1
|
Ohira M, Nakagawa S, Sampei R, Noritomi T, Sakai T, Shibayama M, Li X. Effects of network junctions and defects on the crystallization of model poly(ethylene glycol) networks. SOFT MATTER 2023; 19:1653-1663. [PMID: 36756772 DOI: 10.1039/d2sm01036d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Polymer crystallization drastically changes the physical properties of polymeric materials. However, the crystallization in polymer networks has been little explored. This study investigated the crystallization behavior of a series of poly(ethylene glycol) (PEG) networks consisting of well-defined branched precursors. The PEG networks were prepared by drying gels synthesized at various conditions. The PEG networks showed slower crystallization with lower final crystallinity than uncrosslinked PEGs with amine end groups. Surprisingly, the effect of network formation was not as significant as that of the relatively bulky end-groups introduced in the uncrosslinked polymer. The molecular weight of the precursor PEG, or equivalently the chain length between neighboring junctions, was the primary parameter that affected the crystallization of the PEG networks. Shorter network chains led to lower crystallization rates and final crystallinity. This effect became less significant as the network chain length increased. On the other hand, the spatial and topological defects formed in the gel synthesis process did not affect the crystallization in the polymer networks at all. The crystallization in the polymer networks seems insensitive to these mesoscopic defects and can be solely controlled by the chain length between junctions.
Collapse
Affiliation(s)
- Masashi Ohira
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8685, Japan
| | - Shintaro Nakagawa
- Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Ryotaro Sampei
- Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Takako Noritomi
- Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Takamasa Sakai
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8685, Japan
| | - Mitsuhiro Shibayama
- Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), 162-1 Shirakata, Tokai, Naka, Ibaraki, 319-1106, Japan
| | - Xiang Li
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021, Japan.
| |
Collapse
|
2
|
Chen K, Li SF, Muthukumar M. Boundaries of the Topologically Frustrated Dynamical State in Polymer Dynamics. ACS Macro Lett 2022; 11:699-705. [PMID: 35570804 DOI: 10.1021/acsmacrolett.2c00019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Using fluorescence microscopy and single-particle tracking, we have directly observed the dynamics of λ-DNA trapped inside poly(acrylamide-co-acrylate) hydrogels under an externally applied electric field. Congruent with the recent discovery of the nondiffusive topologically frustrated dynamical state (TFDS) that emerges at intermediate confinements between the traditional entropic barrier and reptation regimes, we observe the immobility of λ-DNA in the absence of an electric field. The electrophoretic mobility of the molecule is triggered upon application of an electric field with strength above a threshold value Ec. The existence of the threshold value to elicit mobility is attributed to a large entropic barrier, arising from many entropic traps acting simultaneously on a single molecule. Using the measured Ec which depends on the extent of confinement, we have determined the net entropic barrier of up to 130 kBT, which is responsible for the long-lived metastable TFDS. The net entropic barrier from multiple entropic traps is nonmonotonic with the extent of confinement and tends to vanish at the boundaries of the TFDS with the single-entropic barrier regime at lower confinements and the reptation regime at higher confinements. We present an estimate of the mesh size of the hydrogel that switches off the nondiffusive TFDS and releases chin diffusion in the heavily entangled state.
Collapse
Affiliation(s)
- Kuo Chen
- Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Siao-Fong Li
- Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - M. Muthukumar
- Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States
| |
Collapse
|
3
|
Nakagawa S, Yoshie N. Star polymer networks: a toolbox for cross-linked polymers with controlled structure. Polym Chem 2022. [DOI: 10.1039/d1py01547h] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The synthesis of precisely controlled polymer networks has been a long-cherished dream of polymer scientists. Traditional random cross-linking strategies often lead to uncontrolled networks with various kinds of defects. Recent...
Collapse
|
4
|
Liu C, Kubo T, Otsuka K. Specificity recognition for a target protein, cytochrome c using molecularly imprinted hydrogels. J Mater Chem B 2022; 10:6800-6807. [DOI: 10.1039/d2tb00501h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Protein imprinted hydrogel, which is one form of protein imprinted molecularly imprinted polymers (MIPs), is an important material for enzyme-linked immunosorbent assay, drug delivery materials, sensors, separation materials, etc. To...
