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 Materials scientist creates fabric alternative to batteries for wearable devices
12.11.2018 | University of Massachusetts at Amherst

nachricht A new path through the looking-glass
12.11.2018 | Deutsches Elektronen-Synchrotron DESY

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

Im Focus: Nanorobots propel through the eye

Scientists developed specially coated nanometer-sized vehicles that can be actively moved through dense tissue like the vitreous of the eye. So far, the transport of nano-vehicles has only been demonstrated in model systems or biological fluids, but not in real tissue. The work was published in the journal Science Advances and constitutes one step further towards nanorobots becoming minimally-invasive tools for precisely delivering medicine to where it is needed.

Researchers of the “Micro, Nano and Molecular Systems” Lab at the Max Planck Institute for Intelligent Systems in Stuttgart, together with an international...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

In focus: Peptides, the “little brothers and sisters” of proteins

12.11.2018 | Life Sciences

Materials scientist creates fabric alternative to batteries for wearable devices

12.11.2018 | Materials Sciences

A two-atom quantum duet

12.11.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>