Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Elastic Electronics: Stretchable Gold Conductor Grows Its Own Wires

19.07.2013
Networks of spherical nanoparticles embedded in elastic materials may make the best stretchy conductors yet, engineering researchers at the University of Michigan have discovered.

Flexible electronics have a wide variety of possibilities, from bendable displays and batteries to medical implants that move with the body.


Courtesy of Nicholas Kotov

LEFT: an electron microscope image of the gold nanoparticles in a relaxed sample of the layer-by-layer material. The nanoparticles are dispersed. RIGHT: a similar sample stretched to a little over twice its original length, at the same magnification. The nanoparticles form a distinct network

"Essentially the new nanoparticle materials behave as elastic metals," said Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Engineering. "It's just the start of a new family of materials that can be made from a large variety of nanoparticles for a wide range of applications."

Finding good conductors that still work when pulled to twice their length is a tall order — researchers have tried wires in tortuous zigzag or spring-like patterns, liquid metals, nanowire networks and more. The team was surprised that spherical gold nanoparticles embedded in polyurethane could outcompete the best of these in stretchability and concentration of electrons.

"We found that nanoparticles aligned into chain form when stretching. That can make excellent conducting pathways," said Yoonseob Kim, first author of the study to be published in Nature on July 18 and a graduate student in the Kotov lab in chemical engineering.

To find out what happened as the material stretched, the team took state-of-the-art electron microscope images of the materials at various tensions. The nanoparticles started out dispersed, but under strain, they could filter through the minuscule gaps in the polyurethane, connecting in chains as they would in a solution.

"As we stretch, they rearrange themselves to maintain the conductivity, and this is the reason why we got the amazing combination of stretchability and electrical conductivity," Kotov said.

The team made two versions of their material—by building it in alternating layers or filtering a liquid containing polyurethane and nanoparticle clumps to leave behind a mixed layer. Overall, the layer-by-layer material design is more conductive while the filtered method makes for extremely supple materials. Without stretching, the layer-by-layer material with five gold layers has a conductance of 11,000 Siemens per centimeter (S/cm), on par with mercury, while five layers of the filtered material came in at 1,800 S/cm, more akin to good plastic conductors.

The eerie, blood-vessel-like web of nanoparticles emerged in both materials upon stretching and disappeared when the materials relaxed. Even when close to its breaking point, at a little more than twice its original length, the layer-by-layer material still conducted at 2,400 S/cm. Pulled to an unprecedented 5.8 times its original length, the filtered material had an electrical conductance of 35 S/cm—enough for some devices.

Kotov and Kim chiefly see their stretchable conductors as electrodes. Brain implants are of particular interest to Kotov.

"They can alleviate a lot of diseases—for instance, severe depression, Alzheimer's disease and Parkinson's disease," he said. "They can also serve as a part of artificial limbs and other prosthetic devices controlled by the brain."

Rigid electrodes create scar tissue that prevents the electrode from working over time, but electrodes that move like brain tissue could avoid damaging cells, Kotov said.

"The stretchability is essential during implantation process and long-term operation of the implant when strain on the material can be particularly large," he said.

Whether in the brain, heart or other organs—or used for measurements on the skin—these electrodes could be as pliable as the surrounding tissue. They could also be used in displays that can roll up or in the joints of lifelike "soft" robots.

Because the chain-forming tendency of nanoparticles is so universal many other materials could stretch, such as semiconductors. In addition to serving as flexible transistors for computing, elastic semiconductors may extend the lives of lithium-ion batteries. Kotov's team is exploring various nanoparticle fillers for stretchable electronics, including less expensive metals and semiconductors.

Kotov is a professor of chemical engineering, biomedical engineering, materials science and engineering and macromolecular science and engineering.

The study is titled "Stretchable Nanoparticle Conductors with Self-Organized Conductive Pathways." The work is funded by the STX foundation in Seoul, South Korea; U.S. Department of Energy's Office of Science; Defense Advanced Research Projects Agency; Air Force Office of Scientific Research; and National Science Foundation. U-M is pursuing patent protection for the intellectual property and seeking commercialization partners to help bring the technology to market.

Watch and embed the video at www.youtube.com/watch?v=KQ7_TPSSfys.

Nicole Casal Moore | Newswise
Further information:
http://www.umich.edu

More articles from Materials Sciences:

nachricht The stacked colour sensor
16.11.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

nachricht Counterfeits and product piracy can be prevented by security features, such as printed 3-D microstructures
16.11.2017 | Karlsruher Institut für Technologie (KIT)

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>