Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Polymer Foams as Charge Carriers

04.08.2003


Scanning electron microscope picture of a ferroelectretic foam, together with a graphical representation of the charging states in the pores.


A research team in Austria has been unravelling the secrets of the charging of plastic foams. Its findings open the way for the development of flat microphones and loudspeakers, as well as "smart" surfaces that could be used as floor coverings, among other things. The interest in the success of the group´s work - which was co-funded by the Austrian Science Fund (FWF) - has resulted in the integration of the project in a European interdisciplinary research network.

During a thunder storm the electrical tension between the earth and the air is discharged by the lightning and hence lowered. In non-polar polymer foams a comparable process results in the precise opposite - an increase in the electrical charge. First, an electric discharge is induced in the microscopic voids (pores) in foamed plastics by applying an external voltage. The propagation of the discharge is then inhibited by the insulating properties of the polymer foam, resulting in charging of the pore walls. As the non-polar material is non-conductive, the charge is stored there. A team under Prof. Siegfried Bauer at the Johannes Kepler University Linz Institute for Experimental Physics has succeeded in proving the existence of this phenomenon. In so doing it has challenged established scientific doctrine which holds that such states can only exist in polar materials.

Pores with potential



The opposing positive and negative poles in the pores of the foam create an electrical potential. If the charged polymers are compressed, the gap between the two poles in the pore walls narrows, exciting an electrical signal. The transformation of pressure into an electrical signal that can be amplified and modulated enables polymers to be used as sensors, e.g. for "intelligent" floor coverings that "report" falls at senior citizens´ homes.

Changes in air pressure (acoustic oscillations) can also be converted into electrical signals in this way. As the polymers are easy to make and can be varied in many ways, they hold out the prospect for the development of inexpensive, high-quality flat microphones and loudspeakers. Identifying suitable materials was one of the aims of the project.

Nomen est omen

In the course of the project the team succeeded in describing an unexpected property of the plastic foams it was using: patterned charging is possible, and the polarity in the pores can thus be switched. As these are the first known materials to combine this property with an ability to store charges, Prof. Bauer created the new term "ferroelectret" to describe them. "What makes ferromagnets important is the fact that their polarity can be switched", Bauer explained. "Materials that store charges are referred to as `electrets´. The term coined by us for these polymer foams refers to their ability to combine these two characteristics."

Europe in the lead

The international significance of the ferroelectrets is reflected in the research collaborations in which the Linz group is involved. During the project cooperation agreements were concluded with universities in Darmstadt, Potsdam (Ger) and Tampere (Fi). "Today", said Bauer, "we are part of a pan-European network that also includes a number of firms." The global importance of this alliance will be reflected next October when ferroelectrets will be a topic at an international symposium held by America´s Institute of Electrical and Electronics Engineers (IEEE). The discovery and the team responsible for it will be the subject of an invited lecture. This recognition is proof of the global lead enjoyed by the project, and the new European network of experimental physicists, engineers and materials scientists that FWF funding helped establish.

Contact: Univ.-Prof. Dr. Siegfried Bauer, sbauer@jku.at, Tel. +43-732-2468-9241

Univ.-Prof. Dr. Siegfried Bauer | alfa
Further information:
http://www.fwf.ac.at/en/press/tension.html

More articles from Materials Sciences:

nachricht Simple processing technique could cut cost of organic PV and wearable electronics
06.12.2016 | Georgia Institute of Technology

nachricht InLight study: insights into chemical processes using light
05.12.2016 | Fraunhofer-Institut für Lasertechnik ILT

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Simple processing technique could cut cost of organic PV and wearable electronics

06.12.2016 | Materials Sciences

3-D printed kidney phantoms aid nuclear medicine dosing calibration

06.12.2016 | Medical Engineering

Robot on demand: Mobile machining of aircraft components with high precision

06.12.2016 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>