Artificial materials imitate nature's own.

Nature has a knack for making materials. Bones and teeth, for instance, display extraordinary properties-high strength, light weight, and unusual molecular architecture-that scientists find hard to replicate. Even more remarkable is the ability of biologi cal processes to assemble these complex composites from inorganic materials.

Using a process of molecular self-assembly inspired by the way bones form, chemists Peter T. Tanev and Thomas J. Pinnavaia of Michigan State University in East Lansing have managed to coax a silicon compound into forming tiny onionlike beads, called vesic les, that are layered in concentric shells.

"We're aiming to mimic the way nature puts together organic and inorganic components, as in teeth and bones," says Pinnavaia.

"By using a biological type of assembly, we've been able to make a new type of porous material."

The newly fabricated material resembles zeolites, naturally occurring mineral compounds that serve as catalysts for a wide range of reactions. Scientists want to customize such materials, tailoring the size and shape of their pores to specific chemical pu rposes.

"Materials that have holes as part of their structure, such as zeolites, play an important role in commercial processes, particularly in refining petroleum and in reducing industrial pollutants," Pinnavaia says. "The chemistry of assembly of these porous silica vesicles resembles what goes on during biomineralization."

The new vesicles-which form clusters resembling a bunch of grapes-measure between one-millionth and one-billionth of a meter in diameter, the chemists report in the March 1 Science.

Tests show that this silica remains stable at a wide range of temperatures, has a large surface area and pore volume, and can be produced using methods that are environmentally benign, the chemists say.

"The ability to make complex self-assembled materials like this is a significant advance," says Thomas Bein, a chemist at Purdue University in West Lafayette, Ind.

"This is one of the first examples of an organized, porous material with a vesicle structure," says Galen D. Stucky, a chemist at the University of California, Santa Barbara. "That's an important contribution."

With further development, such biomimetic materials hold the promise of spawning improved building materials, novel protective coatings, and components for automobiles and microelectronics.