Collapse
|
5
|
A benchmark for gel structures: bond percolation enables the fabrication of extremely homogeneous gels. Polym J 2021. [DOI: 10.1038/s41428-021-00479-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
6
|
Abstract
A hydrogel is a solid form of polymer network absorbed in a substantial amount of aqueous solution. In electrophoresis, hydrogels play versatile roles including as support media, sieving matrixes, affinity scaffolds, and compositions of molecularly imprinting polymers. Recently, the study of hydrogels has been advancing with unprecedented speed, and the application of hydrogels in separation science has brought new opportunities and possible breakthroughs. A good understanding about the roles and effects of the material is essential for hydrogel applications. This review summarizes the hydrogels that has been described in various modes of electrophoretic separations, including isoelectric focusing gel electrophoresis (IEFGE), isotachophoresis (ITP), gel electrophoresis and affinity gel electrophoresis (AGE). As microchip electrophoresis (ME) is one of the future trends in electrophoresis, thought provoking studies related to hydrogels in ME are also introduced. Novel hydrogels and methods that improve separation performance, facilitate the experimental operation process, allow for rapid analysis, and promote the integration to microfluidic devices are highlighted.
Collapse
Affiliation(s)
- Chenchen Liu
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University
| | - Takuya Kubo
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University
| | - Koji Otsuka
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University
| |
Collapse
|
7
|
Takashima R, Ohira M, Yokochi H, Aoki D, Li X, Otsuka H. Characterization of N-phenylmaleimide-terminated poly(ethylene glycol)s and their application to a tetra-arm poly(ethylene glycol) gel. SOFT MATTER 2020; 16:10869-10875. [PMID: 33210675 DOI: 10.1039/d0sm01658f] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Tetra-arm poly(ethylene glycol) (TetraPEG) gels are tough materials whose toughness originates from their uniform network structure. They can be formed by combining the termini of tetra-arm polymers via chemical reactions with high conversion efficiency, such as the Michael addition, condensations using an active ester group, and alkyne-azide cycloadditions. Herein, we report the synthesis of a tetra-PEG gel using a tetra-arm polymer with N-phenylmaleimide moieties at the polymer ends (tetra-N-aryl MA PEG) as a scaffold. Tetra-N-aryl MA PEG can be obtained via a simple maleimidation using the modification agent p-maleimidophenyl isocyanate (PMPI), which directly transforms the hydroxy groups at the polymer ends into reactive N-aryl maleimide groups in a one-pot reaction. The thus-obtained tetra-N-aryl MA PEG was fully characterized using high-performance liquid chromatography (HPLC), matrix-assisted laser desorption ionization time of flight mass spectrometry, and proton nuclear magnetic resonance spectroscopy. HPLC analysis not only demonstrated the high purity of tetra-N-aryl MA PEG and the full conversion of the hydroxy groups, but also provided an effective characterization method for N-aryl maleimide-based PEG using a simple protocol, which enables us quantitative analysis of functionalized polymers with different N-aryl maleimide numbers. Furthermore, we fabricated a TetraPEG gel via Michael addition of the obtained tetra-N-aryl MA and thiol-terminated TetraPEGs. Thus, this report presents the application of tetra-N-aryl MA PEG as an effective precursor to obtain a uniform network structure and a method for its characterization; these results should provide support for the development of functional molecules, soft materials, and further functional materials based on the uniform-network-structure concept.
Collapse
Affiliation(s)
- Rikito Takashima
- Department of Chemical Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan.
