Artificial nacre developed.

Scientists have discovered how to recreate the solid yet flexible properties of nacre (mother-of-pearl) in the lab. This new technology could lead to developments in body armor, artificial body parts, and protective coatings that need both strength and flexibility.

Researchers at Oklahoma

State University have created a layered material at the microscopic level that comes close to recreating nacre's properties, including its iridescence. Natural nacre owes much of its strength to an internal brick-like structure. Protein layers only nanometers thick provide the pliable "mortar," while calcium carbonate (the principal chemical in limestone) comprises the solid "bricks."

In artificial nacre, platelets of negatively charged clay called montmorillonite provide the bricks, while fibers of a positively charged polyelectrolyte serve as the mortar. The opposite charges help the two components bond tightly to form the nacre structure. Unique bonds hold the polymer chains to each other in a special way that maintains strength and flexibility.

Researchers created the artificial nacre by immersing a glass slide in alternating baths of clay and polymer. A robotic device performed the 200 dips, with each dip producing several layers averaging 24 nanometers thick.

Because of its strong, lightweight, and flexible features, artificial nacre may serve as a biocompatible substrate for growing human tissue, organs, or bones.

Source: National Science Foundation, Office of Legislative and Public Affairs, 4201 Wilson Boulevard, Arlington, Virginia 22230. Web site www.nsf.org.