Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The seashell´s inner beauty

28.05.2003


Scanning electron micrograph of artificial nacre developed by researchers at Oklahoma State University and Digital Instruments/Veeco. One micron is one millionth of a meter.
Credit: Zhiyong Tang, Oklahoma State University; NSF


Photograph depicting artificial nacre and revealing the material’s thin texture and iridescence.
Credit: Zhiyong Tang, Oklahoma State University; NSF


There is more to mother-of-pearl than good looks. Also called nacre, the gleaming, white material is renowned in scientific circles for its strong, yet flexible, properties. Now researchers have developed a nanoscale, layered material that comes close to nacre’s properties, including its iridescence.

The ability to nanomanufacture artificial nacre may provide lightweight, rigid composites for aircraft parts, artificial bone and other applications.

Reporting online in Nature Materials on May 25, Nicholas Kotov and his colleagues at Oklahoma State University and at Digital Instruments/Veeco describe their method for creating nacre-like material that consists of alternating layers of clay and a type of polymer called a polyelectrolyte. Kotov received a National Science Foundation (NSF) CAREER Award to pursue the work.



"The discovery allows researchers to tailor flexible materials to a given application-to get the tough materials that nature has been able to produce," said Lynn Schneemeyer, the NSF program officer who oversees Kotov’s award. NSF is an independent federal agency that supports fundamental research and education across all fields of science and engineering.

Natural nacre owes much of its strength and flexibility to an internal brick-like structure. Protein layers only nanometers (billionths of a meter) thick provide the pliable "mortar," while calcium carbonate, the principal chemical in limestone and antacids, comprises the similarly miniscule "bricks" adding hardness.

In the artificial nacre, platelets of a negatively-charged clay called montmorillonite provide the bricks while fibers of a positively-charged polyelectrolyte called poly(diallydimethylammonium) chloride (PDDA) serve as the mortar. The opposite charges help the two components bond tightly to form the nacre structure.

"The combination of montmorillonite and PDDA for nacre modeling came to us quite naturally," said Kotov. "It was the very first clay-polyelectrolyte system I worked with a few years back." He also states that the montmorillonite has several advantages over other layered minerals, such as talc, including an ability to disperse easily in water, while the PDDA has a high affinity for clays.

Unique "sacrificial bonds" hold the polymer chains to each other in a special way that maintains strength and flexibility. The bond is a result of the polymer interacting with negative charges on the clay surfaces (or, in the case of real nacre, proteins interacting with positive calcium ions).

Such ionic bonds are strong and absorb energy when the artificial nacre is deformed. If the bonds break, they can reform when the stress goes away. They are dubbed "sacrificial" because they take the brunt of an attack, leaving the covalent bonds in the molecules intact.

The artificial nacre was created by immersing a glass slide in alternating baths of clay and polymer. A robotic device performed the 200 dips, with each dip producing several plastic clay layers-each clay and plastic layer is, on average, only 24 nanometers thick.

"It is a very robust preparation and produces beautiful layers every time," said Kotov.

Because of the artificial nacre’s potential for highstrength, protective coatings such as body armor and biocompatible substrates for growing human tissue or organs, Kotov and his colleagues are working with a company to further develop the material and techniques. And, because researchers can easily add new components like ultraviolet light- or corrosion resistant chemicals to the artificial nacre, the same manufacturing process can produce materials for a variety of applications.

Josh Chamot | NSF
Further information:
http://www.nsf.gov
http://www.nsf.gov/od/lpa/news/media/start.htm
http://www.nsf.gov/od/lpa

More articles from Materials Sciences:

nachricht Robust and functional – surface finishing by suspension spraying
19.09.2017 | Fraunhofer-Institut für Keramische Technologien und Systeme IKTS

nachricht Graphene and other carbon nanomaterials can replace scarce metals
19.09.2017 | Chalmers University of 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: 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...

Im Focus: Silencing bacteria

HZI researchers pave the way for new agents that render hospital pathogens mute

Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...

Im Focus: Artificial Enzymes for Hydrogen Conversion

Scientists from the MPI for Chemical Energy Conversion report in the first issue of the new journal JOULE.

Cell Press has just released the first issue of Joule, a new journal dedicated to sustainable energy research. In this issue James Birrell, Olaf Rüdiger,...

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

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

19.09.2017 | Event News

New quantum phenomena in graphene superlattices

19.09.2017 | Physics and Astronomy

A simple additive to improve film quality

19.09.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>