| | | | | | | | | | | |
Collapse
|
8
|
Ohira M, Tsuji Y, Watanabe N, Morishima K, Gilbert EP, Li X, Shibayama M. Quantitative Structure Analysis of a Near-Ideal Polymer Network with Deuterium Label by Small-Angle Neutron Scattering. Macromolecules 2020. [DOI: 10.1021/acs.macromol.9b02695] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Masashi Ohira
- Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Yui Tsuji
- Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Nobuyuki Watanabe
- Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Ken Morishima
- Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2, Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
| | - Elliot P. Gilbert
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia
| | - Xiang Li
- Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Mitsuhiro Shibayama
- Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| |
Collapse
|
9
|
You Q, Wang P, Zhang D, Li Z, Yamaguchi Y. High‐Performance Sieving Electrophoresis for Single‐Nucleotide Polymorphisms with a Structuring Hydrogel Network. MACROMOL CHEM PHYS 2019. [DOI: 10.1002/macp.201900385] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Qingxiang You
- Engineering Research Centre of Optical Instrument and SystemMinistry of EducationKey Lab of Optical Instruments and Equipment for Medical EngineeringMinistry of EducationShanghai Key Lab of Modern Optical SystemUniversity of Shanghai for Science and Technology Shanghai 200093 China
- College of Optoelectronic EngineeringChangzhou Institute of Technology No.299, Tongjiangnan Road Changzhou 213002 China
| | - Ping Wang
- Department of Clinical LaboratoryXinhua HospitalShanghai Jiao Tong University School of Medicine 1665 Kongjiang Road Shanghai 200092 China
| | - Dawei Zhang
- Engineering Research Centre of Optical Instrument and SystemMinistry of EducationKey Lab of Optical Instruments and Equipment for Medical EngineeringMinistry of EducationShanghai Key Lab of Modern Optical SystemUniversity of Shanghai for Science and Technology Shanghai 200093 China
| | - Zhenqing Li
- Engineering Research Centre of Optical Instrument and SystemMinistry of EducationKey Lab of Optical Instruments and Equipment for Medical EngineeringMinistry of EducationShanghai Key Lab of Modern Optical SystemUniversity of Shanghai for Science and Technology Shanghai 200093 China
| | - Yoshinori Yamaguchi
- Department of Applied PhysicsGraduate School of EngineeringOsaka University Osaka 5650871 Japan
- Institute of Photonics and Bio‐Medicine (IPBM)Graduate School of ScienceEast China University of Science and Technology Shanghai 200237 China
| |
Collapse
|
10
|
Hoshino KI, Nakajima T, Matsuda T, Sakai T, Gong JP. Network elasticity of a model hydrogel as a function of swelling ratio: from shrinking to extreme swelling states. SOFT MATTER 2018; 14:9693-9701. [PMID: 30460959 DOI: 10.1039/c8sm01854e] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this work, we intended to investigate the relationship between the swelling ratio Q and Young's modulus E of hydrogels from their contracted state to extreme swelling state and elucidate the underlining molecular mechanism. For this purpose, we used tetra-poly(ethylene glycol) (tetra-PEG) gel, whose network parameters are well known, as the polymer backbone, and we succeeded in tuning the swelling of the gel by a factor of 1500 times while maintaining the topological structure of the network unchanged, using an approach combining a molecular stent method and a PEG dehydration method. A master curve of Q-E, independent of the method of obtaining Q, was obtained. Using the worm-like chain model, the experimentally determined master curve can be well reproduced. We also observed that the uniaxial stress-strain curve of the hydrogel can be well predicted by the worm-like chain model using the structure parameters determined from the fitting of the Q-E experimental curve.
Collapse
Affiliation(s)
- Ken-Ichi Hoshino
- Graduate School of Life Science, Hokkaido University, N21W11, Kita-ku, Sapporo, Hokkaido 001-0021, Japan
| | | | | | | | | |
Collapse
|
11
|
Tsuji Y, Li X, Shibayama M. Evaluation of Mesh Size in Model Polymer Networks Consisting of Tetra-Arm and Linear Poly(ethylene glycol)s. Gels 2018; 4:E50. [PMID: 30674826 PMCID: PMC6209252 DOI: 10.3390/gels4020050] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 05/17/2018] [Accepted: 05/25/2018] [Indexed: 11/17/2022] Open
Abstract
The structure and mechanical properties of model polymer networks consisting of alternating tetra-functional poly(ethylene glycol)s (PEGs) and bis-functional linear PEGs were investigated by dynamic light scattering and rheological measurements. The sizes of the correlation blob ( ξ c ) and the elastic blob ( ξ e l ) were obtained from these measurements and compared to the theoretical mesh size, the geometric blob ( ξ g ), calculated by using the tree-like approximation. By fixing the concentration of tetra-PEGs and tuning the molecular weight of linear-PEGs, we systematically compared these blob sizes in two cases: complete network (Case A) and incomplete network (Case B). The correlation blob, ξ c , obtained by dynamic light scattering (DLS) was found to obey the well-known concentration dependence for polymer solutions in semidilute regime ( ξ c ~ ϕ - 3 / 4 ) irrespective of the Cases. On the other hand, the G ' was strongly dependent on the Cases: For Case A, G ' was weakly dependent on the molecular weight of linear-PEGs ( G ' ~ M c 0.69 ) while G ' for Case B was a strong increasing function of M c ( G ' ~ M c 1.2 ). However, both of them are different from the geometric blob (theoretical mesh) of the gel networks. In addition, interesting relationships between G ' and ξ c , G ' ~ ξ c , G ' ~ ξ C - 2 , were obtained for Cases A and B, respectively.
