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 Decoding cement's shape promises greener concrete
08.12.2016 | Rice University

nachricht Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D
08.12.2016 | DOE/Brookhaven National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

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...

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

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>