnetron sputtered deposited as a 100 nm thick layer on Si wafers under high vacuum (1·10-7 mbar base pressure) conditions. Subsequently MEMS structures were fabricated from the thin film system. The MEMS process provides a defined 100 x 10 µm2 freestanding film with a constant 100 nm thickness. The average grain size of the Al film was about 50 nm. The MEMS structure was taken to a TEM (AEI-EM7) operated at 1000 kV; for this microscope we employ a tensile testing holder which operates at room temperature. The specimen was strained in steps to study its response under stress. No dislocation movement was observable in the grain interiors during straining steps. Instead crack formation and propagation was observed. Eventually two main cracks formed, one close to the Si-support, the other from an edge imperfection in the freestanding film. The crack tip and the region ahead were monitored and recorded by a TV-CCD camera to investigate the mechanisms of crack propagation. The crack advances by generating multiple micro cracks ahead of the crack tip; the main crack advances by coalescence of these micro cracks. The crack propagates entirely in an intergranular manner, suggesting that nano crystalline metal films initiate failure primarily by grain boundary separation under load. Also dislocation nucleation and movement was studied in the region ahead the crack tip. No dislocation movement is observed in small grains (<50 nm diameter) whereas the bigger grains with a diameter of about 200 nm dislocation movement during straining is reproducibly observable. Both observations, the intergaranular crack propagation and the absence of dislocation nucleation or movement in the small grains indicate that nano crystalline films become brittle and fail primarily by grain boundary separation.

< Note and Memo >

Mechanical properties of ultra thin metallic films – Plasticity and fracture of Cu/Ta film systems P. Gruber 1, J. Böhm 2, R. Spolenak 3, A. Wanner 4 und E. Arzt 1,5 1 Universität Stuttgart, Institut für Metallkunde, Stuttgart, Deutschland 2 Robert Bosch GmbH, Stuttgart-Feuerbach, Deutschland 3 ETH Zürich, Labor für Nanometallurgie, Departement Materialwissenschaft, Zürich, Schweiz 4 Universität Karlsruhe, Institut für Werkstoffkunde I, Karlsruhe, Deutschland 5 Max-Planck-Institut für Metallforschung, Stuttgart, Deutschland Although it is well known that thin films exhibit mechanical properties very different from those of their bulk counterparts, knowledge of the underlying mechanisms is incomplete. A prerequisite for getting more insight into the deformation mechanisms of ultra thin films is to be able to control different testing parameters independently. Here we utilize a novel synchrotron-based X-ray diffraction technique, with which it is possible to characterize the evolution of stresses in ultra thin polycrystalline metallic films on compliant substrates during isothermal tensile tests. Thus, in contrast to thermal cycling experiments stress and temperature can be decoupled during the experiment and the films can be tested up to higher total strains. Different Cu film systems with and without Ta capping and/or interlayer on compliant polyimide substrates have been tested up to total strains between 3 and 8%. The measurements reveal a distinct size effect on flow stress as well as cracking behavior. The flow stress for all Cu film systems increases with decreasing film thickness, nevertheless the influence of the different interfaces is much smaller than expected. On the other hand the very high strength of the thinnest films leads to a distinct reduction of ductility in the Cu films since samples with a Cu film thickness below 300 nm and at least one Ta layer show brittle fracture at a total strain of about 2.5% whereas similar samples with a Cu film thickness above 300 nm show plastic deformation up to total strains of 8%. Both size effects will be critically discussed with respect to current models of thin film plasticity and fracture mechanics of thin films on substrates.

< Note and Memo >

In-situ epitaxial growth and characterization of atomically flat epitaxial alumina films

Michiko Yoshitake, Weijie Song, Yaroslava Lykhach, Slavomir Nemsak

National Institute for Materials Science E-mail: yoshitake.michiko@nims.go.jp

The growth and characterization of atomically flat ultra-thin epitaxial alumina films on NiAl(110) and on Cu-9Al(111) was achieved by selective oxidation in ultra-high vacuum. The growth process, crystal structure, interface, chemical states and so forth were characterized in-situ by low energy electron diffraction (LEED), reflection high energy electron diffraction (RHEED), X-ray photoelectron spectroscopy (XPS), ultra-violet photoelectron spectroscopy (UPS). By oxidizing under appropriate condition, epitaxial alumina films (1-4 nm thick) grew on both alloys. It was confirmed that the alumina films were atomically flat by RHEED patterns, which are shown below. The streaky patterns in the photos are characteristic for two-dimensional growth.

substrate

aluminasubstrate alumina

Al2O3/NiAl(110) Al2O3/Cu-9Al(111)

Layer-by-layer growth

Selective oxidation Deposition & oxidation

3-D growth = roughAl

RHEED patterns from alumina/NiAl(110) and alumina/Cu-9Al(111) and schematic representation of the mechanism of atomically flat alumina growth.

