Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New study helps explain the surprising behavior of tiny 'artificial muscles'

29.04.2010
Using neutron beams and atomic-force microscopes, a team of university researchers working with the National Institute of Standards and Technology (NIST) may have resolved a 10-year-old question about an exotic class of "artificial muscles"—how do they work? Their results* could influence the design of future specialized robotic tools.

These "artificial muscles," first demonstrated in the early 1990s, are "ionic polymer metal composite" (IPMC) actuators, a thin polymer strip plated on both surfaces with conducting metal. The basic unit of the polymer molecule has a charged component attached to it (hence, "ionic"), and it forms a sort of open, permeable structure that can be soaked with water molecules and oppositely charged ions. A modest electric charge across the metalized surfaces will cause the strip to flex in one direction; an alternating charge will make it wiggle like a fish's tail. But why?

"There has been a lot of debate as to the mechanism of actuation in these kinds of systems," says NIST materials scientist Kirt Page. One possibility was that the electric charge on the metalized faces causes the polymer and the free ions to reorient themselves next to the metal, stretching one side and contracting the other. But using a neutron beam at the NIST Center for Neutron Research (NCNR) to watch an IPMC in action as it wiggled back and forth, the team found something very different. Neutrons are particularly good for mapping the locations of water molecules, and they showed that a major force in the actuator is hydraulics. "The water and ions move to one electrode swelling one side and dehydrating the other, causing that to contract, and it bends in that direction," explains Virginia Tech professor Robert Moore, who directed the research. "Then you flip the potential, the ions come screaming back—positive ions again moving towards the new negative electrode—and you can go back and forth."

It happens surprisingly fast, according to Page. "People weren't quite convinced that water could actually move over these distances that quickly," he says, "This paper is the first to show that in fact, this gradient in the water concentration is established almost instantaneously."

A better understanding of just how IPMC actuators work could allow researchers to engineer better materials of this type with improved performance. Current actuators can be small and light-weight, and they can flex over relatively large distances, but the force they can generate is low so these "muscles" are not very strong, according to Moore. They could be used in microfluidic systems as pumps or valves, as tiny robotic grippers in applications where other actuators are impractical or even, says Moore, "as actual artificial muscles in living tissues. I think we're still in the infancy stage of using these. There are still quite a number of details about the mechanism that we need to unlock."

* J.K. Park, P.J. Jones, C. Sahagun, K.A. Page, D.S. Hussey, D.L. Jacobson, S.E. Morgan and R.B. Moore. Electrically stimulated gradients in water and counterion concentrations within electroactive polymer actuators Soft Matter. 2010. 6. 1444�. DOI: 10.1039/b922828d.

Michael Baum | EurekAlert!
Further information:
http://www.nist.gov

More articles from Studies and Analyses:

nachricht The Great Unknown: Risk-Taking Behavior in Adolescents
19.01.2017 | Max-Planck-Institut für Bildungsforschung

nachricht A sudden drop in outdoor temperature increases the risk of respiratory infections
11.01.2017 | University of Gothenburg

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland

19.01.2017 | Earth Sciences

Not of Divided Mind

19.01.2017 | Life Sciences

Molecule flash mob

19.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>