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Stretching the limits of high conductivity~High-performing elastic conductor
realized by self-forming Ag nanoparticles~
School of Engineering, The University of TokyoJapan Science and Technology Agency (JST)
RIKENPress releaseMay 11th, 2017
Prof. Takao SomeyaDr. Naoji Matsuhisa
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Contents
(1) New printable elastic conductors(2) Background, Impact, Future prospect
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The result will be published in Nature Materialson 15 May 2017 at 16:00 (GMT) / 11:00 (EST), which is when the embargo will be lifted.
Summary
We have developed printable elastic conductors with the world’s highest conductivity (935 S/cm) at a strain of 400% (5 times as long as the original length).
The high performance was obtained by in situ formation of Ag nanoparticles, which resulted by mixing micrometer-sized Ag flakes and a fluorine rubber.
The new material realizes simple integration of stretchable pressure/temperature sensors on textiles, leading to applications in sports wear or robotics. 3
World’s Best Printable Elastic Conductors
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Formed by a simple printing process.High conductivity (935 S/cm) and stretchability
(400%) are simultaneously obtained.
伸張率
伸張率
World best printable elastic conductors (Movie)
High conductivity is maintained at very large strains, enabling the stable operation of LEDs. 5
Pressuresensor
New printedelastic conductors
Lightemittingdiodes(LEDs)
Stretchable Sensors Fabricated on Textiles
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The pressure is sensed at the fingertips and the brightness of the LEDs changes with the applied pressure.
Main features
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Printable (e.g. screen printing, stencil
printing)
Without strain, the materials show a high
conductivity of 4972 S/cm.
With 400% strain (5 times as long as the
original length), the materials exhibit a world’s
highest conductivity of 935 S/cm.
Fabrication process
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Organic solvent(Methylisobutylketone)
Ag flakes
Fluorine rubber(DAI-EL, Daikin Industries)
Elastic conductor ink
Fluorine surfactant
Mix
The printed tracesare dried at 80 ℃ for1 h and 120 ℃ for 1 h.
100 nm
Self-formation of Ag nanoparticlesboosts the performance.
(Transmission electron microscope (TEM) image)
Ag flakes
~8-nm Ag nanoparticles are self-formed in high density.
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The Ag nanoparticles observation was conducted in collaboration with Dr. Daisuke Hashizume, and Mr. Daishi Inoue at RIKEN.
Performance Improvement by Self-Formed Ag Nanoparticles
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100
101
102
103
104
0 50 100 150 200 250 300
Con
duct
ivity
(S/c
m)
Strain (%)
With self-formed Ag nanoparticles
With dry Agnanoparticlepowder
Self-formation of Ag nanoparticles realizeshigh-performance elastic conductors.
101
102
103
104
0 100 200 300 400 500
Con
duct
ivity
(S/c
m)
Strain (%)
Comparison With Previous Studies[1] T. Sekitani, et al. Nat. Mater.
8, 494–499 (2009).[2] K. Chun, et al. Nat. Nanotechnol.
5, 853–857 (2010).[3] T. Araki, et al. IEEE EDL
32, 1424–1426 (2011).[5] M. Park, et al. Nat. Nanotechnol.
7, 803–809 (2012).[6] Y. Kim, et al. Nature
500, 59–63 (2013).[7] H. Stoyanov, et al. Adv. Mater.
25, 578–83 (2013).[8] R. Ma, et al. ACS nano 9,
10876-10886 (2015).[9] J. Liang et al. Adv. Mater. 28,
5986-5996 (2016).[10] N. Matsuhisa, et al.
Nat. Commun. 6, 7461 (2015).
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2015
At 400% strain, the world’s highest conductivity(935 S/cm) is achieved. (Without strain, 4972 S/cm)
2017 (This study)New elasticconductor
2009
Installation of stretchable sensors to textiles
2 cm
Large area sensors are easily integrated in textile.
Heat & Press
Fully Printed Stretchable Sensor Sheet (※Temperature sensors can also be fabricated.)
Textilesubstrate Elastic
conductorwiring
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Pressure Sensors
2 cm
Stretchable pressure sensing textile glove
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Sensors can be easily installed to the moving parts of robots.
