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 New biomaterial could replace plastic laminates, greatly reduce pollution
21.09.2017 | Penn State

nachricht Stopping problem ice -- by cracking it
21.09.2017 | Norwegian University of Science and Technology

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Comet or asteroid? Hubble discovers that a unique object is a binary

21.09.2017 | Physics and Astronomy

Cnidarians remotely control bacteria

21.09.2017 | Life Sciences

Monitoring the heart's mitochondria to predict cardiac arrest?

21.09.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>