< Note and Memo >

Epitaxy of Ga-nitrides on transparent and conductive β-Ga2O3 substrates

E.G. Víllora1, K. Shimamura1, Kazuo Aoki2, K. Kitamura1

1NIMS, 1-1 Namiki, Tsukuba, 305-0044 Japan, 2Koha Co. Ltd. villora.garcia@nims.go.jp

β-Ga2O3 is the most transparent

conductive oxide, with a bandgap of 4.8 eV. It compromises the visible transparency of sapphire with the electrical conductivity of SiC, which are the most widely used substrates for the growth of Ga-nitrides. Figure 1 shows the absorption edge at 260 nm and the free carrier absorption in the IR of a 1 in. wafer. We have demonstrated the growth of large-size single crystals, the processing to 1 in. polished wafers and the use of these for efficient light-emitting diodes based on the Ga-nitride system.

The difference in crystal structure

between gallium nitrides and β-Ga2O3 represents a fundamental problem for the epitaxial growth. An effective surface reconstruction of the a-plane β-Ga2O3, from two- to six-fold symmetry, is achieved for NH3 pressures ≥ 103 Pa, as shown in Fig. 2 by reflection high-energy electron diffraction (RHEED). The epitaxial growth of wurtzite GaN is evidenced by standard XRD and GIIXD measurements.

Present work shows the potential of β- Ga2O3

as an unique transparent and conductive substrate for future semiconductor technologies, in particular for devices requiring large current densities.

Fig. 1. Transmittance and reflectance spectrum of a 1 in. β-Ga2O3 wafer (shown in the inset).

Fig. 2. RHEED along [0 1 0] and [0 0 1] β-Ga2O3 azimuths: substrate (up), after nitridation (middle), and GaN epilayer (down).

< Note and Memo >

Growth of nanostructured molecular assemblies

Y. Wakayama1, H. Sasaki1, T. Chikyow1, K. Kobayashi2

1 National Institute for Materials Science 2 Shizuoka University

E-mail: WAKAYAMA.Yutaka@nims.go.jp

Growth of highly π-stacking molecular assembly is essential to develop organic molecular devices,

because π-conjugation is required to improve optoelectronic functionalities. The main purpose of our study is to explore a growth technique of molecular assemblies with π-π stacking structures. In this talk, we will present molecular design for controlling crystal structure, nanostructure growth using vacuum techniques, and structure analysis by XRD, AFM.

π−π sta

cking

SCH3

SH3C

π −πstacking

π−π stackingπ−π stacking

1µm

Molecular nano-wires with π−π stacking structure grown on a surface treated Si substrate. Chalcogen atoms attached to the both sides of pentacene play an essential roll for molecular assembly.

π−π sta

cking

SCH3

SH3C

π −πstacking

π−π stackingπ−π stacking

1µm

Molecular nano-wires with π−π stacking structure grown on a surface treated Si substrate. Chalcogen atoms attached to the both sides of pentacene play an essential roll for molecular assembly.

π−π sta

cking

SCH3

SH3C

SCH3

SH3C

π −πstacking

π−π stackingπ−π stacking

1µm1µm

Molecular nano-wires with π−π stacking structure grown on a surface treated Si substrate. Chalcogen atoms attached to the both sides of pentacene play an essential roll for molecular assembly.