Collapse
Affiliation(s)
- Yui Tsuji
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8581, Japan.
| | - Xiang Li
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8581, Japan.
| | - Mitsuhiro Shibayama
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8581, Japan.
| |
Collapse
|
12
|
Affiliation(s)
- Mitsuhiro Shibayama
- Institute for Solid State
Physics, The University of Tokyo, Kashiwanoha, Kashiwa, 277-8581, Japan
| | - Xiang Li
- Institute for Solid State
Physics, The University of Tokyo, Kashiwanoha, Kashiwa, 277-8581, Japan
| | - Takamasa Sakai
- Department of Bioengineering,
Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| |
Collapse
|
13
|
Watanabe N, Li X, Shibayama M. Probe Diffusion during Sol–Gel Transition of a Radical Polymerization System Using Isorefractive Dynamic Light Scattering. Macromolecules 2017. [DOI: 10.1021/acs.macromol.7b02202] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Nobuyuki Watanabe
- Institute
for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Xiang Li
- Institute
for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Mitsuhiro Shibayama
- Institute
for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| |
Collapse
|
14
|
Affiliation(s)
- Mitsuhiro Shibayama
- Institute for Solid State Physics; The University of Tokyo; 5-1-5 Kashiwanoha Kashiwa Chiba 277-8581 Japan
| |
Collapse
|
15
|
Li X, Watanabe N, Sakai T, Shibayama M. Probe Diffusion of Sol–Gel Transition in an Isorefractive Polymer Solution. Macromolecules 2017. [DOI: 10.1021/acs.macromol.6b02573] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xiang Li
- Institute
for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, Japan
| | - Nobuyuki Watanabe
- Institute
for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, Japan
| | - Takamasa Sakai
- Department
of Bioengineering, The University of Tokyo, Yayoi, Tokyo, Japan
| | - Mitsuhiro Shibayama
- Institute
for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, Japan
| |
Collapse
|
16
|
Khairulina K, Chung UI, Sakai T. New design of hydrogels with tuned electro-osmosis: a potential model system to understand electro-kinetic transport in biological tissues. J Mater Chem B 2017; 5:4526-4534. [DOI: 10.1039/c7tb00064b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A series of charged polymer gels with precisely controlled magnitude and direction of electro-osmotic flow was prepared and opens up the possibility for understanding the contribution of electro-osmosis to transport phenomenon in native biological tissues.
Collapse
Affiliation(s)
- Kateryna Khairulina
- Department of Bioengineering
- School of Engineering
- The University of Tokyo
- Bunkyo-ku
- Japan
| | - Ung-il Chung
- Department of Bioengineering
- School of Engineering
- The University of Tokyo
- Bunkyo-ku
- Japan
| | - Takamasa Sakai
- Department of Bioengineering
- School of Engineering
- The University of Tokyo
- Bunkyo-ku
- Japan
| |
Collapse
|
17
|
Affiliation(s)
- Chia-Chun Lin
- Department of Materials Science
and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6272, United States
| | - Emmabeth Parrish
- Department of Materials Science
and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6272, United States
| | - Russell J. Composto
- Department of Materials Science
and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6272, United States
| |
Collapse
|
18
|
Khairulina K, Li X, Nishi K, Shibayama M, Chung UI, Sakai T. Electrophoretic mobility of semi-flexible double-stranded DNA in defect-controlled polymer networks: Mechanism investigation and role of structural parameters. J Chem Phys 2015; 142:234904. [PMID: 26093576 DOI: 10.1063/1.4922367] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Our previous studies have reported an empirical model, which explains the electrophoretic mobility (μ) of double-stranded DNA (dsDNA) as a combination of a basic migration term (Rouse-like or reptation) and entropy loss term in polymer gels with ideal network structure. However, this case is of exception, considering a large amount of heterogeneity in the conventional polymer gels. In this study, we systematically tune the heterogeneity in the polymer gels and study the migration of dsDNA in these gels. Our experimental data well agree with the model found for ideal networks. The basic migration mechanism (Rouse-like or reptation) persists perfectly in the conventional heterogeneous polymer gel system, while the entropy loss term continuously changes with increase in the heterogeneity. Furthermore, we found that in the limit where dsDNA is shorter than dsDNA persistence length, the entropy loss term may be related to the collisional motions between DNA fragments and the cross-links.
Collapse
Affiliation(s)
- Kateryna Khairulina
- Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Xiang Li
- Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Kengo Nishi
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Mitsuhiro Shibayama
- Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Ung-il Chung
- Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Takamasa Sakai
- Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| |
Collapse
|