Elastic Conductors Pressure Sensors
2 cm
5 mm
~120% strain
Resist/Polyurethane
Stretch test of stretchable pressure sensors
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Elastic conductor maintains high conductivity at 250% strain. Stable measurement of pressure.
Pressuresensor
Elastic conductor
2 cm102
103
104
105
106
107
108
0 1 2 3 4 5 6
0%250%
Res
ista
nce
()
Force (N)
Applied strain (%)
250%strain
Mechanism of Ag nanoparticles self-formation
Ag flake
Fluorine rubber+ fluorine surfactant
Ag2O layer
Ag+
Ag+
Ag+
Ag+
Ag+
Ag+
Self-formedAg nanoparticles
Heat
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Ag flakes are dispersed in the rubber. The surfactant and addition of heat convert the ions to Ag nanoparticles.
Research backgroundImpact
Future prospect
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Stretchable electronics
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Stretchable electronic devices(on Textiles, Rubber sheets)Electronics on soft, arbitrary surfaces.
A stretchable wiring with high conductivity and stretchability has been crucial in stretchable devices.
Smart sheet,Smart handle
Automobile
RobotSportTraining,
Injury prevention
MedicalBody
temperature,EMG, ECG
VR・ARHuman computer interfaces
Artificial feeling
Lamination to: Human
Artificial skin/muscle,Soft robots
To: Machine
Development of Elastic Conductors
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Year 2008 2009 2015 2017(This study)
Conductivity(S/cm) 57 102 182 935
Stretchability(%) 40 118 215 400
Conductive filler(s)
Carbonnanotubes
Carbonnanotubes
Ag flakes
Ag flakes Ag
nanoparticles
PaperT. Sekitani,
T. Someya, et al. Science 321,1468 (2008).
T. Sekitani, T. Someya, et al.
Nature Materials 8,494 (2009).
N. Matsuhisa, T. Someya, et
al. Nature Communicatio
ns 6, 7461 (2015).
N. Matsuhisa, T. Someya, et al. Nature
Materials (2017).
10 years improvement in conductivity (16 times) and stretchability (10 times).
Future prospect
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Stretchable sensors can be easily attached to soft, arbitrary surfaces.
Various applications include vital information monitoring of the whole body using wearables, and artificial feelings. They will accelerate the fields of sports, healthcare, medical, and robotics.
The self-formation of metal nanoparticles will enhance the performance of various composite materials which include elastic conductors, pressure sensors, and temperature sensors.
Further developments for the practical use
1. Cyclic durability
2. Environmental stabilityeg. Washability, Thermal Stability
3. System level integrationeg. Power Supply, Wireless Communication
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Publication and press embargoThe result will be published in Nature Materialson 15 May 2017 at 16:00 (GMT) / 11:00 (EST), which is when the embargo will be lifted.
Title“Printable Elastic Conductors by in situ Formation of Silver Nanoparticles from Silver Flakes”
AuthorsNaoji Matsuhisa, Daishi Inoue, Peter Zalar, HanbitJin, Yorishige Matsuba, Akira Itoh, Tomoyuki Yokota, Daisuke Hashizume, and Takao Someyadoi: 10.1038/NMAT4904
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Funding
This result is an accomplishment of the Exploratory Research for Advanced Technology (ERATO) research funding program.
Project Name:Someya Bio-Harmonized Electronics Project
Project Director:Takao Someya, Professor, School of Engineering, The University of Tokyo
Project Period:August 2011 - March 2017
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Summary The new printable elastic conductor is 400%
stretchable (5 times as long as the original length), and exhibits the world’s highest conductivity at strains >150%.
The self-formation of Ag nanoparticles boosted the performance of the elastic conductors, which are not originally included in the ink.
Highly stretchable (>250%) pressure/temperature sensors are fully fabricated by printing processes.
The new material will be fully utilized in wearables or artificial skins, with applications in sports, healthcare, medical, and robots. 23
Contact
Professor Takao Someya
Department of Electrical Engineering and Information Systems (EEIS), Graduate School of Engineering, The University of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 JAPANSomeya Laboratory, School of Engineering, University of Tokyo
Tel: +81-3-5841-6756Fax: +81-3-5841-6709Email: someya@ee.t.u-tokyo.ac.jp
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