< Note and Memo >

Self-assembly of 2D binary organic layers

E. Barrena (a,c,d), D. G. de Oteyza (a), Y. Wakayama (b), A. Bandyopadhyay (c), H. Dosch (a,d)

(a) Max-Planck-Institut für Metallforschung, Heisenbergstr.3, 70569 Stuttgart, Germany (b) Nanomaterials Laboratory, National Institute for Materials Science 1-1 Namiki, Tsukuba 305-0044 Japan (c) International Center for Young Scientists, National Institute of Materials Science 1-1 Namiki, Tsukuba, Ibaraki-305-0044 (d) Institut für Theoretische und Angewandte Physik, Universität Stuttgart, 70550 Stuttgart, Germany The high application potential of the so-called “plastic electronics” has sparked a world-wide research activity in the controlled and tailored growth of organic thin films. Among the different explored materials, small aromatic molecules have been recognized as promising candidates for future applications, because they can be grown in films of high crystalline order, thus fulfilling one of the important requirements to obtain high charge carrier mobility. In this work we study the growth of highly ordered organic architectures based on heterostructures of fluorinated copper-phthalocyanines (F16CuPc), an air stable organic semiconductors showing n-type behaviour, and diindenoperylene (DIP), which shows preferentially p-type behavior. We report the formation of self-organized mixed monolayers of DIP and F16CuPc with very high degree of ordering. This binary system has been studied on Au(111) and Cu(111) as a function of the mixing ratio by Scanning Tunneling Microscopy.

< Note and Memo >

Wireless information transport on organic monolayer

Anirban Bandyopadhyay1*, Y. Wakayama, K. Miki

*1International Center for Young Scientists, National Institute of Material Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044 Japan.

2Nanoassembly Group, National Institute of Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044 Japan.

2Nanoarchitecture Group, National Institute of Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044 Japan.

Abstract: Our digital world is binary –processes data in terms of 0 and 1 but neuron like bio-systems processes data in multilevel way –in terms of 0, 1, 2, 3….. and so on. To realize such a multilevel switch (0, 1, 2, 3…n) in a single molecule we need to control molecular orbital transition between these levels which has not been realized yet. Once generated, we need to control transport of information through molecules even in atomic scale packing, where wiring is impossible. For this purpose we need an organic monolayer of multilevel molecular switches where multichannel connectivity is possible and control transport of information through the molecules even though decision making switches are in atomic distance apart. We have realized such a large flexible connectivity and information processing capabilities in a mono-molecular layer of a quinone derivative on gold (111). We have observed that a typical quinine dye DDQ (2,3-Dichloro-5,6-dicyano-1,4-benzoquinone) self-assembles on a atomic flat reconstructed gold (111) surface in a zig-zag pattern which we found to be extremely flexible towards surviving incredible memory density during transport and logical operation processes. But existence of natural communication and information exchange among these switching molecules is largely ignored -enormous possibility hidden in its structure remains unexplored. Several theories like Artificial Neural Network (ANN), artificial intelligence (AI) are developed in the last century but mostly CMOS based giant architectures are used to mimic a few of such basic principles. Prospect of these systems are fairly limited because information processing path is very well defined and connectivity is far less inferior to any biological systems. As an alternative option we have realized tuning molecular properties at picoscale and when it survives in ultra-dense packing then made wireless transport of information to the destination by weak interaction (weak forces of nature serves as connecting wire). As generation and transport occurred at a time, we created unique memory patterns in a controlled way and observed interaction between these patterns –given the fact that creation of new pattern by interaction is the key to many complex logical and computational features of bio-systems. By pattern manipulation DDQ monolayer can adapt with situation, organize information by itself, survive under faults -repair without any external help and realize decision making machines (cybernetics, artificial intelligence).

anirban.bandyo@rediffmail.com

< Note and Memo >

Biocompatible nano-materials application to tissue engineering scaffolds Hisatoshi Kobayashi

Biomaterials Center, National Institute for Materials Science. 1-1, Namiki, Tsukuba, Ibaraki 305-0044, JAPAN

KOBAYASHI.Hisatoshi@nims.go.jp

Various nano-materials, made from bioabsorbable and biocompatible polymers, are

promising the application to tissue engineering. In fact, nanofiber made from biodegradable polymer such as collagen, chitosan, polyglycolide, (PGA), polylactide (PLA) and their random copolymers have been reported. The compatibilities with various cells such as smooth muscle cells, human embryonic palatal mesenchymal cells, endothelial cells and neural stem cells were demonstrated. Considering that the material size and feature can substantially affect the morphology, functionality and cell-cell interactions of cells grown on ECM, cells showed good attachment and proliferation in micro and nano-structured materials. Moreover, it is degraded with cell or tissue growth and the shape is enhanced the permeability of the requirements and wastes compared with other shaped scaffolds.

Electrospinning method enabled to produce and create nanofibers. The fundamentals of this method are depended on the balance between polymer solution properties for example viscosity, conductivity and surface tension and applied electric potential, each condition for each polymer is optimized. We aim to developed the nanofibrous biomaterials by three different improved electrospinning methods and surface modification to give the functions such as the cell adhesion and cell proliferation and cell differentiation, and to develop the ideal biocompatible tissue engineering scaffolds. In this talk, recent topics will be discussed.

Acknowledgement: (A part of) This work is supported by Research Promotion Bureau, Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. under the contract No. 16-794

< Note and Memo >

TOWARDS SELECTIVE NEURONAL ADHESION ON BIOFUNCTIONALIZED NANOPATTERNED HYDROGELS

Francesca Corbellini, Sabine Rinck-Jahnke, Stefan Gräter, Joachim P. Spatz

Max Planck Institute for Metals Research, Heisenbergstraße 3, 70569, Stuttgart, Germany

University of Heidelberg, Department of Biophysical Chemistry, INF 253, 69120 Heidelberg, Germany

Cochlear implants are auditory prostheses that allow coding of acoustic information into electrical stimuli by aid of electrode arrays implanted into the cochlea. Although these implants are very promising, their effectiveness decreases with time due to fibrous encapsulation that isolates the prostheses from the nervous system. Therefore, development of strategies to improve the neuron-implant interface is required. Efforts to improve cell survival and integration have focused on biocompatible scaffolds that support neuronal cell growth and function while inhibiting fibrous growth. These include immobilization of extra cellular matrix proteins as well as specific cell-receptors at surfaces, thus enabling biomaterials to influence cell attachment, differentiation and eventually tissue organization. The aim of the present study is to develop a biocompatible surface for selective adhesion of neurons to be ultimately used as coating material in cochlear implants. The coating material, ideally, would preferentially attract neurons to the surface of the implant leading to a better integration of the entire implant in the host tissue. From nature we know that cells are sensitive to cues from their substratum i.e.: mechanical, chemical and structural cues. Moreover, several studies have demonstrated that neurons display a spreading preference for ‘soft’ materials. Using a novel technique, nano-patterned gold particles were transferred from a glass surface to a polymeric surface based on poly (ethylene glycol) (PEG) with nano-scale precision. The gold nano-particles were functionalized with cyclic RGDfK peptide, L1 cell adhesion molecule and IKVAV peptide. Cell adhesion and growth of fibroblasts (REF-52 WT) and neurons (PC12-27) on the different substrates was study. We observed that both mechanical and structural properties combined with opportune chemical functionalization influence the cell adhesion behavior.

< Note and Memo >

Quantitative method for the analysis of cell attachment using the aligned scaffold structures

Furong Tian1, Hossein Hosseinkhani2, Hisatoshi Kobayashi1,3

1Bio-functional materials research group, National Institute for Materials Science. 2International Center for Young Scientists (ICYS), National Institute for Materials Science (NIMS) 1-1, Namiki, Tsukuba-shi, Ibaraki 305-0044, Japan. 3Institute of Materials Engineering, Tokyo Medical and Dental University, Japan.

KOBAYASHI.Hisatoshi@nims.go.jp TIAN.Furong@nims.go.jp

The nano-scaffold provided advance condition and applied to many different types of implantable medical devices. However, the research are basic on the disordered no woven structure and high concentration aligned fibers which prohibited the real reason for mechanism of cell adhesion. There is no clear consensus regarding which method and processing variables are most relevant to study cell adhesion on the scaffold. To get precise diameter of scaffold for cell adhesion, it is necessary to set up a model, which can be used to study cell adhesion in different diameter and chemical composition. We develop a new quantitative method of cell attachment analysis using the aligned scaffold structure by electrospinning. We count the cell number and measure the length of cell on the separated aligned scaffold, which were fabricated by the different composition fibers on different diameters. The result shows the cell number on the fiber is related with cell concentration. Attach number of cell are much higher on nano-fiber than that to the other micro-fibers. There is bell shape relationship between cell adhesion and collagen composition among all of diameter fibers. The combination of mathematical modeling and experimental observation employed in this study allowed a comprehensive and cohere description of the cell model, for the purpose of controlling the cell adhesion. This method is helpful to find suitable diameter and collagen concentration for cell attach. Our result suggests that the 500nm diameter and concentration at 67% collagen can provide better cell adhesion. We could directly provide evident for nano-fiber with collagen as biomimetic materials towards achieving integration between cells and scaffolds for tissue engineering applications by using aligned scaffold. Acknowledgement This work is supported by Research Promotion Bureau (No.16-794), Ministry of Education,

Culture, Sports, Science and Technology (MEXT), Japan.

< Note and Memo >

An in situ Laboratory for Sample Preparation and Testing of Materials and Structures at the Micrometer Scale S. Orso1, U.G.K. Wegst1, G. Huber1, C. Eberl2, E. Arzt1

1Max-Planck-Institut für Metallforschung, Stuttgart, Germany 2now at Johns Hopkins University, Baltimore, USA We developed a novel method for the quantitative investigation of the three-dimensional structure and the mechanical properties of biological samples of micron diameters. This technique allows the micromechanical testing in bending and tension. It uses a Focussed Ion Beam system (FIB) as an in situ laboratory for structural investigations, sample preparation and sample fixation. Mechanical tests are carried out in situ in a FIB and a scanning electron microscope. Advantages of this method are that samples from larger objects can be prepared site-specifically using the FIB, and that testing in tension is possible without end effects due to gripping, since the samples are affixed by metal ‘tapes’ deposited using the FIB. Forces are measured with a piezoresistive Atomic Force Microscope tip attached to a micromanipulator for high precision positioning. The displacement is determined from micrographs taken during the test. The strength of the method is demonstrated on three applications. The first is the measurement of the Young’s modulus of spruce wood cell wall material. The others are devices for 'dry' and reversible adhesion found in the attachment systems on the feet of insects and geckos. They consist of thousands of setae of several tens to 100 micrometers in length and a few micrometers in diameter and thus their mechanical characterisation provides a challenge already during sample preparation. For the first time, the strength and Young’s modulus of individual setae of the hairy attachment systems of the beetle Gastrophysa viridula and the gecko gecko could be determined using this method.

< Note and Memo >

Biomimetic Approach to Reversible Interconnection

Naoe Hosoda

Advanced Nano Materials Laboratory, Interconnect Design Group, National Institute for Materials Science

1-1, Namiki, Tsukuba, Ibaraki 305-0044, JAPAN

E-mail: HOSODA.Naoe@nims.go.jp

Disassemblability of joints is an important requirement for environment- friendly products. The

most conventional metallurgical joining technologies were developed with importance placed only on high joint strength. Therefore the joined part is difficult to separate. The natural world offers valuable suggestions for this purpose. Especially, it is superior to have the mechanism of self destruction. Tree shed easily the leaves by an abscission layer, in case of need. Adhesive ability of insects such as flies and beetles is also interesting from a viewpoint of reversible interconnection. They can adhere on various surfaces and peel off quickly and reversibly.

In this workshop, we present our challenges of biomimetic joining technology using self destruction by abscission layer performed at NIMS and investigation about adhesive ability of insects on various surfaces performed as a cooperative research between MPI and NIMS.

< Note and Memo >

Dynamics of cell alignment and altered morphology induced by cyclically stretched substrates

Simon Jungbauera, Ralf Kemkemera, Huajian Gaoa,b

aMax-Planck-Institute for Metals Research, Stuttgart, Germany bBrown University, Providence, USA

Many cell types align perpendicular to the strain direction if cultured on a periodically stretched substrate. Although this type of cell alignment has been described extensively there are not many examination regarding the dynamics and frequency dependence of this response not to mention the exact mechanism behind that response. In the present work a stretching device was designed to allow live cell imaging by phase and high resolution fluorescence microscopy. We examined the dynamics of the cell motility, reorientation, morphology changes, and proliferation under various strain frequencies between 0.1 and 20 Hz. Human fibroblasts and REF cells were grown on deformable polydimethylsiloxane (PDMS) culture dishes coated with fibronectin. Time lapse movies were recorded during the experiments. We found that cell alignment started without significant lag time and increased exponentially with a characteristic time of approx. 100 minutes. This characteristic time does not depend on the stretching frequencies if f > 0.5 Hz but decreases with frequencies <0.5 Hz. Cell morphology changes in two stages: i) initial rounding up of the cell for approx. 40 minutes, than an elongation in direction perpendicular to the strain direction. Having stopped the stretching after 6 hours cells were further observed in order to determine the relaxation back to a random orientation. This occurred with a characteristic time of approx. 300 min and did not depend on the previous stretching frequency. The experiments allow determining deterministic parameters and the size of a noise source in a stochastic model for the cell response. Further experiments are done with GFP-fusion proteins to examine the dynamic response of the actin stress fibers and focal adhesions to elucidate the role of these structures in the cell response.

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